I have a 99 XR650L. I had it bored out and a 101mm JE piston put in. I also had a white brothers all around cam slotted and degreed in. I had a full white brothers e-series set up put on header and all. I also had a little mild porting done. I bought a Keihin FCR 41mm carb and my mechanic installed it for me. I don't think he set it up correctly though. From what I understand the accelerator pump should give quite a kick when I slam the throttle. The power gain has not been to noticible and am currios if there is a adjustment that was neglected on the accelerator pump or on another part of the carb. The menhanic said that the carb was jetted a little rich to be on the safe side. I am not to familiar with this carb and would be very thankful for any help I can get here.