98% OF YOU WILL HAVE TO FIND A MACHINE SHOP TO INSTALL THIS KIT !! IF YOUR OLD PARTS ARE GOOD YET (IE ROD/BALL BEARINGS/CHAIN SPROCKET) ALL YOU NEED TO BUY IS THE CORE KIT AND YOU WILL HAVE ALL THE PARTS TO MAKE YOUR 89CC INTO A 120CC ENGINE YOUR CYLINDER WILL NEED TO BE BORED TO MATCH THIS PISTON, WITH .001" TO .002" CLEARANCE YOUR CRANK WILL NEED TO BE PRESSED APART THEN BACK TOGETHER AND TRUED UP WITH A .004" LOWER ROD SIDE CLEARANCE