I’m a mechanic and fuel-related issue is amongst the most common ATV performance issues. You are in the right place for fuel pump testing and diagnosis, very shortly we’ll have this figured out.

There are five common ways to check if an ATV fuel pump is in good working order, they include:

1. Listen for pump sound
2. Check power at the pump
3. Check pump resistance
4. Visually check pump flow
5. Use fuel pressure gauge to test system pressure

In this post, we’ll cover faulty ATV fuel pump symptoms. We’ll cover the range of fuel pump tests open to you, and how to execute them. We’ll also cover fuel pump replacement.

Symptoms of Faulty ATV Fuel Pump

Because some electric fuel pumps don’t fail completely, the range of symptoms can vary. The most common symptom is as you guessed a no start and in many ways, a no-start is easier to diagnose than a poor performance issue. Anyhow here is a list of the most common symptoms associated with a fuel pump issue:

• No-start
• Extended crank (hard starting) (may also be caused by pump check valve)
• Idles but won’t take rev
• Poor top-end performance
• Starts then dies

If you have one or more of these symptoms we’ll suspect a faulty pump. But before we start ordering parts we’ll need to confirm our suspicions and that’s what we’ll do next.

ATV Fuel Pump Type

Not all ATVs have a fuel pump fitted some smaller older ATVs employ gravity feed. However, if your bike has a fuel pump then it will be either mechanical or electric.

Mechanical pump – Mechanical fuel pumps are fitted to older carburetor bikes. They usually employ a pulsing engine vacuum and a diaphragm to move gas from the tank to the carburetor.

Electric fuel pump – Most modern ATVs are fuel injected and therefore require higher fuel pressure which means they are fitted with an electric fuel pump. The pump is located inside the gas tank itself.

We will diagnose both mechanical and electric pumps in this post.

How to Diagnose ATV Electric Fuel Pump

An electric pump is as you know submerged inside the gas tank and usually requires tank cover and side shrouds etc removed before we can access the pump, fuel line, or wiring terminal block connector. That’s an investment of time and energy and so we’ll run a simple listening test first to confirm we have a fuel pump issue before pulling our bike apart needlessly.

Obviously, if our pump fails this first test we’ll need to strip a few covers.

Listen for pump sound

This test is simple, but you will need a charged battery and somewhere quiet to perform the test. Most electric fuel pumps emit an audible buzz or hum sound for about 3 seconds when the ignition is turned on initially. The pump does this so as to pressurize the fuel line and prime the fuel injector in preparation for starting.

The first test is simple then, turn the ignition switch on (position 2) and listen.

Two results are possible:

1 You hear a humming sound – Hearing the fuel pump hum, is a good sign, it means the wiring circuit and ECU are all doing their job, it also means the pump is working. and if you are chasing a no-start problem, the fuel pump likely isn’t the root cause.

But a hum from the pump doesn’t necessarily mean the pump is working as it should. The pump may not be supplying enough flow and that’s a common cause of symptoms such as extended crank or poor performance. If that is the type of problem you are chasing, we’ll need to remove some covers and access the pump for some testing.

2 You don’t hear a humming sound – There may be a few reasons you don’t hear the pump. The most common reasons are: the pump may indeed be faulty or the fuel pump fuse may be blown.

Since checking the fuse is a ton easier than pulling covers etc and checking the pump, we’ll check the fuse first.

Fuses commonly blow because:

• Amp rating too small
• Circuit short
• Faulty fuel pump

Some ATV fuses are located under the seat but you may need to consult your manual for fuel pump fuse location and fuse amp rating.

Check power at the pump

Ok, you already know you’ll need to strip out covers, etc to gain access to the pump terminal block connector. When you have gained access we’ll need a DVOM or test light to check for voltage. If you need tools for the job, check out the tools I use here on the ATV tools page.

The process is as follows:

• Locate and disconnect pump block connector

• Probe power and ground terminals (careful not to damage the terminals)

The power will only be present for 3 sec after ignition in position 2

Two results are possible:

1 You have power at the terminal, if so jump ahead to the resistance test here.

2 No power at the pump terminal, check power and ground independently using a test light.

Test power at the pump using the battery ground as per the picture.

The power will only be present for 3 sec after ignition in position 2

Test ground at the pump using the battery positive as per the picture.

The power will only be present for 3 sec after ignition in position 2

If you are missing either power or ground suspect a wiring break and chase them.

Check pump resistance

A resistance test is useful as it allows us to ascertain the pump circuit without having to remove it from the tank. When running a resistance test you must isolate the component from the circuit.

When testing resistance the meter sends a small charge down one side of the circuit and the second probe measures its progress.

Test as follows:

Set the DVOM to resistance Ω and probe both sides of the pump terminals.

Two results are possible:

Meter offers a resistance reading – A reading in the region of 6 ohms is typical but all bikes will have their own window of operation. You’ll need to check your reading is within it.

Meter offers an open reading – An open means the pump has an open circuit and is faulty. Pumps can’t be repaired, they are replaced. And we cover that below.

Visually check pump flow

For this test, we’ll need an empty water bottle, length of fuel line, and an appropriate small pick to remove the fuel line from the fuel pump. The pump wiring will need to be connected.

The process is as follows:

• Remove the fuel line from the pump
• Fit length of fuel line to fuel pump and feed into a water bottle
• Activate the pump (ignition switch position 2)

No fuel flow or a weak flow means the pump needs to be replaced.

A solid flow means it appears the pump is good, that said manufacturers do have a min quantity flow over a given time.

Use fuel pressure gauge to test system pressure

For this test, we’ll need a fuel pressure test kit. Your manufacturer will specify a min fuel pressure and head pressure specs for the pump.

I look for the pressure to be maintained with key on and then when running check the min spec is being maintained when the engine is loaded. Somewhere between 40 to 60 psi is typical.

The process is as follows:

• Connect fuel pressure gauge

• First check key on fuel pressure.
• Now check min pressure with the engine running.

If the pump fails this test, go ahead and replace it.

How To Change ATV Electric Fuel Pump

To fit a fuel pump we’ll need mostly regular hand tools but some models may require a special fuel pump release tool, but a good set of channel locks does the job too.

The process is as follows:

• Remove fuel line
• Remove pump wiring terminal
• Clean the area around the pump
• Mark the location of the keeper (lets you know how much to tighten later)
• Using channel locks loosen and remove the keeper
• Remove pump and sender unit

The pump and sender unit are usually removed as one unit, meaning we’ll need to remove the pump from the assembly.

The process is as follows:

• Move to a workbench and remove the filter mesh from the pump
• Remove the pump push-on wire terminals (take a pic first if needed)
• Remove fuel line
• Remove pump from sending unit

Refitting is the reverse. However, some new pump kits may include pump O-ring seals and fuel line length and clips. It depends on the pump type fitted.

Pump fitting tips:

• Use non-petroleum lube on rubber seals to help fitting and sealing (silicone grease)
• Use dielectric grease on electrical terminals helps prevent moisture
• Tighten pump keeper to your mark
• Check for leaks after rebuild

How to Diagnose ATV Mechanical Fuel Pump

The mechanical fuel pump is a lot easier to locate, test, and work on. The pump is usually small and located close to the gas tank. Following the fuel line from the gas tank will help you locate the pump.

It will employ a fuel line in (from the gas tank) and a fuel line out (to the carburetor) and a pulsing hose that’s connected to the engine crankcase breather system.

Some checks we can run before removing any components include:

• Check that we have sufficient fuel inside the gas tank
• Check the gas tap is turned fully on
• Check the vacuum hose to the pump (a split, perished or otherwise damaged hose will prevent the pulsing vacuum needed to power the pumping action)

With these simple checks out of the way, we can now begin to diagnose. The steps are as follows:

• Remove the carburetor fuel line and place the open end into a suitable clear container (an empty water bottle works great)
• Have helper crank over the motor
• Check fuel flow to the container

A good pump will pulse a plenty feed of fuel

A bad pump will supply no fuel or poor fuel flow

Replacing a mechanical is an easy task requiring only basic tools. But do check that vacuum line, it is critical to fuel pump operation. Replace fuel line clamps and check for leaks on completion.

You may also find the following posts helpful:

ATV troubleshooting

ATV flooded with gas

ATV won’t start after wash

ATV won’t pull start

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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The post How to Tell ATV Fuel Pump is Bad? This is how … appeared first on ATVFixed.com.

A flat battery is a common everyday issue and easy to solve, you jumpstart her, right? But what do you do if even jumpstarting doesn’t solve the problem? Well, you are in the right place, I’m a mechanic and very shortly we’ll have it figured out.

Four common reasons an ATV won’t jumpstart, include:

1. Loose battery terminals
2. Wrong jumpstarting sequence
3. Faulty starter solenoid
4. Faulty neutral switch

In this post, we’ll cover all the common reasons your ATV won’t start, how to diagnose them and what you can do to fix them right now!

Pre Diagnosis Checks

Before we get into the actual diagnosis of the no start let’s first check we’re on the same page. To do that we’ll need to know what noise your engine makes when you attempt to jumpstart. The answer to this question will help determine what the likely cause is and therefore help get you back rolling quickly.

When jumpstarting and you hit the start button, commonly you’ll hear one of four sounds. Check out the links below that corresponds with what sound your ATV makes (if any) when you hit the start button.

The four likely sounds are:

1. Repeated clicking sound
2. Single click sound
3. No sound at all
4. The engine just cranks over, but doesn’t start (this is a biggie and I’ve covered it previously. You can check that out here – ATV won’t start)

Loose/Dirty ATV Battery Terminals

I’ve put this at the top of our list because it’s common and a one-minute fix, you’ll likely spend longer looking for the wrench than fixing the problem.

ATVs bounce about a lot and so it’s no surprise a few fasteners come loose from time to time. Of course, we should check the battery terminal fasteners are tight during maintenance checks, but given their location, they’re forgotten.

Anyhow, loose terminals create resistance to the flow of voltage both from the battery but also to the battery meaning your battery power can’t get to the starter motor, and nor can the charging system get voltage to the battery.

Diagnose: Access the battery and move the terminals from side to side, if they move they will create high resistance.

Fix: Use an adjustable wrench to snug them up, but not too tight, these guys can break if over tightened.

Dirty Battery Terminals

Dirty terminals will also cause resistance issues and is another common cause of hard starting. Corrosion can be seen as a white crusty buildup on the terminal itself. This is acid and will burn the skin, so use caution.

Diagnose White crusty buildup on the battery terminals.

Fix: Clean terminals but first neutralize the acid by mixing baking soda and some water into a paste and applying to the corrosion. After a few minutes, you are free to remove the terminal, clean it with sandpaper or wire brush snd refit, taking to tighten it securely.

Apply some petroleum jelly to help guard against future corrosion.

Wrong ATV Jumpstarting Sequence

Jumpstarting isn’t difficult, but sometimes when attempting to jumpstart in difficult conditions, terrain, or maybe in poor light, cables can get mixed up. Best to take a moment to check that the jumper cables are connected correctly.

Connect the cables in the following order:

1. ATV battery Positive (+)
2. Donor battery Positive (+)
3. Donor battery negative (-)
4. Ground point

You may use any 12-volt battery, or donor vehicle such as Car, Truck, Tractor mower, RV, etc. I’ve covered jumpstarting an ATV previously in greater detail and you can check that post out right here – How to jumpstart an ATV in 6 easy steps

A very common root cause of unsuccessful jumpstarting is not the fitting sequence but the cables themselves. Yep, bad quality or faulty cables are a pain because they lead you to believe you have a different problem. I’ve been caught once burning time because of faulty cables.

Anyhow make sure your cables are up to the job, weak crocodile clamps or frayed wires at the clamps are where they usually fail. I’ve listed a good-quality jumper set and a jump pack on the ATV tools page here.

Faulty ATV Starter Solenoid

The starter solenoid is a relay, it connects the battery to the starter motor when but only when the relay is activated by the start button. Solenoids work hard and fail regularly, a common tell-tale symptom is a single click sound when the water button is pressed.

That said a single click sound may be caused by some faults too low battery (although more often, a low battery offers several repeated clicks); valve lash out of spec; hydro locked engine; engine failure.

We’ll eliminate all of these as possibilities by checking the solenoid starter solenoid. After all it is the most likely reason we hear the departed clicking sound. However, if our solenoid tests is good, you’ll need to visit all these other possibilities just mentioned.

Testing the starter solenoid

To test the starter solenoid we’ll need two lengths of electrical wire one fuesed. In this test we’ll bypass the start switch and the ignition switch. The bike should be in neutral and parking brake applied, we’ll be cranking over the engine and if it’s in gear it will move. Testa as follows:

First locate the starter solenoid, usually close to the battery.

Access the two light gauge wires and remove them.

Using two jumper wires, (power fused) attach one to the positive battery and the other to the negative (as per picture).

Two outcomes are possible:

Your engine doesn’t crank over, it just clicks once. Most likely your starter solenoid has failed, as said they fail regurarly, and I’d just go ahead and replace it. That said there are a couple of other possible causes (less likely) and in the interest of a complete diagnosis you can check those out here in this post – ATV will only pull start

Engine crank over as normal – That’s great! But it means you’ll need to check out your safety lock-out system (neutral switch clutch switch etc,) or kill switch. Check out – ATV will only pull start, it covers the subject in more detail.

Faulty ATV Neutral Switch

A common cause of no sound at all when the start button is pressed is the Kill switch, worth taking a moment to check it’s in the RUN position. Hey, it happens.

However, for most, the more likely issue is a more technical issue such as a faulty lock-out system wiring or sensor issue. A transmission neutral switch is the most common sensor or switch used to prevent unintended in gear starts, but some may use a clutch lever too.

As you know the neutral light must be on in order for the starter to engage. If your light isn’t lit your bike’s CDI or ECU assumes the bike is in gear and won’t send power to the starter motor.

While obviously starting circuits vary from maker to maker but even the simplest ATV wiring circuits will incorporate a safety lock-out feature or maybe two.

I wrote an article on checking neutral light issues and you can check it out here – Neutral light always on

Other Possible Causes

Here you’ll find some other less likely but still possible causes of a no crank when attempting a jumpstart.

• Faulty starter motor – ATV will only pull start
• Hydro locked engine – ATV won’t start
• Engine flooded – ATV flooded with gas
• Faulty CDI/ECU
• Wiring issue
• Mechanical fault – ATV has spark and fuel but won’t start

You may also like the following posts:

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How to tell if ATV fuel pump is bad

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ATV has spark and fuel but won’t start

How often should I service ATV?

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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The post ATV Won’t Jump Start – This will fix it appeared first on ATVFixed.com.

A flat battery is a royal pain in the ass and there’s never a good time to have one, that said as problems go it’s a simple fix. I’m a mechanic, you are in the right place and very shortly we’ll have this figured out.

To jumpstart an ATV you’ll need a donor battery and a set of jumper cables. Connect the cables in the following sequence:

1. Positive on ATV
2. Positive on Donor
3. Negative on donor
4. Ground on ATV
5. Start engine

In this post, you’ll learn how to jump-start your ATV quickly and safely. You’ll also learn how to charge your battery, how to check your battery health, and how to check your alternator output, let’s get to it.

