needing a lottba help, ive got a 98 big bear 350 motor was rebuilt 6 months ago, by someone i dont know it will not rev past 14 throttle, will not pull itself, valves are good, carb is good, timing is good, starts quick and easy, 120 psi with my compression tester, new plug, fresh battery, only thing that gets my thinking is that there is a lot of pressure coming in and out with stroke out of the crankcase breather on top of the head. any insight would be greatly appreciated as i am at my witts end