If you have experienced gear selection issues resulting from not using the clutch properly or stamping through the gears this is the cheapest solution available, no time-consuming gearbox re-builds. Simply remove head / barrel / piston / clutch / oil spinner / flywheel / stator and move to the new engine. Will fit all Stomp, WPB & Demon X pit bikes with Lifan 120 engines. Please note that some older Stomps were fitted with GN engines. All Lifans have 14mm gudgen pin.