80cc Big Bore Kit Cylinder 69mm Head Piston Rings Chinese Scooter 50cc 60cc GY6 80cc Big Bore Kit with 69mm Valve Head Assembly Need Faster acceleration, and more top speed to keep up with the flow. Then our Big Bore Kits are the way to go. For scooters with 139QMB or 139QMI engines Scooter Before ordering check your head assembly for the correct valve length. See the 2nd and 3rd listing images. If you need a different BIG BORE KIT click link below 64mm Head 80cc Big Bore Kit w eBay Item# 291567626384 69mm Head 80cc Big Bore Kit w eBay Item# 271616884375 64mm Head 100cc Big Bore Kit w eBay Item# 281816759859 69mm Head 100cc Big Bore Kit w eBay Item# 271116277724 Specs Intake Valve Diameter: 18mm Exhaust Valve Diameter: 16mm Head Assembly with 69mm Valves 80cc Cylinder Diameter: 47mm Includes Head Assembly with 69mm Valves Cylinder Piston Ring Set Wrist Pin Cirq Clips Head and Base Gaskets