NCY 139QMB Performance Cylinder Head 81cc 50mm

The NCY 81cc Aluminum Performance Cylinder Head is a direct upgrade for 50cc 139QMB-based engines. Pair it with NCY's 81cc Cylinder Kit to push past stock displacement and gain the power needed for city traffic and hills. Made in Taiwan. ISO 9001 certified. NCY has been the aftermarket performance leader for popular scooter platforms since 1997. Key Features 81cc alloy performance cylinder head for 139QMB / GY6 50cc engines 50mm stud spacing — direct fit for QMB/QMA engine families 64mm valve stem height — requires 64mm rocker arm assembly (not included) 6mm intake and exhaust threads ISO 9001 certified manufacturing Specifications Stud Spacing: 50mm Head Height: 60mm Intake Port: 24mm Exhaust Port: 22mm Intake Valve: 21.5 x 64mm Exhaust Valve: 19 x 64mm Valve Stem Diameter: 5mm Valve Stem Length: 64mm Intake Threads: 6mm Exhaust Threads: 6mm Head Height w/ Intake Valves: 66.1–67.3mm Note: Most stock 139QMB heads use 69mm valves and a 69mm rocker arm. This head uses 64mm valves and requires a 64mm rocker arm. Verify your stock valve stem height before ordering. Compatibility Fits 139QMB-based 50cc / 80cc engines with the following engine codes: Engine Codes 139QMA, 139QMB, 1P39QMB, 1P39QMA-2, YN139QMB, JJ1P39QMB, 139FMA-2, BD1P39QMB, BN139QMB, 147QMD, Other QMA/QMB models If your engine code includes "QM" or "FM" and your valve height and rocker arm are 64mm, this head is compatible. Visit our Shop by Diagrams page to confirm fitment. Performance upgrades are considered racing parts and are not covered under warranty. This product is intended for off-road use only. Not legal for use in California on pollution-controlled vehicles. Check local laws before installing. California Prop 65 Warning: www.p65warnings.ca.gov