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


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

Starting an ATV in cold weather will require fuel enrichment. Some ATV’s 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. Looks complicated but it’s not, it just means for every 14.7 parts 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 the purpose of this post we’ll deal with the far more common and problematic, carburetor models.

The AFR of 14.7:1 is known as stoichiometric, its basically the optimum ratio of oxygen to gas. It is however a delicate balance, and many variables can throw if 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 causes problem starting because cold air is oxygen rich, and that means your engine is receiving more air proportionally than gas.

This is know as a lean condition and it causes starting and stalling or no starting 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 type thermo sensor and mechanical assembly to control 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 direct 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, disadvantage with this style is it must be turned off again.

Start ATV In Cold

Obviously 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 it your bike is a manual or auto choke.

A manual choke will be positioned on the handle bars or at the carburetor it self.

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 drivers 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 may be auto choke, lucky you!

If your bike is auto choke, to start it simply:

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

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

To start an 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 bike warms up.

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

Hiccupping and popping means it still needs a little choke.

Extreme Cold

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

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

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

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

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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