THIS WORKS TO CONVERT A 50CC TO A 85CC DISPLACEMENT ON THE FOLLOWING HONDA MODELS. ALL XR50'S ALL CRF50'S Z50R 1982 THRU 1999 REPLACEMENT KIT COMPONETS ARE LISTED BELOW!!!!!!!!!! XR50_CRF50 Z50R_1982_TO_99 85CC_CYLINDER_KIT (MARKED_49CC) (600024) 1-9/2-10/1-46$124.99 51MM_BORE (63MM/SHORT) STEEL_CYLINDER (MARKED_49CC) (100009) 51MM_BORE (63MM/SHORT) STEEL_CYLINDER (MARKED_49CC) (100009) 100009$62.95 51MM_BORE (63MM/SHORT) ALLOY_CYLINDER (100011)FITS MOST ALL HONDA 50'S AND 70'S 68 THRU 05 100011$87.99 TOP END GASKETS ** PICK BORE SIZE ** 39 47 51 52 MM THIS KIT HAS EXTRA PARTS YOU WON'T USE,, THIS WAY IT WILL WORK FOR DIFFERENT MODELS. FYI STOCK 50'S = 39MM ALL Z50A Z50R XR50 CRF50 = 39MM ALL XR70 CRF70 = 47MM CT70 ALL = 47MM ATC70 ALL = 47MM C70 PASSPORTS ALL = 47MM C70M'S ALL = 47MM 85CC KITS = 51MM 88CC KITS = 52MM TRX90 = 47MM TRX90 103CC = 51 TRX90 106CC = 52 THIS WILL WORK FOR ALL YEARS OF 50'S 70'S AND TRX90'S PICK_BORE_SIZE SEE DROP BOX BY ORDER BUTTON 39MM_ 200008 47MM_ 200009 51MM_ 200010 52MM_ 200011 TOP END GASKETS ** PICK BORE SIZE ** 39 47 51 52 MM 200008 / 200009 / 200010 / 200011$13.99PICK_BORE_SIZE: 39MM_20000847MM_20000951MM_20001052MM_200011 51MM_PISTON_KIT (NEW_50_DOME) (LONG_ROD) (SHORT_CYLINDER) (100046)FITS ALL XR50 CRF50 AND 1982 AND NEWER Z50R'S WHEN YOU HAVE A STOCK HEAD AND CRANK 100046$51.95