air fuel mixture screw

[boricua]

sorry to annoy, but im hearing many people say different things about the the ari/fuel mixture screw. some say that it controls how the amount of air going through it, others say its fuel.....
i have a '00 ex with a keihin carb, what does my screw control, air or fuel?

[cals400ex]

the 400ex's have a fuel screw. some other carbs have an air screw though. i think many of the yamaha bikes with mikuni carbs come with the air screw. the fuel screw is a fine tune adjustment for the pilot jet. the more you turn it out, the richer the jetting becomes from approximately idle to 1/8 throttle or so.

[boricua]

thanks i'll keep that in mind

[300exOH]

I think it is actually called a pilot screw

cals400ex is right it is actually a fine adjustment for the pilot circuit

[cals400ex]

yes, you are right. when i actually use the correct terminology, people get confused. what everyone calls the pilot jet (stock 38) is actually the slow jet if i remember correctly. the pilot screw is what everyone refers to as the fuel screw.

[panteramatt]

Yes on most 4 strokes the screw is a fuel screw and controls the amount of fuel.On 2-strokes it measures air.

[PunkA$$]

An adjustment screw on the front side of the carb (engine side) will be a fuel screw, in leaner, out richer. An adjustment screw on the back side of the carb (air filter side) will be an air screw, in richer, out leaner.