Well, I discovered motors for bikes about a month ago and since then have mounted a skyhawk 5 on my 9 yr old girl's Schwinn chopper. Man, what a ride! I love it so much that I went out on criagslist and bought a couple more choppers and intend to make a couple more motorized bikes.
I went through my old motors and found a ryobi weedeater motor and took out the little pressure clutch and put in a chainsaw clutch. I had to tap the chainsaw clutch but it seems to work on the mock up so far. I took the rear sprocket off of one of our old children's bikes and it fit like a glove over the ryobi clutch with little modification. Now I have a motor with a chainsaw clutch and sprocket. I also took the front sprocket and made it into the lower drive sprocket.
My wife hates this stuff because it is eating up all of my spare time. I may have to start making parts on my cnc machine soon.
Love this site.