GY6 50cc (139QMB) Transmission Bearing & Seal Kit

Transmission Bearing and Seal Kit for QMB139 Engines

This full transmission bearing and seal set is made for 50cc QMB139 engines and covers everything needed for a complete gearbox overhaul. It supports steady, reliable power transfer, so it's a sensible pick for keeping your engine running well. As one of the GY6 50cc scooter parts options, it bundles every required piece into a single box, so you won't have to hunt down each item separately. Whether you do your own repairs or work on scooters professionally, this kit has what you need to finish a transmission rebuild.

Components Included

The set contains the bearings, seals, and gasket used in a standard transmission rebuild. Inside you'll find one each of the 6303, 6203, and 6004 RS bearings, plus three 6201 bearings. The kit also includes two oil seals (17×30×6 and 27×42×7) and a gearbox gasket so the assembly is complete. Together these parts let you restore your gearbox in an efficient, straightforward way.

When to Replace Transmission Components

Keeping transmission parts in good condition is important for dependable operation. Unusual noises or trouble getting power through the drive can point to worn components that need replacing. Using this kit lets you deal with those problems quickly and keep your engine performing consistently.

Specifications

• Fits: Compatible 49cc/50cc 139QMB / QMB139 engines (GY6-style transmission)

Fitment

Fits:

• 49cc/50cc 139QMB / QMB139 engine
• Other models using the matching QMB139-style transmission

How to choose: Confirm the engine is a 49cc/50cc 139QMB / QMB139, then check the bearing numbers (6303, 6203, 6004 RS, 6201) and seal sizes (17 × 30 × 6mm, 27 × 42 × 7mm) against your old parts.

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