Thanks for answering, guys... what I meant by a shorter plug is that he changed my plug from an NGK B7HS to a B6HS, I believe it is.. it's a colder plug, the metal arm coming off the bottom of the plug is shorter....I have to really peddle my bike like hell now to get it running from a cold start..but once it warms up for even a minute it can restart very easily.He did that because I think he was worried about the new larger piston hitting the bottom of the plug, so he opted for the B6HS with the shorter metal arm..
I had this mod done to my Avanti moped....so far gets about 5 mph increase in speed...If it loosens up and lets me run at full throttle without overheating it will be a great moped to keep up with traffic ..I think everything is tight yet because she gets real hot when I go up-hills. I've driven about 90 miles and it may be starting to loosen up a bit...But it's frustrating having to run at half-throttle, ain't it ?? !! Still, at half throttle she's doing about 25mph so it's not like I'm dragging too bad...my old Puch only does about 24mph full throttle :)
I'm still using the old carb,I won't opt for a larger carb until this motor proves to me that a break-in period will let run at normal temperatures.
I was just hoping that I might hear from others who have had a similar piston kit put in and that maybe they had to run theirs at half-throttle for a few hundred miles also before their motor loosened up and ran at normal temp ?