Are ATV Gas Caps Universal?

Losing a gas cap is easy to do, finding it however, especially when your off-roading is next to an impossible task, but hey, we’ve all done it!

ATV gas caps are not universal, while some caps may be interchangeable, it is advisable to get a proper fitting gas cap. Poor fitting gas caps can cause carburetor issues.

In this post you’ll learn why a proper fitting gas cap is an important safety issue. You’ll also learn how a bad gas cap can cause irritating engine performance issues.

Gas Cap Types

The most common types of ATV gas cap are screw type and 1/4 turn caps. The screw type are generally superior quality, better fit and last longer. Caps are commonly made from plastic with the higher end caps made from billet alloy.

Billet alloy is as good as it gets for ATV gas caps and can cost anywhere from thirty to eighty dollars. The alloy is hard wearing and resists corrosion.

The 1/4 turn cap is generally not as well made, it wears and becomes loose. A worn or ill fitting cap allows gas vapors escape and gas splash.

All good quality ATV gas caps are fitted with a vent valve and pipe.

Gas Cap Safety

You already know gas splash caused by a loose cap is dangerous, but even escaping gas vapors can be lethal. After all your gas tank is fitted right above the hot exhaust pipe and while accidents are rare, it can happen.

Poor Engine Performance & Bad Gas Caps

You wouldn’t think a bad gas cap could cause intermittent engine problems, but it’s so common. When you lose a gas cap, it’s understandable to try and improvise with an old plastic cap that seems to fit. But that’s usually where the problem starts.

An ATV gas tank needs to inhale, most ATV fuel systems are gravity feed. As the fuel leaves the gas tank, it’s replaced with air. If the tank is sealed, gas flow eventually slows to a trickle or a complete stop. That’s why ATV gas caps are fitted with an air vent valve and pipe.

Typical symptoms of a blocked gas cap valve include:

  • Engine starts then stops after a while
  • Engine stalls
  • Engine just lacks power
  • Engine won’t rev

But a bad gas cap can also cause excessive moisture in the gas tank, and allows the gas to evaporate. This eventually leads to a build up of water in the tank which makes its way to the carburetor, and that means your ATV is out of action.

A regularly used machine will have no problem burning off a little moisture in the gas, but an ATV’s that spend a ton of time sat up will likely suffer from gumming of the carburetor.

Gas Stabilizer Prevents Gumming

Gumming is a sticky deposit that clogs up the fuel system and can be expensive to repair. It’s a carburetor killer, but totally preventable.

So why does gumming of the carburetor happen? It’s basically caused by old gas and when I say old I mean anything older than one month. Yep, gas is well on it’s way to being stale after just one month.

Modern gas is a blend of regular gas and ethanol, and it’s the ethanol that’s causing the problems. The alcohol in the gas attracts moisture and when the ATV is left sitting idle, the gas turns to a sticky mess known as gum.

Stale gas is the number one cause of ATV problems in my workshop. The fix is drain the old gas, clean the carburetor and replace the gas filter.

However all this expense could be avoided. Obviously a good gas cap that allows the tank to inhale but prevents gas evaporation helps, but the sure fix is a fuel stabilizer.

The stabilizer which is a fuel additive can be bought at auto parts store and is simply mixed with the gas. Stabilizer will keep your gas fresh for up-to two years.

You only need to use it if you intend parking up your ATV for more than one month. When mixing the additive you’ll have to run the engine long enough to get it mixed through out the gas system. I’ve used this stuff for years and never had a problem with gumming.

Related Questions

ATV gas cap is frozen? Using a kettle of warm water (not boiling), pour some around the neck of the tank. Using a gloved hand remove the cap. Spaying some Teflon coating or some non stick frying oil on the cap and neck will help prevent freezing.

John Cunningham

John Cunningham is an certified mechanic and writer on 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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