THIS MUST BE !! USED WITH THE INCLUDED PISTON KIT USED WITH A CDI FLYWHEEL/STATOR USED WITH THE NEW TYPE THIN OIL PUMP DRIVE SHAFT AS SEEN BELOW USED WITH A STANDARD 63MM TALL CYLINDER IN 52MM OR 54MM BORE (54MM REQUIRES BIG BORE CASES) AND !! USED WITH A BIG DOME RACE OR OLD TYPE 70CC 22MM AND 25MM VALVE SIZE HEAD 86Y/(1-42"OR"54/GBO)PICK_PISTON_SIZE: 52MM_110CC_10004254.00MM_120CC_(54/GBO)(S1109)