These are some great stories, and yeah Stephen, i can see how a 50cc one would be WAY too fast for safety.
Just got a Zenoah G320RC engine coming in the mail (Largest standard RC series engine at 32ccs) The bike came with the "Sikk expansion" pipe with centerbleed lol... i got a silencer for it.
The engine i got with it was a chung yang which is a Zenoah (Japan) copy. lots of these gopeds come stock with smaller zenoah rc engines from 22cc to 32cc. The chung yang has QUITE A BIT TOO MUCH end play on the crank to wanna use with a bike with new tires, a new clutch etc
I plan on avoiding on road use at all costs on this little folding scooter, if i ever took it on the road I would attach a moped plate. With all the noise I make, I always follow the rules and the cops haven't bothered me at all yet