There are 2 Cylinder Head versions being factory installed in GY6 scooter engines. They differ only in the valve length. The old version ships in alm..
39 mm outer diameter piston for 50cc GY6 139QMB engines. This is the stock size 39 mm piston for Chinese built 50cc GY6 139QMB engine. This piston in..
There are 2 Cylinder Head versions being factory installed in GY6 scooter engines. They differ only in the valve length. The old version ships in alm..