Hi Micke here and im all fresh here and not so good to write in english so bare with me:) Ok i have a yz400f 1999 that is running really bad. I have searched the forums and found a Lot of threads about almost the same issue that i Have. The top end is rebuilt so the valve clearence is good. My bike starts but it wont rev up properly. The engine reaches a high temp really fast. It pops when i reduce the throttle. Lack of power. This happens almost every time i start it after a couple of days. But sometimes i leave it for a couple of hours and try to start it again it runs good. I have cleaned the carburator and replaced some worn parts, o-rings, needle valve, acc pump rubber. Anyone got any ideas?