Upgrade your GY6-50 QMB139 scooter engine's performance with this comprehensive 80cc Big Bore cylinder kit. The kit features a precision-engineered 47mm cylinder and piston assembly designed to increase your engine's displacement and power output. This complete top-end rebuild kit includes all necessary components for installation, including the cylinder, piston, rings, and gaskets. The aluminum cylinder construction offers excellent heat dissipation properties, while the matched piston and ring set ensures optimal compression and reliability. Perfect for riders looking to enhance their scooter's acceleration and top speed capabilities, this kit represents a significant performance upgrade over the stock configuration. Installation should be performed by experienced mechanics familiar with GY6 engine work to ensure proper clearances and assembly. This kit is specifically designed to fit QMB139 engines commonly found in 50cc scooters, providing a direct bolt-on upgrade path for increased displacement.