Jumpstarting ATV Procedure

Jumpstarting an ATV is a simple procedure every rider should know. The procedure is not without risk, batteries contain acid and vent flammable vapors. Arcing a jumper cable is enough to cause the vapors to ignite. While this is a small risk, it is possible if you fail to follow the set jumpstarting sequence set out below.

In addition, connecting the jumper cables incorrectly can damage both the donor vehicle/battery and your ATV’s electrical system, so it’s important to get this correct.

Tools we’ll need:

Donor vehicle/battery – Obviously we’ll need a donor vehicle or battery. Most vehicles run the same voltage system as your ATV, it’s known as a 12-volt system (although these systems are actually 12.65 volts). This is great news as it means we have a wide choice of vehicles we can use as a donor vehicle.

Cars, including hybrids and even EVs, are suitable as they run a 12-volt system alongside their higher voltage drive systems. Trucks, RVs, Riding mowers, and Dirt bikes, all use 12 volt systems and are perfect for a jumpstart.

To check your donor vehicle is a 12-volt system, go ahead and locate the battery and check the battery casing label, it will clearly state – 12 volt

There’s is also the option of using a jumper pack instead of a donor vehicle to boost start your ATV and we’ll cover that procedure below also.

Jumper cables – A good quality set of jumpers are important, poor quality jumpers will create resistance to the flow of power between batteries. Cheap cables are pain and in my opinion a waste of money. Cheap cables typically use cheap narrow gauge wire and poor clamps which as said make poor connections. Check out the ATV tools page to see the jumper set I recommend.

The process of jumpstarting is as follows:

• Access your ATV battery (usually under the seat)
• Check both battery terminals are clean and tight
• Park your donor vehicle close to your ATV
• Access the battery and identify the battery poles (embossed on the battery casing and/or terminal cover).

• The Positive terminal is marked by a PLUS symbol (+) and maybe color-coded RED. The Negative terminal is marked by a Minus symbol (-) and color-coded BLACK

The positive terminal connects to the fuse box and the negative terminal connects to chassis ground (Grd)

Connect the cables as follows:

1. ATV battery Positive (+)
2. Donor battery Positive (+)
3. Donor battery negative (-)
4. Ground point

A ground point (Grd) is any metal on the chassis or engine. We use the ground point instead of the negative terminal of the ATV battery as the final cable often causes a small arc (spark). The arc as said could potentially ignite battery vapors if connected close to the battery vent.

Starting your ATV

With all cables connected, go ahead and start your ATV and allow the engine to idle as normal. Avoid revving while jumper cables are connected.

A repeated clicking sound as you hit the start button means the batteries aren’t making a good connection, readjust them and try again.

If your ATV fails to start and offers a single click sound, you likely have a failed solenoid and not a flat battery, I wrote a post previously that covers starter solenoid testing and you can check it out here – ATV won’t start

Removing the jumper cables

While your ATV is idling, remove the jumper cables in reverse order to how we fitted them.

Remove 4, 3, 2, and 1.

If your battery is generally healthy, and your charging system is in good shape simply riding your bike for thirty minutes or so without using electrical consumers such as lights, etc, is enough to charge the battery.

However, if you have a weak battery, bad alternator, or parasitic drain you’ll be visiting this problem again before long. Makes sense to test your battery and charging system to make sure all is in order, and we cover exactly that below, but first I’ll cover boost starting your ATV using a jump pack.

How to Boost Start ATV with Jump Pack

Boost starting from a jump pack is similar to the jumpstarting process only a ton easier. A jump pack is a really useful tool to have, modern jump packs are small enough to fit in the glove box of a car and yet powerful enough to start a diesel truck, these little guys pack. Check out the ATV tools page to see the jump pack I recommend.

The jump pack process is as follows:

• Connect the Red Jump pack clamp to battery Positive (+)
• Connect black jump pack clamp to battery Negative (-)
• Start engine

Jump packs employ an anti arc feature which prevents the risk of igniting battery vapors, however, as an alternative you can connect a jump pack black clamp to a chassis or engine ground also.

How to Check ATV Battery Health

Checking your battery’s state of health is a two-step process. First, we’ll need to check battery voltage and then we stress the battery by running the Crank test. We run a voltage test first to check the state of battery charge because running the crank test on a partially charged battery will lead to misdiagnosis.

The tool you’ll need:

In this test, I use a voltmeter (DVOM) but you can also use a dedicated battery tester which is also capable of running a charging system test (covered below). The battery tester uses a traffic light system and is easy to use, the voltmeter is a little more work, anyhow you’ll find both tools here on the ATV tools page.

Check Battery Voltage – Let’s go ahead and check battery voltage using our voltmeter as follows:

• Place the red meter probe on battery Positive (+)
• Place the black meter probe on battery Negative (-)
• Read meter

Crank test – A battery may display full voltage (12.65 v), but that doesn’t mean the battery is good. When stressed it could fail and as you know that’s why we run the Crank test.

If your battery isn’t at least 12.5 volts, go ahead and charge it before running the crank test. To charge it you can run the engine or use a battery charger.

• Place the red meter probe on battery Positive (+)
• Place the black meter probe on battery Negative (-)
• Crank over the engine
• Read meter

What the results mean

A reading below 9.6 volts indicates a weak battery

Reading above 9.6 volts indicates the battery is good

How to Charge ATV Battery

Batteries don’t like sitting idle, they are designed to be used, charged, and discharged continuously. That’s what keeps a battery vibrant. And that’s why I recommend using a smart battery charger also known as a trickle charger when your bike is laying up for more than a week.

The smart charger is designed to monitor your battery state of charge and turn on and off as needed. Check out the ATV tools page to see the smart charger I recommend.

If your battery state of charge is very low your charger may not turn on, this is a safety feature.

To override this connect a donor battery and then connect the career as per the picture. The donor battery may be removed after 30 mins and continue to charge as required.

To charge your battery, follow these steps:

• Remove the negative terminal (helps remove any risk of electrical system damage caused by voltage spikes)
• Check the battery terminals are clean
• Attach the red battery clamp to battery positive (+)
• Attach the black battery clamp to battery Negative (-)
• Set charger to 12 volts, plug in and turn on

Charge time will depend on how low your ATV battery is, its amp rating, and the amp rating of the charger. Typically 3-4 hours.

How to Check ATV Alternator Output

This is a simple check and to nail it like a pro you’ll need either a Voltmeter or a battery/alternator tool and a helper would be useful. You’ll find both these tools on the ATV tools page here, but not the helper.

First, we’ll need to access the battery, then follow these steps:

• Start the bike and allow it idle (helper)
• Set the voltmeter to 20 v DC
• Place red meter probe on battery positive (+)
• Place the black probe on battery negative (-)
• Take the revs up to about 3000rpm (helper)
• Check the meter reading

What the results mean

A reading below 12.65 volts indicates your charging system isn’t working, further investigation is needed. Possible faulty stator, rectifier/regulator, or wiring circuit.

A reading above 13 volts and below 15.5 volts indicates your charging system is charging and working as it should.

A reading above 15.5 volts indicates your rectifier/regulator is faulty

If you suspect an intermittent charging issue, repeat the test with lights, etc turned on. A healthy system will offer the same results as per the previous test.

Common Causes of ATV Flat Battery

A flat battery happens to us all, sometimes it’s operator error and if that’s the reason you have a flat battery, consider yourself lucky, your work is done here, if not we may need to do a little detective work.

The most common reason for a flat battery is battery failure and we’ve covered battery testing above.

Other causes include the following:

Loose battery terminals – ATVs bounce about a lot, it’s not uncommon for battery terminals to come loose. Loose terminals will create resistance (obstruction to the flow of power), it stops battery power from getting to the starter motor but the reverse is true also, the charging states can’t get full voltage to the battery.

Dirty battery terminals – Leaking acid and arcing can cause a build-up of corrosion on the terminal which results in high resistance with the same results as a loose battery terminal.

A faulty rectifier/regulator – The rectifier regulator is a critical charging system component. It takes alternating voltage (AC) produced by the stator and converts it into direct current (DC) used by your ATV.

In addition, the regulator monitors and adjusts battery charging voltage which is critical for a healthy battery. A faulty rectifier/regulator commonly causes premature battery failure as it overcharges the battery.

In addition, a neglected faulty rectifier/regulator may damage the CDI box, which results in an ignition system failure and a no-start.

Short to ground – A short is common in older more experienced ATVs, loose or trapped wiring shorts off the ground (chassis or engine metal frame). The short causes a constant drain on the system.

Accessories are a common source of electrical shorts since the wiring isn’t factory fitted they tend to come to loose more often.

Failed Stator – The battery is responsible as you know for starting the engine but the stator generates all the voltage needed to run the bike and replace spent battery voltage. A faulty stator will affect battery charging and may in some cases drain the battery.

You may also find the following posts helpful

ATV troubleshooting

ATV lights not working

ATV has spark and fuel but won’t start

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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The post How do You Jump Start an ATV? In 6 easy steps appeared first on ATVFixed.com.

There’s never a good time to break down but not to worry, I’m a mechanic, and very shortly we’ll have this figured out.

6 Common reasons an ATV won’t start, include:

1. Flat battery – jump or charge battery
2. Loose battery terminals – tighten terminals
3. Fouled spark plug – clean or replace plug
4. Flooded engine – dry out cylinder
5. Stale gas – drain and refill
6. Faulty starter solenoid – test & replace

In this post, you’ll learn how to fault find your no-start ATV like a pro. We’ll cover diagnosis and you’ll learn some insider tips and hacks to speed up the process of both diagnosis and repair.

Mechanics advise for fault finding ATV

A mechanic/technician uses two main strategies when fault finding. We typically use the Common causes approach and the top-down approach.

Now it should be noted, that many latest bikes store fault codes in their ECU (on-board computer) and if your bike is fuel-injected and if a problem is flagged by the ECU, that fault code will be stored and is accessible. Reading these fault codes is obviously a great place to start your diagnosis.

As each manufacturer has a slightly different method for reading and interpreting their fault codes, it is best to google your make and model first. Typically, connecting a fault code harness wire causes the ECU to communicate the codes by flashing dash lights a number of times.

All that said you can still use this article to fault find both carburetor and fuel injected bikes without reading the fault codes.

1 Common Causes Approach

The common causes approach is self-explanatory. Most technicians look at the symptoms of a problem ATV and using their experience (in our case – common ATV no-start causes) set about testing their hypothesis.

Most often, checking the common causes yields success and for obvious reasons, but every so often you’ll meet an exception, you’ll exhaust all the common causes with no luck and so the diagnosis must take our second approach, the top-down approach.

2 Top-Down Approach

A top-down approach is a systematic approach to fault finding. A technician still reads symptoms to direct their firepower but thereafter begins the test and evaluation process until the fault yields.

This type of fault-finding is hard work and often time-consuming and that’s why we’ll look at the common causes approach first before moving to test from the top down.

So let’s go ahead and start by checking those common causes right now.

1 Common No Start ATV Causes

Common causes obviously vary by make and model. Many ATVs, for example, employ auto choke, and most late models are fuel injected and so eliminate a ton of common faults associated with carburetor models, but at the same time, open up new common cause territories.

There is some overlap between the carburetor and fuel-injected bikes, but as their fueling system are different, we’ll deal with those systems separately. Remember, the list below isn’t a complete list of no start causes, just the common ones. We deal with a more complete list later in the second approach.

Common No-start ATV causes, symptoms & fix (carburetor & fuel injected)

Common (fuel injected) No-start ATV causes, symptoms & fix

Common (carburetor) No-start ATV causes, symptoms & fix

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2 Top-Down ATV Troubleshooting

If the common causes didn’t work out for you, not to worry the top-down approach and some patience will force a submission. We’ll need a few test tools along the way, but I’ll let you know what they are and, of course, how to use them.

Check a fact is a fact

As a technician, I’ve worked for GM, VW, Landrover, Jaguar, and Volvo dealers, and all their dealer product training employs a very similar concept. When presented with a reported problem – page one, step one – “Check the reported problem is in fact a problem”

In many cases, the error isn’t with the machine, it’s the operator, and so in the next section, we’ll quickly check that all those facts are in fact, facts.

Easy fix No-Start ATV Causes

Let’s start by looking at some of the easy-to-fix causes of ATV no-starts. In many cases, as said, a small oversight by the operator is the root cause. I know you know how to start your ATV; you’ve likely started it hundreds of times. But this step won’t take but a moment, and then we can move on and do some proper diagnosis, promise!

Okay, let’s quickly eliminate some common operator errors as root causes of our no-start.

Check the following:

Gas level – Gas in the tank is obviously crucial; running out of gas is common and has caught us all out. Yes, even mechanics!

Kill switch – The kill switch, as you know, shuts down the motor. The switch must be set to “Run” in order for the engine to restart.

Check your kill switch is set to “Run”.

Choke use – A choke adds extra gas and is required to start a cold engine. Some ATVs employ a manual control and if that’s yours, it will need to be set to the “ON” position.

Many modern bikes employ auto choke, and if your bike is fuel injected, (lucky you), cold start fueling is automatic; it’s controlled by the onboard computer, and no action is required.

Correct starting procedure – ATVs, as you know, employ a safety lockout procedure, meaning if you don’t follow a set starting procedure, the engine won’t crank over or start.

Typically, the bike transmission needs to be in neutral; some will require a clutch held and some the brake applied.

Check your make, and model starting procedure online.

Gas tap “On” – The gas tap is also known as Petcock or Gas valve. Most bikes are fitted with a gas tap, when in use it prevents gas flow from the tank to the engine. Commonly the tap is turned off when a bike is parked up.

Check Petcock is set to “On”.

OK, that’s the low-hanging fruit out of the way, now let’s do a little detective work.

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ATV No-start Pre-diagnosis Detective Work

I’ve been a mechanic for over twenty-five years, and I’ve found when fault finding you can learn a ton and get a head start on fixing the problem without even looking at the machine.

Simply taking a few moments to listen to the customer explain the issue and asking a few probing questions often sets us on the correct path.

The main question to consider is – What were the factors at play prior to the engine stalling out or not restarting? (whichever is applicable)

For example:

• Did you just refuel? – gas could be stale or contaminated
• Bike won’t start when hot? – engine could be flooded by excessive choke use
• Bike won’t start when cold? – choke or temperature sensor (fuel injected bikes) may be at fault
• Did you drive through water? – the electrics could be wet
• Has the bike been laid up for a time (month plus)? – gas tap may be off or the fuel may be stale
• Have you added mods, like exhausts, free flow air filter or wired accessories, etc.? – some performance mods will require carburetor fuel adjustment
• Have you been working on the engine when it quit? – carburetor tuning, engine timing, and valve lash are all common no start causes after engine repairs/adjustments/modifications

Having spent a few moments considering the above, we’ll assume for now it wasn’t fruitful, and so we’ll move to the next phase where we’ll attempt to broadly identify and label the root cause of your ATV no-start.

What do you Hear when you Hit ATV Start Button?

When diagnosing, I find it helpful to broadly categorize symptoms and assign them to labeled buckets, metaphorically speaking.

Within these buckets, I’ll make a list of the various components that are a likely root cause of that buckets symptom (label).

Thinking in these terms helps to exclude a broad range of issues and conversely causes us to focus on a narrower more likely range of possible causes.

