The 80cc (60 some cc) kit I bought is alot more fun than my first attemt at motorizing a bike. the first one had a engine from a 2 stroke snow thrower, it was fast at 35-38MPH but I had to remove the crank on the left side to install a pulley, so you couldn't peddle, just foot pegs.
lots of good info here, hope I can help with issues too that others may have.
see you guys/gals around
Stowah