Glixal ATMT1-012-2 GY6 23mm Big Valve Cylinder Head Assy 50cc to 100cc 50mm for 139QMB 139QMA Chinese Scooter Moped ATV Go Kart Quad Buggy (Non EGR Type) Valve Length-64mm Intake Valve Diameter- 23mm (Stock is 18.5mm) Exhaust Valve Diameter- 20mm (Stock is 16mm) Combustion Chamber Diameter-50mm This a Non EGR Head, Does Not Have the EGR Port