Each bucket, as said will contain the most likely components to cause issues and we’ll look at all these in more detail a little later. But for now, let’s go ahead and categorize your ATV starting symptom so that it fits neatly into one of our five buckets.

And to do that successfully, we’ll need to pay particular attention to what noise your ATV makes when we attempt to start the engine, ie crank the engine over. For those that aren’t familiar with the term “crank engine over” – it describes the cycling (also known as turning over) of the engine as the start button is pressed.

Go ahead and categorize your symptom, assign it to one of the following buckets and begin diagnosing.

Your engine makes one of the following noises when the start button is pressed:

• Bucket 1 – Engine makes a REPEATED clicking sound
• Bucket 2 – Engine makes a SINGLE click sound
• Bucket 3 – Engine cranks over but sounds SLOW
• Bucket 4 – Engine makes NO sound at all
• Bucket 5 – Engine cranks over, it sounds NORMAL, but won’t start

Bucket 1 – ATV Engine makes a REPEATED clicking sound

If your engine makes a repeated clicking sound when you hit the start button, then consider yourself lucky.

This type of issue is common and is by far one of the easiest faults to diagnose and fix.

The most likely issue is a flat battery, but wow there! Let’s now jump to conclusions, there are some other possibilities, but all the fixes for this symptom are easy, and frankly, I’m jealous!

Faults are listed below in order of how likely they are. Follow each highlighted link, in turn, to diagnose and eliminate it from the list of possible issues, rinse and repeat until you nail it.

Battery Terminals Loose

Loose terminals are common and really easy to diagnose and fix.

Diagnose – Access the battery (usually under the seat) and wiggle the terminals.

Tools: Adjustable wrench

Fix – If they are loose, tighten them – problem solved.

Battery Terminals dirty

Dirty terminals are another really common issue and almost as easy to fix as loose battery terminals.

An acid weep from the battery combined with arcing causes battery terminal corrosion.

And corrosion causes resistance to the flow of power from the battery to the starter motor. The dirty terminals conversely prevent alternator voltage recharging the battery.

Diagnose – It’s easy to spot, it forms a white crusty deposit on the terminal.

Tools:

• Disposable gloves
• Eye protection
• Baking soda and water
• Rag
• Small adjustable wrench
• Sandpaper or wire brush
• Petroleum jelly

Fix – The fix is simple, remove the corrosion. But wow, not so fast, acid will burn the skin and eyes, we’ll need to neutralize it first.

The whole process is as follows:

• Add a tablespoon of baking soda to some water and work into a paste.
• Using an old cloth and gloves or brush add the paste to the terminal
• Allow a few minutes for the paste to work its magic before wiping clean
• Remove battery terminals (need a wrench)
• Using sandpaper or a wire brush clean the terminals
• Refit the terminals and tighten
• Add a coat of petroleum jelly to terminals (prevents corrosion)

Battery Flat

We’ve all suffered a flat battery at some point in time. Sometimes it’s all on us (leaving the ignition switch on), but more commonly, it’s because either the battery hasn’t been maintained correctly or the battery is in the early stages of complete failure.

Either way, we’ll need to check the voltage and charge the battery back up. A flat battery obviously won’t start your engine, but we can’t test a flat battery either.

Tools:

• To test the battery we’ll need a DVOM (voltmeter)
• To charge the battery we’ll need a battery charger
• If you wish to boost start we’ll need a jump pack or jumper cables

You’ll find all these tools here on the ATV tools page.

Diagnose – A repeated clicking sound from the engine is a pretty good indication we have a battery issue. Of course, no sound at all is another symptom of a totally flat battery. To confirm this, even without breaking out a voltmeter, you could turn the lights on full; if they are dim, you can be sure your battery charge is low.

Next, we’ll use a voltmeter to confirm this; however, if you just want to get rolling, you can jump ahead to battery charging or, for immediate results jumpstarting.

Checking ATV battery voltage with DVOM (voltmeter) as follows:

• Set meter to 20 DC
• Red probe on + battery terminal
• Black probe on – battery terminal
• Read meter

A voltage reading below 12.4 volts may struggle to start your engine, especially in cold weather. Batteries don’t like laying idle either, they much prefer being used ie discharged, and recharged, it keeps them vibrant.

If you park your ATV up for weeks on end, I’d advise using a battery maintainer, also known as a smart charger. Fit them to the battery plug them in and forget them. They turn on and off automatically and use little energy. A good charger will save you money in the longer game. You can check out the smart charger I use here on the ATV tools page.

Fix: The fastest way to get rolling again is jumpstarting. Starting the vehicle will use your ATVs alternator to charge the battery. But you should note, if the battery is faulty or the charging system is at the root cause of the flat battery you’ll be visiting this problem again. After charging the battery it’s best to have it tested, and we cover that below.

To jumpstart you will require a donor vehicle, it doesn’t need to be another ATV, any 12-volt vehicle will work. A car, truck, motorbike, tractor mower, RV, etc all run a regular 12-volt system.

If in doubt check the battery casing where it states the battery voltage. (12 volt systems are referred to as 12 volts but actually are 12.65 volts).

Jumpstarting

The jumpstart process is as follows:

Connect cables as per diagram:

• Connect 1,2,3 and 4
• Start engine
• Remove 4,3,2 and 1

Don’t want to jumpstart, Ok our second option is to charge the battery. Obviously, we’ll need a battery charger for this fix. Note – Many battery chargers employ a fail-safe system that won’t allow the charger to turn on if battery volts are too low.

You can check out the charger I recommend here on the ATV tools page.

Battery Charging

Connect a battery charger as follows:

• Connect red to battery +
• Connect black to battery –
• Plug in charger
• Charge for 3-4 hours (depending on battery state of charge and charger Amp rating)

To override this connect a spare battery to turn the charger on, the donor may be removed after 30 minutes and continue to charge for approximately a further 3-4 hours.

Battery Faulty

Batteries wear out and die, even well-maintained batteries eventually give up. batteries typically last 4 to 6 years, sure some batteries last longer but they tend to be the exceptions.

Tools:

• We’ll need a DVOM (voltmeter) to test the battery
• We’ll need an adjustable wrench to swap out the battery

Diagnose: Diagnosing a battery isn’t difficult. It is a two-step process. We first establish the state of charge before running the step two crank test. We check the voltage (step one), first because unless the battery is charged to at least 12.5 volts, step two will not give a true state of battery health.

In this test, I use a DVOM, and a helper to read battery voltage. It’s not difficult, but it is laborious when compared to a battery test tool designed for the job. And so if you prefer to use a battery tester, I have listed an easy-to-use plug-and-play type battery tester that uses a simple traffic light system to test your battery.

You can check out the battery tester I recommend here on the ATV tools page.

Crank test is as follows:

• Set meter to 20v DC
• Set to MIN/Max
• Red probe to battery +
• Black probe to battery –
• Helper cranks motor over

A reading below 9.6v indicates a failing battery.

Fix: Replace the battery

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Back to Bucket 1

Bucket 2 – ATV Engine makes a SINGLE click sound

A single-click sound from the engine when you hit the start button is a common sound to many an ATV rider. It’s the sound of a faulty starter solenoid.

As problems go, a faulty solenoid is an easy fix, but just before we make the mistake of misdiagnosis let’s first test it and if it checks out OK, run the other tests in this list.

Faults are listed below in order of how likely they are. Follow each highlighted link, in turn, to diagnose and eliminate it from the list of possible issues, rinse and repeat until you nail it.

Starter Solenoid

A failed starter solenoid is a very common cause of a single-click sound. The solenoid is a relay and as you know they are responsible for sending power to the starter motor. Solenoids just wear out. In truth, some of the places solenoids are positioned invite trouble. Some models place them under the fender and surprise surprise they fail regularly.

Anyhow I covered testing the solenoid in greater detail previously right here – ATV will only pull start

You may find this post helpful also – ATV click no start

Hydro-locked Engine

A hydro-locked engine isn’t common but it can happen under certain circumstances. Hydro-locking is where the cylinder fills with fluid and since the fluid isn’t compressible the piston can’t move inside the cylinder.

How did the fluid get in there? Driving into the drink is one possibility, so too is a leaking carburetor float valve or a failed head gasket that allows coolant enters the cylinder.

Removing the spark plug releases the fluid, but it doesn’t fix the root cause.

I’ve covered Hydro-locking in greater detail previously, together with some other causes of an engine that’s stiff or refuses to turn over.

You can check it out right here – ATV won’t pull start

Check out – Can ATV go in the water?

Engine Restriction

A restricted crankshaft, piston, or valvetrain will prevent the engine from cranking over. And by restriction here, I’m thinking of a major mechanical failure.

The result is a single click sound when the start button is pressed, that sound is the solenoid doing its job, but the starter doesn’t follow up by rotating the engine.

We need to find out why.

Tools: Good socket and ratchet set including a plug socket and breaker bar

Diagnose:

• Remove spark plug
• Remove the engine side cover to access the crank fastener

• If your ATV has a pull starter you won’t need to remove the pull assembly
• Using the breaker bar & socket, attempt to rotate the engine slowly CCW or for pull starter, attempt to pull over the engine slowly with pull starter.

If the engine is locked tight, suspect engine damage, but before assuming the worst, best to remove the starter motor and repeat the test. A starter motor issue is still possible and starter motor testing is covered below in greater detail.

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Back to Bucket 2

Bucket 3 – ATV Engine cranks over but sounds SLOW

This is a very common symptom associated with a no-start especially in colder weather and after an ATV has been sitting idle for a time.

The usual root cause is a battery that is low on voltage, a jumpstart from any 12-volt vehicle is the fast fix but you could also charge the battery using a battery charger.

And although this is the most likely of the slow crank, it isn’t the only possible explanation, you’ll find the other in the list below.

Faults are listed below in order of how likely they are. Follow each highlighted link, in turn, to diagnose and eliminate it from the list of possible issues, rinse and repeat until you nail it.

Oil Level Overfull

An engine is designed to hold a set amount of oil, too much oil can cause problems. An engine requires a void inside the crankcase to deal with negative and positive crankcase pressure caused by the moving crankshaft, piston, and valvetrain.

Overfilling with oil then fills this critical void and causes other issues, a slow or no crank is among them.

Diagnose: Go ahead and check your oil level.

Fix: Remove excess oil

Oil Type

Oil type is important and we should always use the oil specified by the engine maker. That said if your ATV lives and works in extreme conditions you may need to move to a more suitable grade.

In colder temps, a heavier oil grade moves like treacle, and that can as you know cause engine damage, but also a slow crank speed and a no start.

Fix: Move to a lighter oil grade

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Back to Bucket 3

Bucket 4 – ATV Engine makes NO SOUND at all

This symptom has the potential to be a super easy fix or a troublesome one. I know that’s not the most helpful information but stick with me here and you’ll see what I mean.

Faults are listed below in order of how likely they are. Follow each highlighted link, in turn, to diagnose and eliminate it from the list of possible issues, rinse and repeat until you nail it.

Main Fuse Blown

The main fuse is so-called because it’s the parent fuse, meaning all circuit power passes through it.

If the main fuse is blown, power won’t flow.

Diagnosis: The main fuse is located close to the battery under the seat. Remove the fuse and check the element. Fuses commonly blow because there’s a short in the circuit, other reasons include incorrect fuse size (too small), failed component, or just an overloaded circuit (accessories drawing excessive amps).

Fix: If the fuse is blown replace it, be sure to use the correct fuse amp rating.

Kill Switch Issue

With the kill switch set to stop, power flow to the starter motor is blocked, and if the kill switch fails to engage in the run position, many ATVs will offer the no sound at all symptom when the start button is pressed.

As not all kill switches are wired the same, a wiring diagram would be useful. That said kill switches either open a circuit or close a circuit. So when testing, just make sure the DVOM reading changes when the switch is operated.

Tools: DVOM

Diagnose: Disconnect the switch block connector and check continuity. (Never test continuity on a live circuit)

Fix: Repair or replace the switch

Wiring Issue

Circuit wiring issues are common in older ATVs and the best way to approach a wiring issue is with a wiring diagram and a power probe. Check out the power probe I recommend here on the ATV tools page.

As power must move in a circle, using a power probe begin by checking the power side of the circuit, (fuses, etc) then move to check the ground side of the circuit.

Broken, loose, and corroded wiring or terminals are very common types of electrical issues. So too is rodent damage, mice love wiring insulation.

Neutral Switch

A neutral switch is a switch located on the transmission and is used by the CDI/ECU to identify when the transmission is in neutral. ATVs employ a safety lock-out procedure to prevent accidental in-gear starting.

The neutral switch plays a critical role, meaning if the neutral switch isn’t working the ECU/CDI may not permit starter motor activation.

Diagnose: Check if neutral light is on the dash panel when ATV is in neutral. I’ve covered neutral switch diagnosis previously and you can check that out here – Neutral light always on

Fix: Test and replace the neutral switch.

CDI Box Fault

CDIs and ECUs are difficult to diagnose. Most technicians will call them bad only after first exhausting all other possibilities. What we can check is power and ground to the modules and we can check the block terminal connector for loose block connectors, water, corrosion, or pin damage.

It should be noted, that a failed Rectifier/regulator will not only fry your battery but is also a common cause of CDI failure. If your ATV is overcharging the battery (over 15.5v) replace the rectifier/regulator.

CDIs and ECUs are pretty durable and are last on this list for good reason.

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Back to Bucket 4

Bucket 5 – ATV Engine cranks over, it sounds NORMAL, but won’t start

The list of possible no-start causes in this bucket is too large to list, and so in order to make it more manageable, this bucket contains 3 subcategories.

These categories, which we’ll call systems don’t contain a list of faults as per previous buckets, instead they contain a list of components.

The 3 systems are categorized as follows:

• (I) Ignition system
• (II) Fueling system
• (III) Compression system

We use just 3 categories because an engine needs these 3 main systems to work in harmony in order for the magic to happen. If one of these systems isn’t working, you’ve guessed it, you get a no-start.

As said each system contains a ton of components on which that system relies. Below, I’ve listed the main components under each system heading. One of these components within one of the 3 systems has failed and is causing our no-start.

I know the list below is long, but don’t be disheartened, I have a secret mechanics hack to short circuit the diagnosis process, meaning you won’t need to check all 3 systems or indeed all the components within the systems. So let’s check out that hack right now.

Gas Shot Test

The gas shot test is an elimination round and answers many questions very quickly. I use this hack in the workshop all the time. The idea is simple, the results of this test will indicate which of our 3 systems has likely failed. It won’t point to the failed component within that system, we’ll still need to do some detective work. But we will at least be searching in the correct category if you like.

Gas shot test

The test is easy and here it is:

• Remove spark plug
• Add a small amount of gas (about oil cap size capful) (gas must be fresh)
• Refit spark plug
• Attempt to start the engine

Mechanic top tip – Plug holes aren’t easy to access, a funnel with an attached hose or syringe makes adding gas to the cylinder a ton easier.

Analyzing the gas shot results

With the test out of the way now we’ll need to analyze the results, and the two results most likely are as follows:

Result 1 – The engine started, or fired (fired – meaning attempted to start). Firing may be identified as the engine not running but smoke seen puffing from the tailpipe when cranking.

This result tells us your ATV likely suffers from a fuel system issue. Bad gas, Choke not working, Faulty fuel pump (if fitted), Blocked gas filter, and Carburetor faults are all high on the list of possibles.

