47mm GY6 50cc (139QMB) Piston Kit

47mm Piston Assembly for GY6 50cc Engines

This 47mm piston assembly is built for 50cc QMB139 4-stroke engines. Everything needed for a full replacement is included: the piston, rings, wrist pin, and circlips. It belongs to the group of GY6 50cc scooter parts that owners commonly replace during engine servicing or when upgrading performance. Installed correctly, it helps the engine run properly and last.

Part Dimensions

The piston has a 47mm outer diameter and an overall height of 34.4mm. The compression height is 17.25mm, the wrist pin diameter is 13mm, and the wrist pin length is 36.8mm. Matching these measurements is key to a correct fit and good engine performance.

Fitting Notes

Swapping the piston in a GY6 50cc engine is manageable for anyone comfortable with scooter repair. Check that every component is compatible and have the right tools ready before starting. Signs that a new piston may be due include lower compression and unfamiliar noises from the engine.

Specifications

• Size: 47mm outer diameter
• Total Height: 34.4mm
• Compression Height: 17.25mm
• Wrist Pin Diameter: 13mm
• Wrist Pin Length: 36.8mm
• Includes: Piston, Pin, Rings, Circlips
• Fits: GY6 50cc QMB139 4-stroke engines with a 47mm cylinder

Compatibility

Fits:

• GY6 50cc QMB139 4-stroke engines (47mm cylinder and head kit)

How to choose: Select a piston that matches a 47mm bore, 13mm wrist pin, and 17.25mm compression height. The cylinder needs to be the 47mm 50cc QMB139 type.

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