YZ426 carburetor question

[yz450scott]

how do I adjust the screw with the spring above the accelerator pump rod just below the throttle cable connections at the carb. I am not sure what is does and my manual if very vague..?

[FrankV]

Do you mean the one which is directed to the other side of the carb and has a black knob? That's the idle adjust (it raises/lowers the throttle valve).

[grayracer513]

That screw is for the adjustment of accelerator pump timing. The '01 manual doesn't cover it at all, really. Download an '03 manual here:

http://www.yamaha-motor-europe.com/community/service/manuals.jsp

Look at the procedure on page 4-19 and use that as a guide. Then review this thread:

http://motoman393.thumpertalk.com/tech/carb.html