[fastbmw]

I decided to swap my old 88cc top end onto my stock zb50 to test it out. The knocking sound is coming from the top end, so either I have a bum piston or wrist pin. I checked out the head and it looks great, no wear whatsoever. I guess I saved myself a few bucks.

 

[racerx351]

I would say a bad wrist pin!!!