I am a human f-3 manual.my bike would not run . turns out ihad avalve leak & no money. i dissasembled it lapped the valves I rebuilt my cyl. head no new gaskets i got another 1700 mi out of it then i bought a used head on ebay cams & all 4 $65.00 then i found a set JE forged pistons 13.5-1 comp 637cc ebay $109.00 The best bill I ever spent I think he was an angel turns out he builds motors for micro sprint cars $ his are always winning in 2004 he uses cbr f-2 f-3 motors to make a long story longer I have the blueprints.4 only $19.95 you can have them 2 because I dont have the money for the machine work.E mail me & explain the problem w/your f-3 i gaurantee i can tell you how too fix it. if i cant i will give you the blue prints free.email. ugd420@yahoo.com