Hi, I have a 66cc bike. Motor is ported and has a nice homemade exhaust. So pretty much the bottom end power is horrible right now, I mean HORRIBLE. But once you get to the top end its much better. It idles very high, and turning the screw doesn't really do anything. It also revs very high at random times. I thought it was a carb problem but It is not b/c I tried like 4 carbs and it did the same thing. I tried new spark plug, new plug boot, new CDI, almost everything. Could it be a blown crank seal? The symptoms are very similar, exept I took all the covers off and no oil is leaking. Also, I don't know if this matters, but my gear case gasket is blown ( like only 1/2 of it is on)