honestly it doesnt really sound to me like you need cubs. if your stock cylinders arent damaged id just stick with them. also, you really dont need the 4mm crank. if you go with a 4mm crank with stock cylinders youll have to have the cylinders ported to match the stroke of the crank. thats the best way to do it. personally, i say buy a new crank, pistons, bore your cylinders if necessary.. then if you have extra money and you want more performance you can buy bigger carbs, reeds and pipes. it will be like a whole new bike. how much money are you looking to spend? that will help determine what you need to do.