GY6 50cc (139QMB) Big Bore Kit with Head 4T (72cc, 64mm Valves)

72cc Big Bore Upgrade Kit for 50cc 4-Stroke Engines

This 72cc big bore kit is built to raise the output of 50cc 4-stroke engines, with the 139QMB models as the target. It offers a simple route to increasing your engine's displacement at a reasonable cost. Among GY6 50cc scooter parts, it suits riders who want more power without turning their scooter into a race build. Check your valve stem dimensions for compatibility before you buy.

What's in the Box

Everything needed for the engine upgrade is included. The package contains a head assembly with 64mm valves, an iron cylinder with a 47mm bore, and a piston fitted with rings. You will also get a wrist pin, circlips, exhaust and intake studs, and base and head gaskets to finish the job.

Fitting Guidance

Measure your scooter's current valves accurately before starting. This kit is made for engines using 64mm valves. Scooters with 69mm valves need a different kit. Correct fitting is what delivers the intended performance gains without complications. Follow standard procedures when swapping engine components so everything keeps working as it should.

Specifications

• Material: Iron Cylinder
• Size: 72cc
• Position: Engine Head
• Fits: CSC Go Max with 50cc 139QMB engine (64mm valves)

Compatibility

Fits:

• CSC Go Max (50cc 139QMB engine, 64mm valves)

How to select: Take the valve out of your head and measure the full stem length. This kit requires 64mm valves, not 69mm.

Placement: Part #13 on the cylinder crankshaft diagram for the CSC Go Max.

Alternate versions: For the 88cc 52mm kit for 139QMB/GY6 50 engines, see 88cc Big Bore Kit (52mm) - 50cc (139QMB) / GY6 50. For the 81cc 50mm iron kit for upgrading 139QMB 50cc engines to 81cc, see GY6 50cc (139QMB) Cylinder Kit 4T (81cc, Iron, 50mm).

Browse further: GY6 50cc Scooter Parts (139QMB) · GY6 Scooter Parts · Scooter Big Bore & Cylinder Kits · Scooter Cylinder Heads & Valves · Scooter Parts