GY6 engine O-ring Oil pump mounting screw o-ring on crankcase compatible scooters equipped with GY6 engine 50 cm3 4 time. Dimensions: Outer diameter: 12 mm Inner diameter: 9 mm Thickness: mm 1,5 GY6 engine 139QMB 50 cm3 (49,9cc) 4 engine mounted on AJS, Adly, scooters Aeon, Baotian, Beeline, Branson, Daelim,