Theoretical way to make a cheap 79cc friction drive.
So I haven't actually tried this, but the idea popped into my head and it's too simple to not throw out there. You could take a 79cc predator, or any similar or larger 4 stroke, and a centrifugal clutch like a max torque, and use the outside of the centrifugal clutch as the roller to drive the wheel. You might have to grind some grooves in the outside of the clutch to help it grip the wheel. I would think that since the clutch is like 3 or 4 inches in diameter, the gear ratio would be pretty much perfect for a 79cc if you used something larger than a 26" tire. 26" would probably be pushing it though. You could probably build this friction drive easily for under $200 (not including a bike). Thoughts?