Jump to the Fueling system below and begin your diagnosis journey.

Result 2 – The engine doesn’t start and critically makes no attempt to fire. This result tells us you may have an ignition system or a compression system issue. Since ignition system issues are more common, we’ll diagnose the ignition system first before moving on and checking the Compression system, if needed.

Begin your Ignition system diagnosis below.

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Back to Bucket 5

(I) Ignition System

The ignition system is a collection of components dedicated to producing voltage so that the spark plug can do its thing – fire the spark plug. To that end, the ignition system relies on another important subsystem – the charging system which employs a stator to generate voltage. (More on the stator later)

The ignition system isn’t a one-trick pony, it’s also responsible for adjusting the ignition timing. Meaning it adjusts when the spark is actually fired.

Adjusting the timing is important because it takes a set amount of time for an ignition system to generate a spark at the spark plug and as you know that spark must be added to the mix at a very precise point of the engine cycle.

The faster an engine rotates, the earlier the ignition system needs to begin the spark generating process so that the voltage arrives at the spark plug in good time, and remember this is a moving target, meaning ignition timing needs to be constantly adjusted according to engine RPM.

Yep, your ignition system works like a dog.

Components are listed in order of failure rate (highest first)

The following sections are dedicated to outlining the basic function of the components within the ignition system. We’ll also cover diagnosing and testing the various components.

When faced with a possible ignition system issue makes sense to go straight to testing the spark and we’ll cover that next in the spark plug section.

For many of the following tests, we’ll need a DVOM or power probe. You can find all these tools here on the ATV tools page.

Spark Plug

The spark plug is top of our ignition system troubleshooting list for three reasons, it’s a common cause of no starts, it’s critically important and it’s easy to check.

A plug lives a hard life, consider for a moment what it does and what it must cope with. Thousands of volts pass through it, it must withstand chemical attack, compression pressures, and extreme combustion heat. And yet despite this plugs can last years (we should change them every two years or 1500 miles, of course).

As we suspect we have a spark issue we’ll run an ignition system test. Ideally, we’d use an inline spark tester, that way the whole ignition system is tested, and we’ll cover that below, but first, we’ll check spark MacGyver style.

The MacGyver spark test doesn’t test the whole system conclusively and isn’t a great test for intermittent spark issues. But it works great for no-starts.

The MacGyver spark test is as follows:

• Remove plug wire
• Remove plug
• Examine plug (see plug condition table below)
• Refit plug wire
• Ground plug (make contact with engine raw metal)
• Crank engine over
• Check spark

No spark means we have a problem, but be sure the plug is grounded securely, otherwise you’ll misdiagnose. Improvise with a jumper lead.

Now let’s check the spark using an inline ignition test tool.

Diagnose:

• Remove the plug cap and fit it to the inline tester
• Fit inline tester to the spark plug
• Attempt to start

Checking the test tool window quickly tells us if we have a spark or not.

Reading the plug condition is another useful check.

Spark Plug fouling is a dirty plug and it results in misfiring and no-starts. The reasons a plug becomes fouled in the first place are numerous Here are just some of the common causes of plug fouling:

• Too much oil
• Wrong oil type
• Wrong spark plug
• Bad gas
• Engine wear
• Vacuum leak
• Faulty ignition system
• Carbon build-up

Diagnose: Remove the spark plug and check

Fix: Clean & gap plug (see below)

Flooding is a condition where unburnt gas accumulates inside the cylinder and fouls the spark plug preventing it from firing. Often it’s the plug itself that is at the root of the problem, but there are tons of causes of flooding.

• Excessive use of choke
• Blocked air filter
• Leaking carburetor float needle

Diagnose: Remove plug and check

Fix: Dry out cylinder, clean & gap plug (see below)

I’ve covered how to diagnose and fix a flooded ATV engine previously – ATV flooded with gas

Spark plugs should be cleaned and gapped at least once every six months. Carbon deposits build up on the plug’s electrode and are, as you know a cause of plug fouling and flooding.

To clean a plug use a wire brush to clean the business end, if it’s wet use a flame to clean it or allow it to dry naturally.

Use a plug gapper or feeler gauge to adjust the gap, use pliers to either open the gap or tap it closed.

Coil & Cap

Run a resistance test using a DVOM to determine if it’s within the manufacturer’s spec.

I’ve covered coil testing in greater detail previously. It’s a dirt bike but the process is identical. I test the coil primary, secondary, and resistor cap.

You can check it out here – Dirt bike won’t start when hot

Stator

Run a resistance test using a DVOM to determine if it’s within the manufacturer’s spec.

I’ve covered stator testing in greater detail previously, you can check that out here – Will ATV start with bad stator

Pick-up

Run a resistance test using a DVOM to determine if it’s within the manufacturer’s spec.

I’ve covered pick-up testing in greater detail previously. It’s a dirt bike but the process is identical.

You can check it out here – Dirt bike won’t start when hot

Starter Motor

The starter motor plays a pivotal role in ensuring there’s enough voltage at startup. Without a strong starter motor, the stator and pick-up may not provide enough voltage to fire the spark plug. I’ve covered starter motor testing in greater detail previously and you can check that out here – ATV will only pull start

Ignition Switch

Ignition switch wiring varies from model to model, an ECU will be quite different from a CDI bike. You will require a wiring diagram for your machine to fault find an ignition system systematically.

That said here are a few tips that will help:

• Check wiring at the steering column, flexing commonly causes wiring breaks.
• Try the wiggle test (move the switch loom by hand and see if the condition changes)
• Check power and grounds
• Check block connector pins are clean, dry, and tight

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(II) Fueling System

All engines need fuel, but fuel isn’t just gas alone, because gas won’t burn without air (oxygen). And so gas must be mixed with air, problem is engines are very particular as to the ratio of air to gas. We refer to the ratio as the Air Fuel Ratio (AFR). The sweet spot is 14.7 parts air to 1 part gas and this ratio is known as stochiometric.

It’s the job of the fuelling system to maintain this ratio and deliver it to the engine for every given throttle demand.

The fuelling system your ATV employs will dictate the type of fuel system components your bike has. ATV fuelling systems come in 2 main flavors – the old-school carburetor and the latest and greatest electronic fuel injection (EFI).

While these systems have the same goal, they use different components to arrive there. We’ll take a quick look at how each type goes about it right now.

The carburetor

The old-school carburetor is a mechanical device calibrated very precisely to supply gas to the engine in proportion to the volume of air that passes through it. Carburetors are simple and complicated all at once. But don’t be fooled, carbs are well-tried and tested; while they do have some shortcomings they are generally very reliable.

ATV carburetors come in two main flavors – the mechanical slide and the vacuum-activated Constant Velocity (CV) type.

Carburetors work like this:

CV type – The CV is the more common type of carburetor as they offer better all-round performance and are cleaner to the environment. On CV-type carburetors, the throttle cable is connected to the butterfly valve and when opened creates a vacuum which in turn lifts the slide (and attached needle) and draws gas into the engine through carburetor-housed metering jets.

The main downside to CV carburetors – as they are vacuum-operated, they are less responsive to throttle inputs.

Mechanical slide – The second common ATV carburetor type is the mechanical slide. It operates on the same principle as the CV type carburetor, however, there is one main difference.

The throttle cable is connected directly to the slide and so nailing the throttle lifts the slide with the attached needle and feeds gas to the engine. It is a very direct throttle response and is generally fitted to engines that are performance-focused. However, because it’s so direct in how it opens the slide, it commonly sufferers from bogging (lack of gas), until the vacuum catches up and feeds more gas.

In addition to these main differences, some carburetors may employ manual choke operation while others may have an automatic thermo-activated choke.

All carburetors however suffer from some common complaints, they include having to adjust for temperature and altitude, since both these conditions change the quantity of oxygen in the air, it causes a carburetor engine to run poorly. Typically the operator must make an adjustment to the carburetor. Not practical for most, and so the EFI was born.

EFI

While electronic fuel injection is not a new idea, it is relatively new to the world of small engines. Fuel injection brings some great advantages, it automatically adjusts for air temperature and altitude and it offers sharper performance since the fuel is delivered quickly and atomized, just the way the combustion chamber likes it.

To accomplish this the EFI system which is largely an electronic system employs a computer, sensors to collect data, and a fuel pump and fuel injector to deliver the payload.

A cool byproduct of EFI means bikes can be mapped (ignition and fuel system optimized) for greater power or efficiency with the touch of a button, something not possible with a carburetor bike.

EFI is a robust system. However, some bikes are susceptible to electrical gremlins caused by loose wiring. Fuel pumps wear out as do fuel injectors.

The EFI works like this:

An air temperature sensor (ATS) fitted to the air intake measures the temperature of the ambient air (important as oxygen density is proportional to air temperature)

Baro sensor feeds air pressure reading to the ECU (important, as a change in elevation changes oxygen levels) Baro and ATS are often integrated.

The throttle position sensor (TPS) reports the current throttle position to the ECU.

The throttle body resembles a carburetor in some ways but they don’t serve identical functions. The throttle body is fixed to the engine and houses the butterfly valve with the throttle position sensor attached and also houses the fuel injector.

The electric fuel pump supplies gas to the fuel injector.

The fuel injector is opened and closed by the ECU.

The engine control unit (ECU) manages the whole show. As it’s a pre-programmed computer it can make tons of calculations and very quickly works out the correct fuel quantity for every given throttle demand. By varying the fuel injector duty cycle (“on” time) it can respond to throttle demands.

Components are listed in order of failure rate (highest first)

Gas

Ethanol blended gas is everywhere now; we have no choice but use it. It does cause some problems in a small engine kit that lays idle for weeks on end, and so all small engines should now use a stabilizer in the gas.

The stabilizer helps repel moisture that ethanol attracts and prevents carburetor gumming and hard starting misfiring etc.

Stale ethanol gas is right up there on the list of no-start causes especially if your ATV has been sitting idle for a few weeks.

Diagnose: If your gas is older than a couple of months and your bike has been sitting idle, your gas is likely stale

Fix: Drain gas tank and carburetor bowl and fill with fresh gas

Carburetor

Carburetors cause lots of issues as they get older. They are like wind instruments in that they are finely tuned. If they supply too much or too little gas, your engine will protest. They are of course adjustable within a window but if the moving parts of your carburetor wear they allow air to sneak into the combustion chamber unmetered and this upsets the crucial Air to fuel ratio (AFR).

Carburetors tend to be difficult to diagnose, generally, there’s no smoking gun and often it is a process of elimination.

That said the number one cause of most carburetor problems is dirty jets. Contaminated gas is the usual culprit. Dirty gunge blocked up the tiny brass jet holes which starves the engine of fuel.

Diagnose: One of the first carburetor checks is a fuel flow check.

Check fuel flow as follows:

• Turn petcock off
• Open carb bowl drain
• Turn petcock on
• Check flow

Fix: A lack of gas flow points to a tank blockage, a fuel tap (petcock) blockage, or a carb float valve issue. (See pic)

If on the other hand, you have good gas flow, suspect blocked carb jets. A carburetor strip down and thorough cleaning will fix the issue.

You may find these posts helpful:

• ATV smells like gas
• ATV dies when I give it gas
• ATV only runs with throttle
• Why is my ATV running rich?
• Can I ride with choke on?

Air filter

Ail filters should be checked weekly and even more often in dry dusty conditions. Foam filters may be washed in warm detergent but should only be oiled if the manufacturer recommends it and of course only use recommended filter oil.

Diagnose: Remove the air filter and attempt to start the engine

Fix: Clean or replace the filter

You may find this post helpful:

Can I use WD40 on my air filter

Fuel filter

ATV filters may be inline clear filters where you can see the gas and dirt if present which is really useful for fast diagnosis; however, many ATVs use a carburetor mesh screen filter that can’t be viewed so easily. Many petcocks include an integrated fuel filter bowl.

Diagnose: Access the filter and check for blockage (may need to partially remove the carburetor)

Fix: Clean or replace the filter

You may find this post helpful:

ATV fuel filter not filling up

Fuel pump

Not all ATVs employ a fuel pump; for those that do two types are common, a vacuum-operated fuel pump and an electric pump. Carburetor bikes will either have no pump or a vacuum pump fitted.

Common vacuum fuel pump issues include perished vacuum lines and worn-out diaphragms.

Diagnose: Follow the fuel line from the carburetor back towards the tank. If you have a fuel pump fitted, you’ll find it on this line. Check all vacuum hoses and check for leaks.

Fix: Replace lines or pump

Gas tank, cap, and vent

Gas tanks don’t give trouble so much anymore; most are plastic and so are rust-free. However, faulty gas caps and vents may cause a no-start. A tank needs to breathe and so if a faulty cap or vent seals the tank gas stops flowing and the engine stalls and won’t restart.

Diagnose: Remove the cap and attempt to start the engine.

Fix: Replace the cap and vent

Fuel tap aka Petcock

Most ATV fuel taps are manual and don’t cause issues, that said older style petcocks employ a bowl that catches crap and can become blocked; if your ATV sufferers from a fuel blockage, check the petcock bowl. Some vacuum operated and when the internal diaphragm fails it allows gas to leak into the intake system causing the engine to over fuel and flood.

Diagnose: Remove the vacuum line and check for gas

Fix: Replace Petcock

*Electric fuel pump

Run a resistance test using a DVOM to determine if it’s within the manufacturer’s spec.

*Fuel injector

Run a resistance test using a DVOM to determine if it’s within the manufacturer’s spec.

*TPS

Run a resistance test using a DVOM to determine if it’s within your manufacturer’s spec.

*ATS

Run a resistance test using a DVOM to determine if it’s within the manufacturer’s spec.

You may find this post helpful – ATV won’t start when cold

*Baro

Run a resistance test using a DVOM to determine if it’s within the manufacturer’s spec.

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Back to Fueling System

(III) Compression System

This section is last for good reason, it is the least likely system to cause an issue; however, if your issue does lie within this section there’s a good chance your problem is a serious one. That said there are some easy-to-fix issues within this section and we won’t meet trouble halfway.

What is compression?

Compression is an engine’s ability to contain the pressure created by the piston, as it squeezes and squashes the contents of the cylinder (air & fuel) into the combustion chamber (area at the top of the cylinder around the spark plug).

Compression is important, the squeezing helps warm the air and prepare it for ignition (explosion).

An engine with low compression will therefore struggle to start or likely won’t start at all. The reasons for low compression are covered below together with how we go about testing same.

You should note, compression test readings vary from one engine maker to another and so you will need to know what your engine compression specs are. Generally speaking, a reading below 100 Psi is deemed low compression. That said some engines may have a min far above 100 Psi, so check your specs before condemning.

Components are listed in order of failure rate (highest first)

You may find these posts helpful:

ATV has spark and fuel but won’t start

How much compression should an ATV have?

When faced with a possible compression issue makes great sense to just go ahead and run a compression test. Doing so usually points us to the problem component.

Compression Issue

The problem is some engines don’t lend themselves to compression testing and here’s why.

A compression releases assembly also known as a decompression valve kicks in during cranking to lower compression so as to lessen the workload on both the starter motor and battery.

