How do you fine tune a Honda Keihin carburetor?

To fine tune a Honda Keihin carburetor, adjust the idle screw, air/gasoline adjustment screw and other parts as necessary. A professional mechanic can help if the car owner is unable to do the work himself, says Keihin Carbs.

To fine-tune a Honda Keihin carburetor:

1. Adjust the idle screw

Adjust the idle screw up to the desired minimum RPM depending on the type of ride. Make sure the engine is up to operating temperature.

2. Adjust the air/gasoline screw

Locate the air/gasoline screw, which may be upstream or downstream of the throttle valve. If upstream, turn counter-clockwise to lean the mixture off idle. If downstream, opening the screw will result in a richer fuel mixture.

3. Adjust the 1/8 to 1/4 throttle slow jet and throttle valve cutaway

If the idle screw has been adjusted but the engine still does not have a good response when the throttle is wide open, try replacing the slow jet with a larger one and adjusting the air/gasoline screw. If this doesn't work, try replacing the slide with a different number cutaway. A smaller cutaway will let less air in and create a richer fuel mix.

4. Adjust the 1/4 to 3/4 jet needle

Replace the needle with a smaller model for a richer mixture. Adjust the clip position to change where the needle begins to taper.