Newish rider with bikes but eager mechanic..Probably something that's been posted a million times.. Anyways just picked up an '05 yz450 the first 3 gears engage flawlessly however as soon as it's dropped into forth and I hit the throttle it seems as if it's hesitating. The closest thing I could compare it to is a governor (but then again why would it be hitting almost as soon as it's placed into gear) limiting me from my top speed. Granted I know whilst riding most of the times I'm never going to be going full bore anyways. I'd still like to know if this an issue I should be concern about or not? Previous owner stated 10 hours on a top end rebuild to which to what I've been told is a long time. Any help would be great thanks in advanced. Feel free to ask any further questions for clarification.