The problem is, this lowering of compression also skews the compression readings and renders them useless. In fact, many manufacturers won’t offer compression specs if their engines are fitted with decompression valves. In these cases, we use a leakdown tester and so I’ll cover both test types in this section.

Assume you have a decompression valve fitted if you can’t find compression specs for your engine; if that sounds like you, you’ll need to run a leakdown test. Indeed a leak-down test is my preferred way to test for compression issues.

Compression test

To run this test you’ll need some tools, a compression test kit or a leak-down test kit. If you use a leakdown tester you’ll also need access to compressed air. Either way, you’ll find the tools needed here on the ATV tools page.

We’ll run the compression test first. This test is a two-part test. First, we run the dry compression test, and then we run the wet test.

The dry test is as follows:

• Remove spark plug
• Ground coil (prevents coil damage)
• Fit compression tester
• Choke off
• Throttle wide open
• Crank over 6 – 10 times
• Read and note the highest reading

Now we run the second part of the compression test – the wet test is as follows:

• Add a cap full of engine oil to the cylinder
• Repeat the dry test as above
• Read and note the highest reading

Now we need to make sense of the results. One of three results is likely, they are as follows:

1 Readings are the same but compression is low – If the wet compression readings are the same as the dry reading from the first test (or close) and the compression readings are below spec (as per your engine maker), then it is likely you have a top-end issue.

Go ahead and check your spark plug is tight, the valve lash is within spec, and the head gasket is ok.

2 Readings are different and compression is low – If, on the other hand, the readings are very different meaning the wet compression readings are significantly higher. Then it is likely your engine suffers from worn rings or piston or cylinder or combo of all three.

You’ll need to strip your motor for inspection.

3 Readings are the same and compression is normal – If your readings test well above 100 psi and both wet and dry tests are similar, Congrats! Low compression isn’t your issue.

Instead, I’d direct my attention to engine timing.

Leak down test

A leak-down tester is likely a faster and more conclusive way to both test and pinpoints the root cause of a suspect compression issue. In this test, we’ll fill the cylinder with compressed air and we’ll use the test tool to measure the cylinder’s ability to hold pressure over a given time period.

See the leak-down tester I recommend here on the ATV tools page.

But before we do that we’ll need to set the engine to Top Dead Center (TDC).

I’ve covered setting the engine to TDC previously and you can check that out right here – ATV valve adjusting

The bonus of the leak-down tester is its ability to point to the area at fault. In a problem engine, the compressed air will be heard to leak from the cylinder. All we need do is identify where it’s leaking from.

Air leak diagnosis is as follows:

• Spark plug – Tighten the spark plug
• Oil cap or dipstick – Worn piston rings
• From muffler – Exhaust valve issue (worn seat or adjustment)
• From carburetor /airbox – Intake valve issue (worn seat or adjustment)
• Between cylinder head and block – Head gasket failure

With the leak-down test complete, we should now have a handle on the component at fault. See the list of likely culprits below and what we’ll need to do to fix them.

I will include links to tests and tools as needed to test, repair and or replace components.

Spark plug

If you are here because the leak down test pointed to a leak around the spark plug, you are lucky, this is an easy fix. A spark plug provides a spark you already know that, but it has another job, it must seal the combustion chamber.

A loose plug will allow compression escape. Truthfully a loose plug may not be the most common cause of low compression but it is easy to check and a super-easy fix, and that’s why it’s first on our list.

Tools needed – for this we’ll only require a plug socket and ratchet. You’ll find one here on the ATV tools page.

Diagnose – A loose plug will allow compression to escape which may in fact be heard as the engine cranks over. A damaged spark plug washer is also a possible reason a spark plug fails to seal. Remove and check the washer is ok.

The fix – Check the plug is tight.

Valvetrain

The valvetrain comprises various components but the two most common valve train issues associated with low compression are damaged valves and poor valve adjustment. Valve adjustment is also known as valve lash.

If the leak down test pointed to the exhaust or carburetor then it’s the respective valve that is at issue. A valve that’s too tight, meaning it’s held open will lower compression and cause a leak when tested. That’s one explanation for a valve leak and the other is a bad valve face or seat.

We can eliminate one of these easily by testing valve lash and I’ve covered that below, but remember if valve lash is within spec, it’s likely a bad valve seat or valve face that is damaged and it will need to be replaced.

Lash should be checked before assuming we have valve damage.

Valve lash

Valve lash is set at the factory but as an engine wears as you can imagine lash moves out of spec. For most ATVs lash should be checked every year or about 1500 miles, most aren’t checked. However, overhead cam engines require less attention.

While excessive lash could cause a no-start it won’t cause a low compression issue. However, a tight valve will.

A tight valve is less common than excessive lash but it remains a very good explanation for low compression and so well need to check and adjust it as necessary.

I have covered this exact topic in greater detail previously and you can check out that post right here – ATV valve adjustment in 6 steps.

Timing

The timing of your engine is obviously important. The top half of the engine (cam and valves) are very precisely timed to the crankshaft and piston. If the valves aren’t opening when they should, the engine won’t run or may run but run poorly. This will also lead to poor compression readings.

Not only that, an interference engine may cause your valves and piston to collide, that’s never a good outcome. An interference engine means the valves and piston use the same space, all be it at different times, so you can see how important timing is to an interference engine.

If you suspect a timing issue, we’ll need to get that checked, I’ve covered checking engine timing previously and you can check that out here – How to tell ATV jumped time.

Head gasket

A blown head gasket will cause a drop in compression. The head gasket is a graphite material sandwiched between the cylinder head and the jug. It helps seal and prevents the mixing of oil, coolant, and combustion passages.

Gaskets fail with age but also may fail as a result of an overheating issue or lack of proper coolant system maintenance. Straight water in coolant systems causes corrosion and that’s a common cause of premature gasket failure.

Head gasket failure is common however, you should have some additional symptoms prior to the no-start. Common symptoms include coolant loss, overheating, hard hot starting, white smoke from the tailpipe.

A leak-down test is great at exposing head gasket failures, and also showing where it has failed. Bubbles in the coolant system mean as you know the gasket has failed between the coolant passage and combustion chamber.

Sometimes of course it may not be conclusive as the engine may need to be hot before the leak presents itself and so if I suspect such a gasket failure but can’t identify it with the leakdown test ill use a chemical combustion leak test kit.

You’ll find a combustion leak test kit I recommend here on the ATV tools page.

Rings

Worn rings are the last thing any ATV owner wants to hear. Common symptoms include hard starting, long crank, oil consumption, blue smoke, lack of power, spark plug fouling, and misfiring.

If your leak-down test blows air through the dipstick or the wet compression test shows a large difference when compared to the dry test, it likely means an expensive tear-down and a rebuild.

You are also looking at a couple of weeks of downtime given parts lead time and workshop schedules, etc. It is possible to DIY it but you’ll need a workshop manual and some special tools like a torque wrench, ring compressor, and feeler gauge.

Battery & Starter Motor

A strong battery and starter motor are important components for easy engine starting. Both components are key players and directly affect two of the three systems critical for internal combustion engines to run.

A battery and starter motor together provide all the power and muscle to crank over the motor, but critically they must do so with sufficient speed to cause two important things to happen.

1 the engine must crank over fast enough (Min 400 rpm) in order to excite the stator and create a voltage strong enough to fire the spark plug.

The pick-up also relies on a spinning crankshaft to produce a voltage which is used to signal the ECU/CDI and fire the spark plug.

2 the engine must crank over fast enough to create sufficient compression to prepare the air/fuel mixture for ignition.

Any issue that prevents the engine from cranking over fast enough may prevent the fuel igniting.

A fast way to eliminate this possibility is to try jumpstarting; if the engine starts, you know you have a battery issue, which is more likely than a starter motor issue. I’ve covered battery testing at length previously in this post, you can jump to it here battery testing.

I’ve covered starter motor testing in greater detail previously and you can check that out here – ATV will only pull start

You’ll find all these tools here on the ATV tools page.

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Back to Compression System

I’ve covered a ton of other common ATV issues and you can check them out on the ATV maintenance & troubleshooting page

You find the following posts helpful:

• ATV No-Start page
• ATV maintenance
• ATV care page
• ATV tools page
• ATV parts page

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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The post ATV Won’t Start – Mechanics insider tips that actually work appeared first on ATVFixed.com.

A constantly flooded ATV is a real pain in the ass, not to mention it’s bad for engine health. Flooding causes gas to dilute the engine oil, and that, over the long term, can be terminal. Anyhow you are in the right place, I’m a mechanic, and I think we can get this puzzled out right now.

ATV gas flooding is a symptom closely associated with the following common ATV issues:

• Clogged air filter
• Spark plug fault
• Soft battery
• Bad gas
• Coil fault
• Carburetor fault

In this post, you’ll learn why your ATV floods with gas, you’ll learn how to diagnose the root cause, and how to un-flood your bike quickly. In addition, you’ll learn some mechanics tips for avoiding flooding in the future.

Symptoms of ATV Gas Flooding

I think you have this one covered. The symptoms are obvious to most, but there may be a few in the list below that are tangential to flooding.

• No start
• Long crank
• Stink of raw gas
• Gas leaking under the engine
• High oil level
• Hydro-locked engine

What Causes ATV Flooding?

In many cases, an ATV floods because the engine needs a tune-up, and so if you haven’t serviced your ATV in more than twelve months. A full tune-up now is a great place to start.

Generally, a flooded ATV is a symptom of an underlying problem; it is not the root cause. In this section, we’ll look briefly at some of the more likely root causes of ATV flooding.

They include:

• Poor maintenance – An ATV should be serviced every twelve months.
• Incorrect start procedure – Using excessive choke while starting, especially when the engine is warm, can lead to flooding.
• Faulty choke – A choke manual or auto that’s sticking in the “On” position may also cause hot start flooding.
• Clogged air filter – A dirty air filter is close to the top of this list for a good reason. A blocked filter causes a rich fuel condition and flooding.
• Bad gas – Old gas goes stale and loses its ability to ignite. This may result in flooding of the cylinder and spark plug fouling.
• Fouled spark plug – A spark plug that doesn’t fire won’t ignite the gas, and the most common cause of a nonfiring plug is fouling.
• Battery fault – While many bikes will run with a low battery, starting may cause some issues. A strong battery is required in order to achieve at least 400 rpm. That’s important for two reasons, sufficient RPM is needed to generate a strong spark, and secondly, a min of 400 rpm is required to create sufficient compression in the combustion chamber.
• Faulty carburetor – A common carburetor over-fueling fault is caused by an incorrectly adjusted float height. Another common issue is a worn and leaking carb needle valve. These types of carburetor faults are associated with hydro-locking.
• Mechanical issue – Low compression will result in a no-start, and a no-start means gas is flooding the engine.
• Electrical issue – A bad plug cap, coil wire, coil, Stator, CDI module, and pickup are all possible causes of flooding.

Diagnosing The Cause Of ATV Gas Flooding

As we’ve seen in the previous section, the list of possible causes is wide-ranging. In this section, we’ll attempt to diagnose the root cause. It makes sense to check the most common and also easy to check items first, before checking the less likely issues and harder to test. And so that’s what we’ll do next.

Go ahead and check the following:

• Starting procedure – This may seem insignificant, but if the bike is new to you, the starting procedure may be different. The fix – check your owner’s manual for the correct ignition system and choke use (if manual choke fitted).
• Air filter – A choked-up air filter will prevent airflow and, conversely, will flood the cylinder with gas. The flood of gas compounds the problem by fouling the spark plug. The fix – remove, check, and clean the air filter. It is common to oil ATV foam filters, but air filter oil should be used, not engine oil. Never wash or oil a pleated paper air filter.
• Spark plug – The spark plug should be cleaned and the gap checked every three months. The plug should be changed every two years, and check your plug type is correct. Spark plugs are specific to your engine. The fix – remove, check the gap, and clean or fit a new plug.
• Check fuel quality – Poor fuel quality is a very common cause of no starts, likely the most common cause. If your gas is older than a couple of months, there’s a very good chance your fuel is stale and is fouling the plug, causing a no-start and flooding. The fix – drain the gas tank, and carburetor bowl and use fill with fresh gas. Adding a gas stabilizer helps keep gas fresh for twelve months.
• Check compression – Low compression is at the bottom of the list as it’s less likely and harder to diagnose and fix. To diagnose successfully, you’ll need to run a compression test, and you can check that procedure here.

How To Un-Flood ATV Engine

When it comes to clearing a flooded ATV engine, we have three options:

1 Open throttle – Fully open the throttle, but leave the choke off; now, crank the motor over. The open throttle increases airflow to the engine and helps dry out the cylinder. If the engine doesn’t clear and start after two or three attempts, I’d try one of the other strategies below. Excessive cranking will run the battery down.

2 Wait – Simply walking away and allowing time to dry out the cylinder usually works. Waiting anywhere from fifteen minutes to a half-hour does the job.

That said, if there is an underlying problem causing the flooding, then you may be visiting this problem again before long. Remember, when starting a flooded engine, don’t add any choke.

3 Clear cylinder – Clearing the cylinder will require a few tools and a little effort. You’ll need a plug wrench and a shop rag.

The process is as follows:

• Go ahead and remove the spark plug
• Disable the coil by removing the coil power feed. (failing to disable the coil risks fire and also risks overloading the coil)
• Place a shop cloth over the plughole
• Crank over the engine to expel the raw gas

Now go ahead and clean, gap the spark plug, and refit.

Mechanics Tips To Prevent ATV Gas Flooding

Here are my top tips for keeping your ATV in great shape and free from flooding

• Tune-up your engine
• Turn off Petcock (gas tap) when bike not in use
• Use a gas stabilizer
• Clean and gap spark plug regularly
• Check spark plug is correct heat range

When storing your ATV, it pays off handsomely to pay particular attention to the fuel system.

• Use gas stabilizer – Fill the gas tank before winterizing your ATV and add a gas stabilizer to the gas tank. Run the engine a while to distribute the mix throughout the fuel system.
• Use battery maintainer – use a smart battery charger to keep the battery in top shape.
• Turn off the petcock when the ATV is not in use
• Park bike undercover and but use a breathable cover

You may find the following posts helpful:

ATV carburetor flooding

ATV won’t start after washing

ATV won’t jumpstart

I wrote a ton of ATV repair guides. Hopefully, you won’t need them, but if you do, we have you covered.

ATV Repair Guides

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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The post ATV Flooded With Gas – Here’s why and the fix appeared first on ATVFixed.com.

Pull starting a big motor isn’t fun at the best of times, but when an ATV engine won’t pull start your efforts can feel like a frustrating waste of time. You’re correct to seek advice, many no-star problems are simple ones. Either way, I’m a mechanic and we’ll get to the bottom of this problem right now!

An ATV may not pull start for the following reasons:

1. Too much engine oil
2. Pull starter assembly fault
3. Ignition system fault
4. Fuel system fault
5. Mechanical Issue

In this post you’ll learn some common causes of an ATV that won’t pull-start, you’ll learn how to quickly diagnose where the issue lies and how to go about fixing it.

ATV No-Start Diagnosis

An ATV may not pull start for several reasons and in this section, we’ll try and get your particular problem to fit into one of three buckets. But just before we get to that we should be sure we have a problem. It is easy in the heat of battle to miss or assume something and so here s a short list of common no-start basics that are often overlooked.

