Thanks for your reply and I am really appriciate this website.I have one more asking again. When I run slow to a bad road/way or just like a hump, my RPM arise, if arise my RPM, it will ran fast for 5 seconds and back to normal. But when I run very fast, my RPM is very good. My mechanic replaced new cable accelarator and overhauled my carborator to spray in 2 bottles of carborator sprayer. But still the same problem with my RPM.