80cc puch hybrid

• Author: clay (---.tc.ph.cox.net)
• Verified User: clayy
• Date Posted: 10-28-09 00:14

i know this isn’t technically a moped, but it has moped parts. maybe you all won’t boo me off of here.
anyways i started with a 66cc chinese bike motor that had reached the limits of the stock cylinder. which has a bore of 47 and a stroke of 40. so i found out the headbolt spacing was very close to a puch, BINGO! reeds and nikasil on the way. now my motor is smaller because the puch has a stroke of 43. the only thing i could do was stroke it, 10mm…..



i built the removeable balance pads out of aluminum to replace the cast iron ones that came stock. balanced the crank with brass slugs for a target rpm of 9000rpm (i hope 53% was right for 9k)




transfers and 7mm cylinder spacer




my port timing ended up being 176 on the exh and 132 or 136 on the transfers. since i dont have a centrifugal clutch my exh timing needs to be a little more conservative



lead in pipe is 10.75” with a 2deg taper. then 10” of 6deg taper. 3.25” of 12deg taper next. chamber is just under 3” dia and 5 inch long. the baffle cone will be 16 deg maybe (feedback on this point would be greatly appreciated)





carb is off a 110 4stroke pitbike. i believe you would call it a 22mm mikuni, but the venturi is oval shaped so i have no idea.



have i done anything extremely wrong?