How big are the tires and how many teeth on the rear sprocket? And yes, you will need to tell us the pitch of the rear sprocket. 3/8" (#35) or 1/2" (#41, #40, or #420)? And the engine shaft size.
---------- Post added at 12:53 AM ---------- Previous post was at 12:34 AM ----------
Guessing 60 teeth and 18" Tires and 1/2" Pitch with a 1" crankshaft
So a 1" bore, 10T, #41/#40/#420 clutch (if my assumptions are correct).
Something like this for flat riding
http://www.gopowersports.com/10t-1-bore-centrifugal-clutch/
Or maybe this 1" 30 series TC? Is that a real thing?
Will probably be an issue to mount the TC tho. Maybe Lifting the engine, removing the gas tank,.... Ask GaryQuick how difficult it was for him. LOL
http://www.ebay.com/itm/GO-KART-TOR...MS-/252796200710?_trksid=p2385738.m2548.l4275
The Torque Coverter is a better option than a Cent.Clutch. Big Tires and CC's don't mix very well.