Wikipedia mentioned that some people convert QT50s to use a Yamaha MJ50 Towny two-speed crankcase.
"Popular modifications include: Yamaha YT60 cylinder, piston and rings. Yamaha MJ50 Towny two-speed crankcase and right-side swingarm. Yamaha PW50 rear gears. Mikuni VM15 and VM18 carburetors. Jemco exhaust, etc."
Does anyone have more info on this swap? How hard it is? the parts required? Cost? Having a hi and low gear woudl wake the QT50 up a lot I think.