ATV Carburetor Troubleshooting

by Justin Mitchell
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atv airborne image by MAXFX from

When you are having trouble with your ATV, oftentimes the carburetor can be the secret culprit. A host of things can go wrong with it, but there is no need to be frustrated. There are several basic troubleshooting tactics you can use to figure out what the problem is without wasting money or unnecessary trips to the garage.


A carburetor is the section in a vehicle's engine where the fuel is transformed into a vapor and mixed with air in order to be ignited in the vehicle cylinders.

Basic Troubleshooting Tips

If your engine is running roughly and/or idling harshly, it probably means there's some dirt clogging the carburetor. The biggest problem with fixing this problem will be getting to the carburetor, which is often buried quite deeply in the engine.

If the carburetor is badly clogged, you might have to disassemble it and clean it. This is not difficult, requiring only basic mechanic skills. The most important thing to remember is to keep track of where each part goes, making a chart if necessary. You will need a specialized carburetor cleaner to do this task.

You can take off the float bowl without taking apart the entire carburetor. It is usually the problem with a harsh idle, if the problem was not tracked to another part of the vehicle. Clean the bowl with carburetor cleaner and a toothbrush. Clean the main and slow jets as well. Before you reconnect the bowl, check the bowl gasket to ensure it isn't damaged. This can be the cause of several different problems.

Adjusting the Carburetor

Most problems with carburetors involve improper adjustment. Learning how to put a carburetor into the proper adjustment is the best troubleshooting tactic.

There is an ideal mixture between fuel and air that your car engine needs in order to run at maximum efficiency. The problems with your carburetor and, therefore, your engine could be a result of this mixture being off. To find out if the mixture is optimum, find the point at which your engine revs at peak efficiency. If there is too much air, it slows down. If there is too little, it also slows down. Somewhere in the middle, it will run the fastest.

There should be a screw on the side of the ATV's carburetor. The farther the screw is screwed outwards, the more air is being allowed into the engine. With the engine off, turn the screw until it seats, and count how many turns this takes. This will be your return in case your adjustments don't work. Then turn the screw back to the baseline adjustment.

Start the engine. With the engine running, turn the screw in, or clockwise. Make 1/4 turns until you notice the engine speed drop. Then turn it counterclockwise until the speed goes back up. Work for a while until you feel you've found the "sweet spot."

If you turn the screw all the way, and the revs keep increasing, then you need a different-sized pilot jet for your engine. If you screw it all the way in, and the revs keep going up, you need a bigger one. If you've screwed it all the way out and they still have not peaked, you need a smaller one.

If this process has no effect, then your carburetor is probably blocked with dirt from either the air filter at the mouth of the carburetor or the pilot jet is blocked with dirt. Check both of them.

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