80cc Big Bore Kits 139qmb Gy6 50cc Engine(64mm Valve) 139qmb 139qma Scooter Moped Parts #70001 This kit fits with most Chinese Scooters/Mopeds with 50cc, 60cc, 4-Stroke GY6/139QMB engines!!! This bore kit can rebuild your 50cc 60cc 70cc 90cc bike to 100cc. This will increase your powerband anywhere from 50-75% so be ready to go faster!!! 70001 is for long valve 64mm version,( if you need 69mm version, please refer to the item NO.: 88806