GY6 50cc (139QMB) Brake Sight Lens Replacement 18mm

Brake Master Cylinder Sight Window for GY6 50cc and 139QMB Scooters

This brake sight window is made for the brake master cylinder used on GY6 and 139QMB engines. It lets you check the brake fluid level while the system stays sealed. It is one of the GY6 50cc scooter parts that makes routine checks simple, so you don't have to swap out the whole master cylinder.

Drop-In Replacement for Stock Parts

This sight window works as an OEM-equivalent part and sits right into the factory brake master cylinders on QMB and GY6 engines. It is built to a tight fit, so restoring your brake system is straightforward.

Complete Kit for Installation

An O-ring gasket comes with the sight window to help create a secure, leak-free seal. This gasket plays an important role in keeping the brake fluid at the correct level and preventing leaks that could affect braking.

Specifications

• Size: 18mm Outer Diameter
• Includes: Sight lens and O-ring gasket
• Fits: GY6-based 50cc through 169cc scooters with QM or FM engine codes (139QMB, 157QMJ families)

Fitment

Fits:

• GY6 139QMB-based 50cc and 80cc engines (139QMA, 139QMB, 1P39QMB, 1P39QMA-2, YN139QMB, JJ1P39QMB, 139FMA-2, BD1P39QMB, BN139QMB, 147QMD, other QMA and QMB models)
• GY6 157QMJ-based 125cc, 150cc and 169cc engines (157QMJ, 161QMK, 152QMI, 1P61QMK, YN1P57QMJ, 1P52FMI, 154FMI, JJ157QMJ, 1P57QMJ, BN157QMJ, BN161QMK-A, other QMJ, QMK and QMI models)

How to choose: Check your engine code. If it contains QM or FM, the sight window will fit your stock brake master cylinder.

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