• Gas valve “On”
• Choke “On”
• Ignition “On”
• Fuel level Ok?
• Is fuel fresh?
• Plug wire on securely

Not pulling starter with enough oomph – It should be noted an ATV engine needs to turn over at approx. 400 RPM in order to build sufficient voltage to create a strong bright spark at the spark plug. Less RPM means a weak spark and that will make starting the engine a challenge.

That’s all the simple stuff out of the way. Let’s dig a little deeper and check and see which bucket fits your symptom best.

Bucket 1

Pull starter feels normal but the engine just won’t start – If your pull starter feels normal but just won’t fire, your ATV most likely suffers from a fueling, ignition, or compression issue. Pretty wide-ranging, I hear ya. But go ahead and follow the link to jump down the page where I show you how to quickly find which of these issues you have.

Bucket 2

Pull starter feels funny, it’s stiff and the engine barely turns over – An engine that’s difficult or stiff to turn over is on the face of it, quite serious. That said there are some easy to fix innocent explanations for the stiffness. If the stiff pull starter sounds like your problem, go ahead and jump to the explanations below.

Bucket 3

Pull starter pulls freely and isn’t catching and turning over the engine as usual – This is a common condition and is commonly associated with worn pulley pawls. If your pull starter feels funny and you think this might fit the description of your issue, go ahead and jump to the explanations below.

Bucket One – Pull Feels Normal, but engine won’t start!

You are here because your pull starter feels normal, but she just won’t start – Great! You are in the correct place. All ATV engines require three things in order to start and run smoothly.

1. Fuel – They need an air/fuel mix to the correct ratio
2. Spark – They need a strong spark fired at the correct time
3. Compression – The combustion chamber must have the ability to contain the compression

One of these three is at fault and is the root cause of your no-start ATV.

We could check each of these three systems individually but that takes a ton of time and effort. Instead, we’ll run a test that eliminates one or two of the three. The test is called the gas shot test.

Gas Shot Test

I run this test in the workshop, it saves a ton of time and effort and requires little in the way of tools. The test is as follows:

• Remove spark plug
• Add a cap full of fresh gas to the cylinder (syringe or small funnel helps)
• Refit spark plug
• Attempt to start the engine in the usual way

Note: it’s important to use fresh gas.

After your attempt to start the engine, two outcomes are likely:

1 Engine Started – The engine started or attempted to start it’s known as firing. Starting or firing both means your ATV likely suffers from a fueling issue. A choke issue is possible, but stale gas is the most likely, especially so if the gas is older than a couple of months. Draining the gas tank, carburetor bowl and refilling will solve the problem. Use a gas stabilizer in the fuel system to help guard against stale gas.

(Firing may be described and identified as follows – engine not running and smoke puffing from the tailpipe as the engine is cranked over.)

(Cranking may be described as – engine rotating by pull start or starter power, but the engine isn’t running.)

2 Engine Does Not Start – Engine made no attempt to start whatsoever. If this is the case, your ATV likely suffers from compression or an ignition system issue. An ignition issue is far more likely, and a fouled spark plug is the most likely ignition problem. And that’s what we’ll check next.

Fouled Spark Plug

A fouled plug is a common problem in all small engine kit and occasional fouling isn’t a concern, if however, it happens a lot then you may have an underlying issue. Spark plugs need a little love from time to time. Typically a plug should be cleaned and gapped every 3 to 6 months and replaced every two years. Of course, I live in the real world and we both know that in most cases doesn’t happen.

A consistently fouling spark plug may be caused by all sorts of reasons from wrong plug type to poor quality gas and a ton of other reasons in between.

To clean and gap a spark plug, you’ll need the following tools:

• Plug wrench
• Wire brush
• Feeler gauge or plug gapper tool

I’ve covered cleaning and gapping a plug in greater detail in this post “Why is ATV spark plug black?”

Check Spark

To check the spark you’ll need to remove the spark plug and ground the plug on the engine.

The process is as follows:

• Remove plug wire
• Remove spark plug
• Reattach plug wire to loose plug
• Ground the spark plug threads against the engine metal (metal to metal is known as grounding)
• Ignition switch “On”
• Have a helper pull start the engine
• You check plug spark

If you have a spare plug to hand, check spark using it also.

It’s critical to ground the spark plug well, getting this wrong will lead to an incorrect diagnosis.

Two outcomes are likely:

1 The spark plug works great – It emits a bright blue spark. If this is the case you’ll need to move on and check compression, the ignition system works fine.

2 Spark is weak or non-existent – A lack of spark is good news, it means you know why your ATV isn’t starting. The ignition system however includes a few components any of which could prevent spark if failed. I covered checking each component in the following post, it’s a dirt bike but the setup and testing is identical. “Dirt bike won’t start when hot”

If you need to check compression you can check out this post where I outline the process. “ATV has spark and fuel but won’t start.”

Bucket Two – Pull Feels Really Stiff!

You are here because your pull starter feels really stiff – Great! This section is for you and here you’ll find more info on each of the more likely possibilities together with a broad outline of the fix.

First, we’ll look at the easier less serious causes:

• Too much engine oil – Adding too much oil is common and it creates excessive back pressure and difficulty starting. The fix – drain off the excess oil.
• Hydro-locked engine – This is a condition where the cylinder fills with fluid (raw gas usually) but in ATVs with radiators, the hydro-locking could be coolant and that usually means a failed head gasket. Raw gas usually means a failed carburetor float and needle issue. Either way, fluid in the cylinder prevents the piston from moving. To test for this condition, remove the spark plug and see if fluid spills from the cylinder. The fix – replace the head gasket or replace the carburetor needle valve.
• Valve lash off – Valves as you know open and close in sequence and at very precise times. When valve adjustment is off it may cause hard to turn over the engine and hard or no start. The fix – Check and adjust the valve lash.
• Timing off – Engine timing is important, some engines may employ timing chains to time crankshaft to camshaft others may employ internal gears. It is possible for timing chains to jump a tooth and that may cause a no-start and difficult cranking. The fix – check and adjust timing.
• Stuck closed exhaust valve – Valves sometimes stick closed or open when an engine lays up, say over winter. When pull starts, the closed exhaust valve prevents compression from escaping and in such circumstances, the engine would be difficult to turn over. The fix – release the valve.

And now for a list of the more serious causes:

• Stretched timing chain
• Camshaft damage
• Crankshaft damage
• Piston and bore damage
• Faulty transmission clutch

Checking ATV crankshaft timing marks

Checking ATV camshaft timing marks.

I’ve covered checking the timing in greater detail in the following post “ATV has spark and fuel but won’t start”

Bucket Three – Pull Not Catching!

You are here because your pull starter feels funny, it’s not catching and cranking the engine over – You’re in the right place!

To confirm this you’ll need to remove the pulley assembly and check both the pawls and the receiver on the engine side. Replacing pawls is a simple job, but you will need replacement pawls and they are engine specific. Other common pull start assembly issues include a broken recoil spring, symptoms of which include a cord that doesn’t retract and a broken pull cord that is self-explanatory.

You may find the following posts helpful:

Start a dirt bike without kickstart

Will dirt bike start with low compression?

How to tell if ATV fuel pump is bad

ATV will only pull start?

ATV flooded with gas

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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The post ATV Won’t Pull Start – Solved! appeared first on ATVFixed.com.

As you’ve likely guessed, there are a few areas of an ATV we need to avoid when washing. But don’t worry about it, this is a simple problem to fix and we’ll get it figured out very shortly. I’m a mechanic, I must have washed hundreds of ATVs over the years and I’ll share a few insider hacks I learned along the way.

An ATV that refuses to start after washing likely suffers from a wet ignition system. Drying the coil, plug wire, plug cap, and spark plug will likely solve the problem. WD40 helps repel dampness from ignition system components.

In this post, you’ll learn why your ATV won’t start after washing, how to diagnose it and what you can do to fix it, right now. In addition, you’ll learn a simple trick to prevent this from happening in the future and ATV components to avoid when power washing.

Is Your ATV Cranking Over?

If your ATV cranks over then it’s likely your engine suffers from a wet ignition system and that’s covered below.

What does cranking over mean? Cranking over means the engine turns over when you hit the start button, but the engine fails to actually run.

If your engine isn’t cranking over, meaning, you hit the start button but nothing happens, then you likely have a loose battery terminal, neutral switch wiring, or starter solenoid issue and that’s covered below also. And so, if your engine doesn’t crank, go ahead and jump to no crank after washing.

Why Does a Wet Ignition System Prevent Starting?

Water makes a good path for voltage and so voltage from a wet ignition system will short and ground out on the engine. An ignition system that’s shorting out means that voltage never gets to the spark plug and so never gets the chance to create a spark.

Diagnosing Wet ATV Ignition System

Checking for a damp ignition system is simple. Gain access to the plug wire, you may need to remove a side cover. Then go ahead and remove the plug wire by twisting and pulling, checking both the spark plug and inside the coil wire cap for water, and checking the coil itself.

Drying Out Wet ATV Ignition System

We have a ton of options to dry out an ATV ignition system.

• Compressed air – Compressed air is the best way to dry out a wet ignition system.
• Manual drying – Using kitchen towel to manually dry the plug and around plug hole, inside the coil wire, the coil wire itself and the coil which is usually tucked up out of the way, but depending on how enthusiastic you were washing, it may be wet too.
• Self repair – If you can spare the time, leave your ATV indoors and the ignition system will dry out naturally, but that will depend on how much moisture is in the air.
• WD40 – WD40 repels moisture, pulling the coil cap and rinsing with WD40 will drive the moisture out.

Additional issue associated with a wet ignition system

In addition to a wet ignition system, your ATVs engine likely suffers from flooding also. Not flooding with water, but flooding with gas.

And the reason is obvious once you understand what’s going on. Cranking and cranking an ATV engine that refuses to start causes the cylinder to fill with gas. The soaked cylinder washes the spark plug with gas, fouling it.

And now we have a situation where even if the ignition system was dry, the engine wouldn’t start.

This condition is known as flooding and another term you’ll hear associated with flooding is a fouled spark plug. Flooding doesn’t happen to every engine but if you’ve been cranking hard and using the choke, flooding and plug fouling is very likely.

Clearing a flooded engine

In many cases, a flooded engine will fix itself as the gas inside the cylinder evaporates and the spark plug dries out. Usually, a half-hour does the job. But some engines may need some help.

As an alternative, here’s another easy fix that helps dry out the cylinder.

Crank over the engine with the throttle held wide open. Don’t add any choke.

If that doesn’t help, you’ll need a plug wrench. Unflooding an engine isn’t a difficult job but you will need to gain access to the spark plug. You should note, cranking over the engine with the spark plug removed will cause raw gas to spray from the cylinder, so you’ll need to perform this in a well-ventilated area and wear eye protection.

But there’s an even more serious risk, and that’s fire. The ignition system should be disabled before cranking over the motor. Removing the spark plug and cranking the motor will cause the coil to attempt to ground and that causes a spark. A spark and raw gas is a major risk.

In addition, cranking the motor without disabling the coil risks overloading and damaging the coil. Instead, the coil power supply should be disconnected, this prevents both risks.

The process is as follows:

• Remove plug wire
• Remove plug
• Remove coil power side feed (typically a block connector)
• Place rag over plug hole
• Crank over engine
• Use wire brush to clean spark plug
• Check plug gap
• Refit the spark plug and wire
• Refit coil power feed

Job done!

ATV Components To Avoid When Washing

Ignition system components don’t like the water you know that. And so it’s best to avoid them altogether. You can still power wash your ATV engine but we’ll need to be mindful of a few components. They are not the only components that need to be avoided. Power washers are powerful especially heavy-duty washers 3000 psi plus, that’s plenty enough pressure to drive water into components like sealed bearings, carburetors, air boxes, and filters.

I don’t like to power wash engines and axles too often, sure we need to remove muck but driving high-pressure water at mechanical components regularly isn’t a great plan.

Use low pressure around the following components:

• Engine
• Transmission
• Axle
• Brakes
• Chain

Avoid these components:

• Coil
• Spark plug
• CDI unit
• Carburetor
• Air box
• Battery
• Dash clock
• Throttle controls

Pre ATV Power Washing Tips

WD40 – WD40 as you know repels moisture and spraying all electrical components is a great way to prevent dampness. This is a great way to help prevent dampness before a power washing session, but it is also a wise move in preparation for storage or bad weather.

Shield components – Wrapping components in plastic prior to washing works too.

No Cranking After Washing

No cranking, as you know means your engine doesn’t turn over when you hit the start button. And as said at the beginning, that usually means something has come loose accidentally in the pressure washing. That’s not uncommon as pressure washers pack a punch.

I’m not a big fan of washing unless the psi is turned way down. High-pressure washing is OK for stripping decks but not great for ATV bearings, carburetors, and electrical components.

Diagnosis

For the following line of diagnosing I’ve assumed your dash lights (ignition lights) come on when you turn the ignition to position two.

If that’s not the case, check the following:

• The battery is connected and terminals tight
• The main fuse is Ok
• The ignition switch wiring is connected

I’ll assume you have power at the ignition, and with that said, there are two likely outcomes when you hit the start button:

1 The bike makes a clicking sound – Repeated clicks suggest your battery is at issue. And assuming your battery was in great shape before the washing, it’s safe to say the fault is most likely a loose battery terminal or main fuse holder issue.

A single-click sound suggests loose starter solenoid wiring. Some bikes place the solenoid under the fender which is in the firing line for water and so solenoid failure is common too.

That said finding your solenoid under the seat doesn’t eliminate it from the list of suspects.

ATV Starter Solenoid Test

Crossing the solenoid is a fast way to test for a failed solenoid. But you’ll need to use caution, this test bypasses all safety lock-out systems, so be smart when using this test – Place the bike in Neutral with the Park brake set to “On”.

Test Solenoid as follows:

• Locate solenoid, often located under the seat or under rear fender
• Place bike in Neutral and brake On
• Use a metal shaft screwdriver with a plastic handle to cross the poles momentarily as per picture

Expect the engine to crank over

One of two results are likely:

• If the engine cranks over without issue, a faulty solenoid is the most likely issue. However, a faulty wiring circuit, such as a disconnected start button wiring is still possible.
• If however, your engine still won’t crank, suspect a bad battery, hydro-locked engine, or mechanical issue.

2 No sound from the engine at all, nothing – No noise at all likely means your start button isn’t grounding the starter solenoid and so power isn’t flowing to the starter solenoid. A wiring issue at the transmission neutral switch is possible (if applicable), or a faulty start button itself. Check for loose wiring.

Other Possible Causes Of No Start ATV

• Water inside the CDI unit /ECU
• Water inside the stator housing
• Pick-up coil wiring loose
• Water in the air filter – Water-soaked air filter will prevent starting
• Displaced wiring – Pressure washing may have disconnected ignition system wiring
• Battery issue – Washing may have disconnected battery wiring
• Water in the carburetor – Water inside the carburetor will cause the engine to stall

You may find the following posts helpful:

Okay to pressure wash an ATV?

Why is ATV plug black?

ATV won’t jumpstart

Will ATV start with bad Stator?

Can ATVs go in water?

ATV won’t pull start

ATV flooded with gas

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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• Will Dirt Bike Start If Timing Off? Run this test

The post ATV Won’t Start After Washing – This will fix it! appeared first on ATVFixed.com.

