i added a yoshi slip on with the spark arrestor removed and rejetted the carb to 170. the bomb runs good but some times at about 4000 rpms it stalls. seams not to do it in first gear, just all the others. anyone got any idea where to start?

 

Hi there. It sounds like you may be running out of gas. I know this may be difficult to do, but ride it and when it does it shut the gas off as fast as you can "at the pitcock" while letting off the throttle and pulling in the clutch. When you stop loosen your drain screw and see how much fuel comes out. If it seems like very little come out than I would say it is a fuel problem. If thats not the case then I am not sure. Hope this helps you out. RUSS

 

does it stumble and bog, or just shut off quickly? Did you adjust the needle at all? You might try raising the needle (lowering the clip) once notch, and seeing if that changes anything.