Gone Outdoors

How to Rebuild a Motorcycle Carb

by William Machin

Most motorcycle carburetors on two-stroke and four-stroke engines are not complex pieces of equipment. The gasoline level in the fuel bowl is controlled by the fuel float. Intake air flows through a filter and forces gasoline from the bowl through small jets. The fuel-air mixture is forced through the intake manifold and into the cylinders. When motorcycle carburetors get dirty or have a buildup of deposits, the performance level of the engine is affected. Rebuild a motorcycle carb on a workbench.

Turn off the fuel supply petcock at the underside of the gas tank. Remove the clamp that secures the fuel line to the carburetor. The camp may be held on with a screw fitting or small bolt. Remove the clamp and save it. Pull the fuel line off the carburetor.

Rotate the throttle cable adjuster at the handlebars counterclockwise with an open-end wrench to slacken the cable. Remove the clip that holds the throttle cable linkage to the carburetor and move the end of the cable out of the way.

Remove the nuts that hold the carburetor to the intake manifold with a socket and ratchet. Pull the carburetor off and place it on a workbench.

Remove the air cleaner from the carburetor. Depending on the carburetor, there may be a small bolt in the center of the air cleaner cap that is easily removed with an open-end wrench. If not, unscrew the air cleaner from the carburetor. Discard the filter cartridge.

Remove the small bolts that hold the fuel bowl to the bottom of the carburetor. Save the bolts. Remove the bowl and empty any residual gasoline into a container. Lift the float out of the bowl and set it aside. Remove the gasket from the rim of the bowl and discard it.

Turn the carburetor over and identify the brass main jet and brass idle jet. Remove the jets with a screwdriver and discard them. Unscrew the idle screw from the outside of the carburetor body. Remove the screw and tension spring and set them aside.

Spray the entire carburetor body and open ports with carburetor cleaner. Wipe away the cleaner with a rag. Spray the inside of the float bowl with cleaner. Wipe the inside of the bowl with a rag to remove any lacquer deposits. Spray everything one more time and wipe the cleaner away with a rag.

Open the carburetor rebuild package and organize the contents on the worktable. The kit should include two brass jets, a bowl gasket and the air cleaner cartridge. Refer to the instructions if additional components are included in the particular kit for your motorcycle.

Screw the main jet and idle jet into the ports on the underside of the carburetor body. The jets are different sizes and will only thread into the correct port. Tighten the jets with a screwdriver.

Replace the float into the fuel bowl. Put the provided bowl gasket on the rim of the bowl and reattach the bowl to the bottom of the carburetor body, using the saved bolts.

Put the tension spring on the shaft of the idle screw and thread the screw back into the side of the carburetor. Tighten the idle screw clockwise until it seats against the carburetor. Turn it counterclockwise one and a half turns as the preliminary idle setting.

Put the new filter cartridge in the air cleaner and reattach the air cleaner to the carburetor. Reattach the carburetor to the intake manifold on the engine. Reconnect the fuel line to the carburetor and secure it with the saved clamp.

Reattach the throttle linkage to the carburetor. Adjust the throttle cable at the handlebars to eliminate any play in the throttle cable.

Items you will need
  • Screwdriver
  • Sockets and ratchet
  • Spray carburetor cleaner
  • Carburetor rebuild kit

Tips

  • Refer to the rebuild kit by year and model of the motorcycle.
  • Carburetors vary in design and components. Refer to a repair manual for additional information and instructions.

About the Author

William Machin began work in construction at the age of 15, while still in high school. In 35 years, he's gained expertise in all phases of residential construction, retrofit and remodeling. His hobbies include horses, motorcycles, road racing and sport fishing. He studied architecture at Taft Junior College.

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