Cylinder Head WM – for 80/90ccm GY6 4T – 139QMA / 139QMB Engines

Description

The WM cylinder head is designed for use with 80cc or 90cc big bore kits on GY6 50cc 4-stroke engines (engine codes 139QMA and 139QMB). It’s a perfect match for upgraded cylinders, offering improved valve flow, combustion, and overall engine breathing, especially in tuning setups.

Ideal for replacing a damaged stock head or for completing a full big bore conversion, this head is pre-assembled with valves, springs, and retainers, ready to bolt on.

Compatible with:
– GY6 50cc base engines upgraded to 80cc or 90cc
– 139QMA / 139QMB engine types (commonly found in Kymco, Baotian, Keeway, Sym, etc.)
– Works with big bore kits (47 mm / 50 mm pistons)
– Air-cooled scooters, ATVs, and pit bikes using horizontal GY6 4T engine

Specifications:
– Designed for: 47–50 mm bore (80/90cc)
– Valves: Pre-installed (intake & exhaust)
– Valve size: Compatible with stock or slightly enlarged valves
– Material: Cast aluminum
– Cooling: Air-cooled