How To Start ATV In Cold Weather (Brrr starting tips)


When the temperatures drop, ATVs can struggle to start. There’s a good reason for that, and the fix is usually simple.

Starting an ATV in cold weather will require fuel enrichment. Some ATVs do this automatically. Others use a manual choke lever or fuel primer. To start an ATV with manual choke type:

  1. Apply Choke lever
  2. Don’t apply throttle
  3. Crank over engine

In this post, you’ll learn how to start your ATV in cold weather, why it struggles when the temperatures drop, and you’ll also learn the common problems and fixes with ATV engines as the temperatures drop.

Air Fuel Ratio (AFR)

I’m not going to get deep in the weeds here, so stay with me. Many of you will already know this stuff anyway. But it is helpful to understand why your ATV struggles to start in colder weather.

It’s all about the air to fuel ratio. Your ATV engine likes an AFR of 14.7:1. It looks complicated, but it’s not. It just means for every 14.7 parts of air (oxygen) your engine gets. It also needs to get one part gas.

Simple enough so far, right?

Some modern bikes use a closed-loop computer-controlled fuel system and while the destination is the same, how they get there differs from the more common and problematic carburetor models.

For this post, we’ll deal with the far more common and problematic carburetor models.

The AFR of 14.7:1 is known as stoichiometric. It is the optimum ratio of oxygen to gas. It is, however, a delicate balance, and many variables can throw it off. You’ll experience this as poor performance or hard starting, and the list of symptoms goes on and on.

The AFR needs to be adjusted for cold-weather riding and at higher altitudes, humidity, or after modifications to your engine.

Cold Weather Starting

Colder temperatures cause problems starting because cold air is oxygen-rich, and that means your engine is receiving more air proportionally than gas.

This is known as a lean condition, and it causes starting and stalling or no start at all. You’ll often find a bike will be easier to start at mid-day simply the air is warmer and less oxygen-rich.

Computer-controlled bikes, of course, are programmed to read the temperature and add more gas, so the ratio is closer to stoichiometric.

Carburetor bikes aren’t that clever, and so the rider needs to make a manual adjustment using the choke lever or primer.

Choke Types

Choke types vary. The most common types are auto choke, primer, and choke plate.

Auto choke – is, well, automatic, and so you needn’t concern yourself with it unless your bike won’t start. Most Auto chokes use some Thermo sensor and mechanical assembly to control the choke.

Primer – the primer is the simplest of all to use, and lots of small engines mower chainsaws use them. A priming bulb is pressed, and it injects extra gas directly into the carburetor. This helps counteract the lean condition caused by the oxygen-rich cold air.

Lever choke – this type is a simple lever that restricts air supply to the engine. This has the same effect as adding more gas – it adjusts the ratio closer to stoichiometric. The disadvantage with this style is it must be turned off again.

Start ATV In Cold

It’s best to keep your ATV indoors, and that will help the starting process and be a lot easier on your bike long term.

First off, go ahead and determine if your bike is a manual or auto choke.

A manual choke will be positioned on the handlebars or at the carburetor itself.

It will be accessible. You won’t need to remove any covers or panels to access it. You may need to dismount to locate it, however, but it will be accessible from the driver’s seat, usually on the left-hand side below the gas tank.

The choke lever or button may be marked “Choke” or have the choke symbol, which resembles a letter “N” or “Z,” depending on how you view it.

If you failed to find the choke lever, your bike might be an auto choke, lucky you!

If your bike is auto choke, to start it:

  • Turn ignition on
  • Select neutral
  • Slide kill switch to “On”
  • Pull clutch (some bikes)
  • Hit start button

Don’t apply any throttle until the bike warms up. Wait 1 – 5 minutes, depending on conditions.

To start a manual choke bike:

  1. Turn ignition on
  2. Select neutral
  3. Pull choke to full or pump primer bulb 4-5 times
  4. Slide kill switch to “On”
  5. Pull clutch (some bikes)
  6. Hit start button

Don’t apply throttle until the bike warms up.

After the start, move to choke back to 1/2 and, after a minute or so, turn to choke off. Timing is really determined by how the bike is running.

Hiccupping and popping mean it still needs a little choke.

Extreme Cold

I lived and worked in Canada for a few years and have had some small experiences of extreme cold temperatures. If we’re talking Brrr temps here, you’ll need to borrow a hairdryer or a heat gun.

Start by warming the carburetor area for a few minutes (without damaging any plastic/rubber components), then direct the hot hairdryer air into the intake duct, may need to remove the seat.

Now attempt to start the bike as above, keep the dryer on the air intake until she warms.

Living in these kinds of temperatures takes a special kind of tough, both human and machine. A block heater for your bike is an easy mod that will pay off big-time every winter.

You may also find the following posts useful:

Can I ride with choke on?

Bike dies when choke is off

Bike dies when I give it gas

John Cunningham

John Cunningham is an certified mechanic and writer on ATVFixed.com. I’ve been a mechanic for over twenty years, I use my knowledge and experience to write articles that help fellow gear-heads with all aspects of ATV ownership, from maintenance, repair to troubleshooting.

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