I completely grafted a DS-50 into my wife's bike. Update!!! A 52.5 mm Namura Kawasaki XK-100 piston in a sleeved 47 mm Metrakit cylinder was used with a Derbi TOP flat reed crankshaft - competition crank re-balanced by Crank Works in Arizona. I must say they did a super job. 6 holes on the inside surfaces slugged with tungsten and ground flat. No "stuffing" necessary! Still has a bit of vibration at the 3 and 9 o'clock position which is unavoidable. Hauls A**? 2.3 Gallon modified gas tank also.