NOTE!!!THIS CRANK HAS THE "SHORT" TYPE ROD SO PRE 1981 PISTONS AND HEADS MUST BE USED WITH THIS.. IE OUR OLD 70 HEAD OR ULTRA HEAD AND MATCHING PISTON KITS.. THIS CRANK WORKS WITH ALL XR50'S Z50'S XR70'S AND CT70'S THAT HAVE CDI IGNITION FROM THE FACTORY. "NOTE" YOU MUST HAVE A PISTON WITH TRIMMED SKIRT OR YOU MUST TRIM THE PISTON SKIRT SO IT WILL CLEAR THE CRANK WEIGHTS WHEN IT IS IN THE DOWN POSITION. I WILL MARK ALL OF OUR NEW PISTONS WITH **52*OK** SO YOU KNOW THEY WILL CLEAR THE 52MM STROKER CRANK. ALSO YOU MUST USE THE STOCK FLYWHEEL/STATOR AND CLUTCH OR DAMAGE WILL OCCUR!!!!! ALLWAYS ROTATE BY HAND BEFORE RUNNING TO MAKE SURE EVERYTHING WILL CLEAR!!! THEN HANG ON Racing crank 52 stroke for 12 volt engine complete with bearings and sprocket. TRX70'S ASK 200001