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How to Adjust Carburetor Floats on ATVs

by Troy Lambert; Updated October 25, 2017

Items you will need

  • Phillips screwdriver

  • Small drain pan

  • Impact driver

  • Small hammer

  • Float gauge

  • Small flat-head screwdriver

Adjusting the carburetor float on an ATV is a necessary step in the process of rebuilding or rejetting the carburetor. Each time the carburetor is removed from the ATV, the float level should be checked for adjustment, and reset if necessary. There are two methods, and a few simple steps to adjusting the floats on an ATV carburetor.

Shut off the fuel delivery switch, and remove the carburetor. Typically there will be two clamps holding the carburetor in place, one on a boot to the intake (motor side), the other to the air box. Using a long Phillips screwdriver, loosen these clamps, and then slide the carburetor out of each. Detach the accelerator cable. Check your manual for instructions on how to do this, as there are a variety of ways the cable attaches to the carburetor. Set the carburetor in a clean and well-ventilated work area.

Inside a small drain pan, turn the carburetor upside down. Some fuel will drain from the carburetor. Set the drain pan aside. Carefully remove the float bowl. There are usually four screws attaching the float bowl to the carburetor. Using the Phillips screwdriver, remove the four screws. If they do not want to turn, do not force them. They are usually brass or a similar soft metal and will strip easily. Instead, use an impact driver with a Phillips bit. With one hand hold the carburetor and hold the impact driver in place. Gently tap the top of the impact driver with a small hammer. Usually a few sharp taps with the hammer will get the screws moving. Once the screws have been removed, set the float bowl to the side.

Consult your manual for the proper float height for your carburetor, typically in the 17- to 19-mm range. Hold the carburetor sideways at a 90 degree angle with the float pointing downward from its hinging or pivot point so it moves freely when the carburetor is tilted gently from side to side. Tilt the carburetor upward till the float stops moving, or "seats." Check the float height using the float gauge. It should be within 1 mm of the factory specification. There is a small metal "tang" in the center of the float assembly that bends easily. If the floats do not fall within specification, use the small flathead screwdriver to bend the tang and retest. Continue this process till the float is within specifications.

Reattach the float bowl to the carburetor. Check the bowl gasket to be sure it is seats properly and will not leak. Attach the accelerator cable, and reinstall the carburetor on the ATV. Turn on the fuel selector valve, and inspect for leaks. If none are found take the ATV for a test ride, then reinspect.

Tips

If you do not have the specifications for your ATV, you can approximate. Hold the carburetor as described in step 3 and follow the same process, with the exception that the float should be approximately 90 degrees to its pivot point when it seats. Note that this is an approximate measurement only, and that the best performance from your carburetor will be achieved when the float height is in the exact specified range.

Warnings

When working with fuel, always work in a well ventilated area away from spark or flame. Fuel may also be a skin irritant, so where neoprene gloves when possible. If skin or eye contact does occur, flush immediately with water, and if irritation persists, contact a medical professional.

About the Author

Based in North Idaho, Troy Lambert has been writing how-to pieces and historical articles for magazines such as "Woodworking" and "Outdoor Idaho" since 1994. Lambert is also a novelist and has a diverse technical and philosophical education. He holds a technical certification from the Motorcycle Mechanics Institute in Phoenix.

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