Blown crank seal?

GoldenMotor.com

fischerking45

New Member
Jan 30, 2012
7
0
0
California
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)
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
The gear case being the right side engine cover? If so, no. That gasket does nothing to hold in crankcase pressure, positive or negative.

If you see no evidence of oil or fuel residue in tne magneto side or from behind the small gear in the right side, then I'd go back to your carburetor/intake manifold and re-check things there. Just because the carb is tight on the manifold doesn't mean it can't leak air. We suggest that a gasoline resistant sealer such as SealAll be used to assure that you have no air being drwn in behind the carburetor inlet.

Your symtoms are consistant with an air leak so keep looking.
Tom