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:
- Too much engine oil
- Pull starter assembly fault
- Ignition system fault
- Fuel system fault
- 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.
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.
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.
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.
- Fuel – They need an air/fuel mix to the correct ratio
- Spark – They need a strong spark fired at the correct time
- 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?”
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.
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