sweet build simple and effective. I made something very similar with a brake lever pulling it up or down to act as a clutch, Brake line eventually gave out and i moved to a 78mm clutch mount to the motor and a bearing supporting the other end and then at he very back there was a long threaded screw with a threaded nob for hand tightening the tension of the knurled finished spindle to the rear tire. it did the trick, I got the bad boy with speeds of 45mph pulling out over 5 hp on that engine, it was scary. Tires didn't last very long nether