Good spark and fuel are, as you know, not enough to start an ATV engine. That said, you are on the right track, and as a mechanic, I, too, would begin troubleshooting by checking the spark and fuel supply. Spark and fuel issues are the most common ATV no-start causes.

That said, there’s one more ingredient we need to consider, and in this post, we’ll look at all three ingredients needed to start an ATV engine in more detail.

An ATV engine that’s getting spark and fuel but won’t start likely suffers from low cylinder compression or incorrect engine timing. Poor valve lash, failed head gasket, and worn piston rings are common causes of low cylinder compression.

There are many possible reasons, of course, for an ATV no-start, and in this post, we’ll attempt to cover the most likely causes.

ATV Engine Needs Three Things To Start

An ATV engine needs many components and sequences to play their part for the engine to burst into life. When troubleshooting a no-start, technicians are trained to focus on the Holy Grail, that’s, fuel, spark, and compression systems.

1. Fuel
2. Spark
3. Compression

1 Fuel

Fuel is not just gas. Since an engine won’t burn gas alone, the gas must be mixed with oxygen (air), so we describe the mixture of gas and air as fuel. The gas element of the fuel must be fresh. Most folks don’t know that gas goes stale after a couple of months (and earlier, depending on how it’s stored), and if you don’t ride regularly, it is very likely the gas in your ATV tank is stale.

Stale gas lacks oomph; it isn’t as combustible as fresh gas and so starting an engine can be challenging, especially when the engine is cold.

So without fresh combustible gas, an ATV will struggle to start.

2 Spark

Fresh gas is great, but without a spark to ignite our fuel mixture. Our engine isn’t going to fire with just any old spark, no sir, that’s not going to do it. A weak spark will be extinguished by the fuel mix instead of igniting it.

3 Compression

The third and final ingredient is compression. Without a compressed combustion chamber, the mix isn’t confined or heated to a point where conditions are perfect for ignition, and so the starting sequence of ignition, combustion, and power stroke doesn’t happen.

Diagnosing ATV Spark & Fuel But No-Start

Checking spark and gas is among the first checks to make when diagnosing a no-start. As said earlier, you are on the correct track, and very shortly, we’ll have this figured out.

Before we get knee-deep in diagnosis, let us make some simple checks first, and here’s why. As a trained technician with twenty-five years under my belt (and, of course, been bitten a few times), I like to check a fact is a fact.

And so, with that said, I like to verify some common errors; I know this may seem trivial, but I’m often surprised by the errors made by simply making assumptions. And so, work with me here, and let’s assume nothing for the next few paragraphs.

Basic ATV No-Start Checks

Starting Procedure

Starting most engines will require using some type of gas enrichment to counteract the oxygen-rich mix associated with cold starts.

An engine loves a mix of air (oxygen) to the gas of 14.7 to 1 (14.7 parts oxygen to 1 part gas). It’s known as the AFR (Air Fuel Ratio).

Since cold air is richer in oxygen than warm air, cold engine starts are an oxygen-rich environment. Conversely, the engine under these conditions suffers from a lean condition. Lean means the gas component of the mix is insufficient.

And since cold engine starts naturally offers the engine greater oxygen, we need to adjust the mix so that the ratio is back in line with the optimum 14.7 to 1 AFR ratio.

Adjustment is handled differently by different engines. Some do it automatically, and others require the operator to adjust manually.

The adjusting approach is also handled differently by different engine makers; some add extra gas while others restrict airflow to the engine; it’s known as a choke. More oxygen means we need to add more gas.

Fresh Gas

Just before we get to diagnosing the choke, I should point out how important fresh gas is and how common stale gas is, especially in engines that lay idle for long periods. As said, modern gas is blended and goes stale surprisingly quickly, and depending on where it’s stored, it may go stale within as little as a month. If your ATV has been sitting idle for some time, expect a fuel issue as the root cause.

Draining old gas and refilling with fresh, consider adding a fuel stabilizer to keep the gas fresh for about a year.

Choke Diagnosis

Choke diagnosis consists of first checking whether the correct starting procedure is being used and, if so, if the choke system is working correctly. I like to check the air filter early in the troubleshooting procedure; removing the filter and attempting to start the engine is a fast way to eliminate it as a possible issue.

Then I’ll move on and run the following checks.

Correct Cold Start Procedure – You likely already know the correct procedure, but if you are unsure, go ahead and google your make and model to verify. Sure, you say, but my ATV started fine without choke previously. I say OK, but is the weather colder now? If so, the engine likely just needs some choke.

Remember, the lower the ambient temperature, the harder your ATV will be to start.

Is Choke Working Correctly? – I understand this can be difficult to answer and will require some stripping to access the carburetor, etc., but I got you covered; there’s a shortcut known as the “Gas shot.”

Gas Shot – The gas shot test is a simple test where we pour fresh gas into the cylinder. The gas shot test is an elimination round and answers many questions very quickly. I use it in the workshop all the time. The idea is simple, and here it is:

• Remove spark plug
• Add small amount of gas (about oil cap full) (gas must be fresh)
• Refit spark plug
• Attempt to start engine

Mechanic top tip – A funnel or syringe makes adding gas to the cylinder a ton easier.

With the test out of the way now, we’ll need to analyze the results, and the two results likely are as follows:

1 – The engine started, or fired (fired – meaning attempted to start). Firing can be identified as the engine not running, but smoke is seen at the tailpipe when cranking.

This result tells us that your ATV suffers from a fuel issue. Bad gas, Choke not working, Faulty fuel pump (if fitted), Blocked gas filter and Carburetor fault are all high on the list.

If this sounds like your problem, great! Go ahead and examine your fuel system, remembering stale gas is the number one fuel-related no-start issue. Draining and refueling usually, does the job, remembering to add fuel stabilizer to help prevent a further issue.

These links will help you nail your fueling system diagnosis and repairs –

• ATV won’t start
• ATV smells like gas
• ATV dies when I give it gas
• ATV only runs with throttle
• Why is my ATV running rich?
• Can I ride with choke on?

2 – The engine doesn’t start and critically makes no attempt to fire. This result tells us that you may have an ignition system fault or a compression or timing issue.

Since a lack of spark is the more likely issue, we’ll look at that fault first before checking compression and timing.

Weak Spark

If, after running the Gas shot test, you find you may have a spark issue, then you’ll want to check your spark again. I understand you have a spark but is the spark strong enough? A weak spark is the worst kind to have, as it causes you to discount the ignition system as the root cause of your no-start.

Swap the spark plug for a new or known good one early in the game to help eliminate a possible plug issue.

I advise checking the spark using a spark test tool when ignition system testing. (more on this below)

Before we begin testing, worth knowing what components are in an ignition system and what they do, they are as follows:

Stator – The Stator and rotor create a voltage that feeds the battery and bike electrical systems, including the ignition system. Without a functioning stator, nothing happens.

Pickup coil – Signals the CDI box to fire the spark plug via the coil.

CDI Box – Solid-state unit that’s responsible for controlling and adjusting the ignition timing.

Higher-end, more sophisticated ATVs may employ an ECU instead of a CDI box.

Coil and resistor cap – Coil and cap together convert low voltage into a high voltage which at the critical moment offers a ground path through the spark plug.

Spark plug – The plug is the business end; what began at the Stator ends here. The plug is the least complicated of all the ignition system components.

However, it is the component most likely to cause an issue.

Our mission is to eliminate all the easy stuff first, which means focusing on the spark plug first.

An in-line spark test tool is best as it stresses the whole system and will help locate a failed component that often doesn’t appear in the MacGyver-type spark test.

Check the condition of the spark plug, too; this simple guide will give you a heads-up on what each plug color and condition really mean – ATV plug color guide

Check the plug is correct by checking your manual and check the plug is gapped correctly. Always worth having a spare plug to hand; it’s great for eliminating a plug issue and can save a ton of diagnostic time.

Assuming the plug passes a visual, then I like to try a jump start when I suspect a weak spark. A rotating engine is required to create a spark (about 400 rpm), so a slow-cranking engine may cause a weak spark.

Jump starting scavenges power from an external battery, thereby boosting your ATV battery. Try a boost start, but before jump-starting, check your battery terminals are clean and tight. Loose dirty terminals are a common cause of no-starts.

If you need a jumpstarting refresher, check out this link – How to jumpstart an ATV?

If you find your ATV starts with a jump, suspect a battery issue. Running the following tests will help confirm where the fault lies –

• ATV loose battery terminals
• ATV dirty battery terminals
• ATV battery test

Check also that the battery is charging at idle – Anything over 12.65 indicates it’s charging.

If, on the other hand, a jumpstart made no difference at all, but you feel the spark looks weak, then we’ll need to test the following components –

• Coil
• Stator
• Pickup coil
• CDI Module

You may find these test links helpful:

• Coil and cap test
• Stator test
• Pick-up test
• CDI box fault

You’ll find the tools I recommend, including an inline ignition system test, here on the ATV tools page and common spare parts here on the ATV parts page.

If all checks out OK in your ignition system, then we’ll move on and check your compression.

Compression Checks

Compression is an engine’s ability to squash and maintain the cylinder’s contents inside the combustion chamber. When the contents are packed tightly into the combustion chamber, the spark plug fires and combustion occurs.

However, if compression isn’t built or maintained inside the chamber at the critical moment (past TDC), the mix won’t ignite.

And so, low compression is a possible cause of no-start.

Low Compression Common Causes

There are a ton of causes of low compression; the most serious is engine wear. That is not what any ATV owner wants to hear. However, not all causes of low compression are that serious.

Here’s a list of common causes:

• Engine wear
• Valve wear
• Valve lash adjustment required
• Blown head gasket
• Loose spark plug

How To Check Compression

Checking compression correctly requires a compression test kit, or a leak-down tester may be used to identify compression loss. You can check out the types I recommend on the Amazon links below:

A compression tester gives an exact reading, such as 100 psi. Bear in mind that engine maker compression values vary. Some test good at 100 psi, while others may have a min value of 150 or 200 psi; you’ll need to check your engine spec) this reading is then matched against a workshop manual, where the engine maker will give a min reading.

It’s common to run a dry compression test first and then a wet test; comparing the different results helps identify the root cause.

Compression test as follows:

• Remove spark plug
• Ground coil
• Fit compression tester
• Choke off
• Throttle wide open
• Crank over 6 – 10 times
• Read and note the highest reading

The wet test is the same but with oil in the cylinder.

The results of the Dry and Wet tests are interpreted as follows:

Both dry and wet readings are the same – Probable that you are facing an issue with the engine’s top end.

Readings are different, and compression is low – Probable your engine is experiencing issues with worn rings, pistons, cylinders, or a combination of all three.

Readings are the same, and compression is normal – Low compression is not the cause of your issue. At this point, we’ll go ahead and check the engine timing.

A leak-down test, in many ways, is more useful. It involves filling the cylinder with compressed air and using a test tool to measure the cylinder’s ability to hold pressure over a given period.

The added bonus of this test kit is it simultaneously points to the area at fault. In a problem engine, the compressed air will be heard to leak from the cylinder.

Diagnosis as follows, air leaking from:

• Oil cap or dipstick – worn piston rings : (
• From muffler – Exhaust valve issue (worn seat or may just need adjustment)
• From carburetor /air box – Intake valve issue (worn seat or may just need adjustment)
• Between cylinder head and block – Head gasket failure

You may find the following links helpful –

• ATV valve adjustment in 6 steps
• ATV valve adjustment symptoms
• ATV coolant in cylinder
• ATV coolant in oil

Testing Compression MacGyver Style

What if you don’t have either test kit to hand? We can try the MacGyver compression test kit. It involves our thumb and a rubber glove…..It’s not what you think.

This test method isn’t scientific or very accurate; it’s loosely accurate, a blunt tool if you like, but it does hold some value.

Test as follows:

• Remove spark plug
• Ground plug against cylinder head or use a jumper cable to remotely ground. An un-grounded coil wire will give you a jolt and is also bad for the ignition system.
• Place your thumb over the open plug hole (important to wear a rubber glove)
• Have helper crank engine

Two results are likely:

1. You’ve got some compression – You feel the effects of good compression on your thumb (vacuum and then propulsion)

2. You have no compression – You feel the effects of a lack of compression as your thumb will feel a mild or no effect of vacuum and propulsion as the engine is cranked over.

A lack of compression will likely require the aforementioned leak-down test kit to diagnose the root cause.

Timing Issue

If all checks out so far, or at least as best you can tell, then there’s one more item we can check – Engine timing. The engine, as you know, is like a watch, the internal parts all play a part, and they each have their moment to shine. When timing is off, it means some of the internal components are doing their thing too early or too late, usually the latter.

There are three components that must be timed in relation to each other correctly for an engine to run at its best:

1. Engine pick up – Is a sensor that signals the CDI to remove coil ground and fire spark plug
2. Crankshaft TDC (Top Dead Center) – Is a marked point on the crankshaft that provides a signal maker for the engine pick-up sensor
3. Camshaft – Responsible for valve train control and is timed to the crankshaft, usually by the timing chain. (some engines employ geared cam, which means the valves are controlled by pushrods)

So how can you tell if the timing is off? There are two common ways to go about this; if an engine is running and the mechanic suspects the timing is out a little, then a timing light is used.

However, if, as in our case, the engine is a nonrunner, we’ll need to go ahead and remove some covers and check timing marks on both the crankshaft and the camshaft.

Ignition Timing

Timing light – For engines that are out of time by a little but still running, a timing light may be used. It’s a strobe light tool that’s connected to the plug wire, which causes the strobe light to operate intermittently. The timing light is then shone on the engine timing marks allowing for easy checking. This, of course, checks the ignition timing only, not the crankshaft to camshaft timing.

Crankshaft to Camshaft Timing

The less technical way is to just go ahead and remove some covers and rotate the engine by hand to check where the timing marks line up.

It involves removing some engine covers to check the crankshaft and camshaft gear/sprocket markings. It’s not difficult, just a little tedious.

For ATVs with pull starters, you may need to remove the pull assembly to access the timing window.

All engines are slightly different, but this is a pretty typical setup.

The process is as follows:

• Access the crankshaft timing window, as seen in the above picture.
• Remove the spark plug.
• Crank the engine over by turning the crankshaft counterclockwise with a socket and wrench.
• When the rotating mark (T) aligns with the engine cover mark (I), the engine is set to TDC.

But we are not finished yet; now we need to make sure the camshaft is in the correct position, and to do that, we’ll need to access the cam gear.

The process is as follows:

• Locate the cam gear
• Remove inspection cover
• Check the cam sprocket mark aligns with the cylinder head mark

How does the timing go out?

Three reasons are common:

1. Jumped time – Timing sprocket, tensioner, and guides wear; they allow the chain to slip a tooth or two.
2. Rebuild error – Error made when refitting the timing chain.
3. Stretched chain – As chains wear, they stretch, and this causes the relationship between the crank and cam to change.

You may find this post helpful – How to tell ATV jumped time?

A comprehensive ATV no-start guide that will get you rolling in jig time.

