Our Race Head has been updated for even more performance! It now has 25/22mm valves with better porting/flow. We also kept the combustion chamber the same size and changed the angle of the valves slightly. This will really wake up your stock engine and is comparable in power to the much larger Chinese 124cc engines!!! Includes the following: - Lightweight aluminum cylinder with steel sleeve - Cast in mounts on cylinder for aftermarket skid plates - Oversized cooling fins on cylinder for efficient heat dissipation - 52mm high compression piston with rings - pin - & clips - Head gasket kit - High performance race camshaft and Honda cam sprocket - Race Head – Larger valves (now 25/22mm) and better flow for increased performance. Also has bigger cooling fins. Includes all necessary parts and comes assembled!- The exhaust valve has been upgraded to stainless steel (21-4N material). - 20mm Performance carb assembly. Includes: 20mm carb - intake - heatstop - gaskets - mounting hardware/wrench - long adjustable throttle cable - and a air filter.- main jet kit is now included too! We recommend purchasing a high volume oil pump kit (available in this section). Installation Note: It will save a lot of time and effort if the oil pump is installed while installing the bore kit (requires cylinder removal).