Ultimate power for the Honda CRF50 and 12V Monkey bikes. 138cc 4 valve Superhead bore and stroke kits with auto decompression technology, forged aluminum roller rockers, two 21.5 intake valves, two 18.5 exhaust valves, Takegawa special hard coated and totally redesigned crankshaft, and four optional 4 valve camshafts. Unprecedented horsepower and throttle response from a base 50 engine case. The 138cc SCUT piston and cylinder require no case boring.