i have a 90' 650 sx when i start it i run it for a min. to just to get it up in temp a little then go out and it runs perfect for about 5 to 10 mins. depending on how hard im riding. Seems like once its warmed up it bogs so i have to feather the throttle still idles and will rev out but i have to feather it. the motor doesnt sizzle so i dont think im overheating if anyone has any insite it would be greatly appreciated