Hi Greg, this is a common thing in my shed be it 125 or 250. After wrecking my 250 gearbox at the nationals I put a mt gearbox in my cr but put the cr barrel, head, carby etc on it. I took this set up to the SA state titles and jagged a first. It did have a 125 ignition system tho with the small rotor/flywheel set up. Have a tinker and enjoy.