Air Cooled ATV White Smoke (This will fix it!)


White smoke from the tailpipe looks serious, but usually, it’s a simple problem, easily fixed.

Top 4 reasons for white smoke from an air-cooled ATV include:

  1. Too much oil
  2. Wrong oil type
  3. Contaminated gas
  4. Condensation

By the end of this post, you’ll understand the root causes of white smoke from an air-cooled ATV and what you can do to fix them.

1 Too Much Oil

Mixing gas and oil is mission-critical to a two-stroke engine. As you know, a two-stroke doesn’t have a sump filled with oil; instead, the engine depends on the two-cycle oil to lubricate and cool the moving parts.

Without the oil, the engine would seize solid within minutes. Too little oil in the gas mix risks seizure also.

Being over-generous with the oil is bad too. It causes the motor to run lean, and a lean engine runs fast and hot.

In addition, excess oil accumulates in the crankcase and is eventually burnt in the combustion chamber, where it causes a ton of white smoke.

Your carburetor is calibrated (jetted) to burn oil and fuel to a specified ratio, for example, 32:1. Deviating from this very precise ratio can cause your engine to run lean or rich. Both will shorten the life of your engine.

2 Wrong Oil Type

Using the wrong type of oil is a common mistake. Regular engine oil is too heavy for burning in a two-stroke engine and will produce plooms of white smoke.

Engine oil won’t protect your engine either. It doesn’t thoroughly mix with gas, and your engine will be damaged by friction and heat. Even a short period of operation could cause damage.

3 Contaminated Gas

Bad gas will cause any engine to act up. Regular gas goes stale after three months and blended gas after just one month.

Blended gas

Fuels with higher alcohol content generally aren’t good for two-stroke engines. Ethanol blended fuels like E15 burn hotter, and heat is the enemy of any motor. Regular gas is preferred.

Water

Riding through water will cause steam on the exhaust, and if the airbox gets a drink, the engine will ingest it and turn it into steam.

So, if you’ve been playing in the water, check that airbox, its drains, and air filter. Drain the carburetor gas bowl too.

Not Gas

Accidentally and unknowingly filling the gas tank with diesel, white spirits, thinners, or I’ve even had to drain wine/vinegar from a gas tank.

Accidents happen, especially when gas refill cans aren’t clearly marked.

If you suspect gas contamination, you’ll need to drain the tank, carburetor bowl, and fit a new inline filter.

4 Condensation

Those from a warmer climate may not be familiar with white smoke at startup. It’s part of motoring life in colder climates. The exhaust pipe gases create condensation as it meets the cold ambient air.

As the engine warms up, the white smoke increases in opacity and reduces in quantity.

If this sounds like your symptom, you’ve got nothing to worry about.

You may find these posts useful:

ATV coolant in the cylinder

ATV coolant in the oil

How to tell ATV jumped time?

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John Cunningham

John Cunningham is a certified mechanic and writer on ATVFixed.com. I’ve been a mechanic for over twenty-five 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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