I've got a '84 XL600R(dual carb) recently rebuilt(new .25mm oversize piston/ring, valve job, carbs rebuild) that is now running fine except for two things : 1. When I start it(most of the time at first kick), I have to wait at least 15 minutes before removing the choke(at 75 degree F); otherwise, it will automatically stall(lean mixture?). The only way to keep it alive with the choke off before the end of the "warmup", is to always give a little bit of throttle until it's fully warmed up. 2. If I remove the choke before the end of the "15 minutes warm-up" and it stall, it will be a real pain in the ass to restart. Sometimes, it's impossible to restart and I have to wait until it's cold to restart it. If it stall after the choke warm-up, it always start at first kick like when it's cold. I suspect that thoses two problems are linked together... I don't know if they are the stock jets, but my jets are the following actually : Primary carb pilot jet : # 58 Primary carb main jet : # 122 Secondary carb main jet : # 120 If I momently increase the idle speed during the warmup with the idle adjusting screw, it'll not stall, but as the engine is warming up, the idle speed will increase more and more, forcing me to compensate by unscrewing the idle screw; which is, as you guess, really annoying. I tried to put a # 65 pilot jet and # 125 main jet on the primary carb, but it made no difference at all. So now, my question is : What could it be??? THANKS!!!