ATV no-start guide

You may find the following posts helpful:

• Air cooled ATV white smoke
• How to tell if ATV fuel pump is bad
• How to tell ATV jumped time
• Will ATV start with bad stator?
• How to jumpstart an ATV?
• ATV coolant in cylinder
• ATV coolant in oil

I’ve written a ton of ATV troubleshooting posts. Hopefully, you won’t need them, but if you do, we have you covered.

ATV Troubleshooting Guides

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

• ATV Rear Brake Pedal Stuck - Solved!
• How to Tell ATV Fuel Pump is Bad? This is how ...
• Will Dirt Bike Start If Timing Off? Run this test

The post ATV Has Spark and Fuel But Won’t Start – Fixed! appeared first on ATVFixed.com.

Engine timing is mission-critical. Getting this stuff wrong can spell big trouble. If you suspect the timing is out, best not to run the motor.

Checking ATV engine camshaft and crankshaft timing marks is the correct way to verify timing. It’s a simple 4 step process:

1. Remove spark plug
2. Remove camshaft cover
3. Set engine to TDC on compression stroke
4. Check camshaft sprocket marks align correctly

By the end of this post, you’ll understand clearly how to check your ATV engine timing marks, why timing jumps and how to fix it, and also other causes of bad timing.

Timing

Timing is everything, every component of your engine has an important job to do, and some components have to do it at a very precise moment in the engine cycle. Doing their job too early or too late can make the difference between an engine on full song and no singing at all.

The bottom end of your engine (crankshaft) coordinates with the top end (valve train). It employs sprockets, chains, tensioners, and guide rails to keep everything in time. The valves positioned in the cylinder head open and close sequentially, allowing fuel in and spent gases out.

This is if you like the mechanical coordination or timing of the bottom of the engine (crankshaft) with the top of the engine (camshaft).

But we must also consider the electrical coordination or ignition timing, meaning when the spark plug actually creates a spark. The spark plug as you know, needs to fire at the correct time. Ordinarily, when the engine is idling, the plug fires when the engine is at TDC, and it signifies the beginning of the power stroke.

As the engine speeds up, though, the plug is fired earlier (known as BTDC (Before Top Dead Center)); this is because the spark plug takes time to produce a spark. Starting the process early, therefore, means the plug continues to fire at the sweet spot in the engine cycle.

The firing, advancing, and retarding of the spark plug is controlled by the trigger (aka pulse, pickup, or crankshaft sensor (CKP)) and the CDI box (Capacitor Discharge Ignition).

Ignition timing is automated by the CDI box; that said, an ignition timing issue may be caused by a faulty CDI box or an incorrectly positioned pickup sensor.

Timing a 2-stroke engine is a ton easier than timing a 4-stroke motor because 2-strokes don’t have a camshaft, and so crank-to-cam timing doesn’t exist. Only ignition timing is important. I wrote a post about adjusting the ignition timing on a 2-stroke engine, and you can check that out here – Check and adjusting 2-stroke timing

Your ATV engine is a four-stroke engine so called because it has four clearly defined operational stages.

The piston moves down the cylinder and draws fuel mix in through the open intake valve.

The piston moves up the cylinder, compressing the air-fuel mix (valves closed).

Plug fires, and the piston moves down the cylinder powering the crankshaft (valves closed).

The piston moves back up the cylinder, forcing spent gases out of the open exhaust valve.

And the cycle starts over.

Symptoms of Bad Timing

There may be lots of reasons why your ATV engine doesn’t sound or operate like normal. Timing is not usually one of the first items checked unless it suffers from some of the following symptoms:

• No power
• Popping in the carburetor
• Backfiring
• No start
• Engine binding on crank
• Poor idle
• Long crank
• Won’t rev
• Hot starting issues

Don’t rule out some of the simple causes first, and they include the following:

• Fouled spark plug
• Wrong plug type
• Bad gas (a common cause of issues)
• Valve lash needs adjusting
• Faulty coil or cap
• Faulty or misaligned pickup
• Faulty stator
• Faulty CDI
• Flywheel magnet position fault
• Sheared flywheel key or missing

For a comprehensive ATV no-start post with stepped illustrations, check out – ATV won’t start

Checking Timing

Checking your timing is a straightforward procedure, but you’ll likely need to remove a few items to gain access. This guide guesses that your engine is an Over Head Cam found in most modern ATVs. I’ve included a single and a twin cam; your timing markings will likely be different, but not to worry, from the timing diagrams below, you’ll get the picture.

The process goes like this:

Step 1

• Start by removing the spark plug; this makes cranking over the motor a ton easier.
• Locate and remove the timing inspection hole.

Step 2

• Rotate the flywheel counter-clockwise slowly using a suitable socket and ratchet. The timing mark “T” or equivalent will appear in the inspection window. This indicates Top Dead Center (TDC)

• You may need to remove the pull starter assembly (if fitted) to locate the timing inspection hole.

Step 3

• Go ahead and remove the camshaft inspection cover or remove the cam cover.

• This is a single-cam engine with the crankshaft set to TDC.
• Go ahead now and check your marks on the cam timing sprocket. It should align with the mark on the cylinder head.

For twin-cam engines, the process is similar, with just an extra sprocket mark to line up. Typically, both sprocket marks align with the horizon plain of the cylinder head (marked as red lines below), and some sprockets may have an additional mark (not in the pic below), and typically they point straight upwards (90°).

Step 4

• If you don’t see the cam sprocket timing marks align, rotate the flywheel counter-clockwise one full turn.
• Position the “T” or equivalent TDC crankshaft mark in the inspection window once again.
• The sprocket mark(s) should now be aligned on the head (horizon plain of the cylinder head, (Twin-cam)) and the additional cam marks pointing upwards 90° (if applicable). The engine is now set to TDC on the compression stroke.
• If all cam timing marks don’t align, your timing is out and will need to be reset.

But Why is the Timing Out?

The timing chain and valve train are mechanical, the timing chain, guide rails, and chain tensioner drive the valve train, and they just wear out, and valves require adjustment for trouble-free service.

The symptoms of maladjusted valves vary; I wrote a post about it which you may find helpful – ATV valve adjustment symptoms

I also wrote a post about adjusting the valves, which you may find useful – ATV valve adjusting in 6 steps

The more usual causes of jumped timing include:

• Worn or faulty hydraulic chain tensioner
• Worn timing chain
• Worn sprockets
• Worn chain guide rails
• Stretched chain
• Low oil level
• Poor quality oil
• Sheared flywheel key
• Over revving engine

Resetting Timing

Resetting the timing can be a pain in the ass, but you do need to get it correct. If the timing isn’t correct, the piston could impact the valves, causing some very expensive repairs. Your very first job is to find a manual for your engine. The process, torque specs, and tightening sequences vary from engine to engine.

Critical information and tools

You’ll need to know your timing marks, torque specs, and fastener sequences, and you’ll need a torque wrench. You’ll find a list of all the tools I use here on the ATV tools page.

This guide will give you a general flavor of the job ahead.

• Remove the cam covers and set the crank and cam sprockets to TDC on the compression stroke.
• Remove the tensioner
• Remove the chain from the top of the sprocket(s) and hold
• Realign the sprocket(s)
• Refit the chain
• Reload the tensioner – screw-back to reload
• Fit tensioner plus new gasket and torque to spec
• Fire the tensioner by tapping, usually.
• Check timing marks
• Rotate the flywheel counter-clockwise, two full turns, and check the timing again.

A full inspection of the chain, sprockets, guides, and tensioner is advised. A failing tensioner is a very common cause of jumped timing, and obviously, if root causes aren’t fixed, timing will jump again and maybe with costly consequences.

You may find these posts useful:

• How often to service an ATV?
• ATV parts page
• ATV won’t jumpstart
• Air-cooled ATV white smoke
• Will ATV start with a bad stator?

A comprehensive ATV no-start guide that will get you rolling in jig time.

ATV no-start guide

I’ve written a ton of ATV troubleshooting posts. Hopefully, you won’t need them, but if you do, we have you covered.

ATV Troubleshooting Guides

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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The post How To Tell ATV Jumped Time? (In 4 Steps) appeared first on ATVFixed.com.

Electrical gremlins can be challenging to tame, but you’re in the right place.

An ATV will not start with a bad stator. The engine requires an electrical current from the stator to power the coil and fire the spark plug. Symptoms of a faulty stator may include:

• No start
• Intermittent start
• Misfiring
• Hot start issues
• Backfiring
• Fouling plugs
• Flat battery

In this post, you’ll learn how a faulty stator also known as an AC Magneto affects your ATV, how to test it, and how to replace it.

It is possible for the engine to start if the stator is failing. However, it all depends on how it’s failing. An intermittent failing stator will cause the engine to run like a pig or not at all.

An inconsistent voltage supplied to the coil will result in:

• Misfiring plug
• Black smoke
• Fouling plug
• Hesitation
• Stalling
• Backfiring

You get the idea!

What Does A Stator Power?

There are two flavors of stator, single or 3 phases. The 3 phases are the most common. Each phase of the stator is comprised of copper wire wound around an iron core. The stator is fixed to the engine, and as the rotor (some may call it a flywheel) with magnets attached rotates around the coils, voltage is created.

All engines need electrical current in order to function. Even a basic ATV without lights, battery, or starter motor still needs voltage to power the coil. The coil as you know transforms voltage into a spark at the plug.

More sophisticated ATVs will have larger demands – ECU, battery, starter motor, electric steering, dash lights, sensors, coolant fan, lights, winch, etc.

While your ATV may have a battery, all voltage is ultimately provided by the stator. On most ATVs, battery power is used to operate dash lights and crank over the engine.

The stator does all the heavy lifting. The cranking rotor excites the stator which generates voltage to power the coil via the CDI box (Capacitor Discharge Ignition) or ECU (Engine Control Unit), whichever your ATV has.

After the engine starts, the stator provides all the power required, including topping up the battery voltage spent cranking the engine over. And so you can see how important a working stator is, that said let’s get down to checking yours.

Some bikes run a basic CDI system and more sophisticated fuel-injected bikes will have an ECU.

Obviously, wiring is model-specific, but the diagrams here give you a feel for the importance of the stator.

How To Test The Stator

Stators do a very important job and are under a ton of stress, so you won’t be surprised to learn they fail all the time.

Common stator problems:

• Open circuits
• Shorts
• Damaged or corroded wiring
• Power-washing – over doing it with the power washing is a common root cause of problems, it forces water in and can short out circuitry or cause corrosion
• Rotor fault – magnets falling off is popular with some brands
• Wiring loom – rodent damage
• Block connectors – loose/corroded block connectors

Three stator tests are common:

1. Dynamic Battery Voltage Test (engine running)
2. A Static Resistance Test (engine off)
3. A Dynamic Voltage Test (with engine running)

1 Dynamic Battery Voltage Test

This test is called dynamic meaning your engine will be running. This is the easiest and fastest stator test of all, that said, it’s not conclusive. This test won’t suit if your engine isn’t running, if that’s the case, go ahead and move to the static resistance test below. You’ll need a voltmeter, a helper would be great and you’ll likely need to remove your ATV seat to gain access to the battery.

You’ll find the tools I recommend including a Voltmeter here on the ATV tools page and you’ll find common spare parts here on the ATV parts page.

The process is as follows:

• Start your engine.
• Have helper hold throttle at approx 3000 rpm.
• Connect voltmeter as per picture below Red probe to + battery terminal and black probe to – battery terminal.

A healthy charging system will read 13-15.5 volts. This ATV is charging while not quite 13 volts, it’s working OK.

If you have a reading between 12 and 12.65-volt range, your charging system isn’t working and the stator may indeed be at fault. But it isn’t the only possible cause. Here are a few of the more common causes of a no charging issue:

• Loose battery terminals
• Dirty battery terminals
• Faulty battery
• A blown fuse
• Loose wiring
• Faulty Rectifier / regulator
• Faulty stator

2 Static Resistance Test

The tests called static means your engine and ignition switch are off. This test will suit you if your bike won’t start and you’ve checked for spark at the plug and found nothing, or you found your bike isn’t charging and you have checked all the low-hanging fruit like loose battery terminals, etc.

For this test, you’ll need a voltmeter (DVOM), and you’ll need to access the stator wiring loom.

It’s easy to locate, as it’s the loom that exits the engine side cover.

You will need to follow the loom to a block connector and you’ll need to disconnect it, yours may be further back towards the rear of the ATV, but you get the idea.

You’ll be testing the stator/engine loom side, and as your engine probably isn’t running, we’ll perform the static test first.

This is a two-part test, and both tests are simple to execute. I’ll assume you have located and disconnected the stator terminal. The block terminal connector may contain three wires or more.

You’ll be looking for three identical wires or three wires grouped.

Some terminals will house just the stator wiring in the terminal, and others will integrate the pickup wiring. I’ve included both in the picture.

Let’s name the three stator terminals A, B, and C; the designation and order is unimportant. You should know that we only ever test resistance on a dead circuit, meaning the terminal must be disconnected. Attempting to test resistance on a live circuit may damage the voltmeter or the circuit.

• Set the DVOM to read resistance (Ω) may also be written as “ohms”.
• Using your meter, read resistance between A and B, B and C, and finally, A and C.

The reading should be in the region of .1 to 1 ohm. Each manufacturer will have its own spec. But as a rule of thumb, resistance should be low and should not read open.

An open (O/L) meter reading on one phase is the most common result when testing a faulty stator.

Testing short to ground

This is the second part of the static test. Attempting to test resistance on a live circuit may damage the voltmeter or the circuit.

• Place the ground probe on chassis ground
• Probe A, B, and C, in turn
• All should read open circuit

Any reading on the meter other than an open means you have a short to ground which means your stator is faulty and will need to be changed.

3 Dynamic AC Voltage Test

The dynamic test will require a running engine and so may not suit all readers. Note the reading of voltage in this test is AC (Alternating Current), not the more common DC.

• Set your meter to read AC voltage (~) and the engine running
• Probe A to B; A to C; B to C

A reading of 15 to 60 volts AC can be expected, crucially the voltage should not be less and should rise with RPM.

Fitting Stator

Fitting a stator is straightforward, but you’ll need a special crankshaft rotor tool, and it may be engine-specific.

To replace the stator:

• Remove side cover – may need to remove gear selector footrest, etc
• Remove the side cover – unfasten bolts in a star pattern to avoid straining the cover
• Loosen rotor nut – may need a rotor holding tool

• Using rotor wheel puller, pull rotor
• Remove nut and remove rotor – be mindful of Woodruff key
• Remove the stator fasteners & remove stator

Refitting

Align the rotor key-way with the crankshaft key and torque to specification. (You’ll need to use the rotor holding tool and you’ll need a torque wrench tool). Incorrect torque can cause the rotor to come loose, or over-tightening can crack the rotor.

The crankshaft is a super important component, over-tightening can damage it so please do get the correct torque spec and use a torque wrench.

Ensure the wiring isn’t pinched by side cover and the grommet fits correctly. Replace the side cover gasket and torque to spec and in a star sequence.

You may find the following posts useful:

How do kill switches work?

Will bike start without kill switch?

Ok to pressure wash an ATV?

ATV won’t start after washing

• About the Author
• Latest Posts

John Cunningham

John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.

www.atvfixed.com/about-john-cunningham/

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• Will Dirt Bike Start If Timing Off? Run this test

The post Will ATV Start With Bad Stator? (3 Simple tests) appeared first on ATVFixed.com.