So a few months ago I had nothing to do in my high school shop class and decided to do something about that. I took an old Quad of mine and a blown up engine from a 1989 Cr80R. I took the engine apart, cleaned and rebuilt it along with boring the cylinder out to 105cc, porting and polishing the intake and exhaust, grinding the head down to bump the compression ratio up a bit and throwing some race gas at it. Took out the old Chinese 110cc engine from the quad and reinforced the frame as much as I could adding engine mounts and a few other things. In the end everything seemed to fit together perfectly and ran great after breaking the engine in, tuning and messing with gearing ratios. It's crazy fun to ride around the streets and not really practical off-road because of the 1 1/2" ground clearance but overall a good fun project.

 

Welcome to the forums.
Glad you had fun.

 

Now this is a shop project I would have loved to have!