THIS CRANK WORKS WITH ALL CT70H'S (HAND CLUTCH), XL70'S SL70'S CL70'S THE RIGHT SIDE OF THIS CRANK IS LONGER THAN THE OLD Z50'S (68 TO 81) AND CT70'S (69 TO 81) THAT IS WHY IT DON'T WORK WITH THOSE MODELS "NOTE" THREE THINGS!! ONE--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. OUR 85CC AND 88CC CYLINDER KITS HAVE THE TRIMMED PISTON SKIRTS ALLREADY !! TWO-- YOU MUST REMOVE 1MM TO 2MM OF METAL FROM THE CENTER 1.5"S OF THE OIL PUMP DRIVE SHAFT SO THE ROD WILL CLEAR ON THE DOWN STROKE, OR BETTER YET BUY OUR HIGH OUTPUT OIL PUMP KIT (270% OVER STOCK) AND YOU WILL GET A TRIMMED PUMP SHAFT INCLUDED FREE. THIS OIL PUMP IS RECOMMENDED WHEN USING THE STROKER CRANK!!!! THREE-- ALSO YOU MUST USE THE STOCK FLYWHEEL/STATOR AND CLUTCH OR DAMAGE WILL OCCUR FROM BEING OUT OF BALANCE!!!!! ALLWAYS ROTATE BY HAND BEFORE RUNNING TO MAKE SURE EVERYTHING WILL CLEAR!!! THEN HANG ON... 200002