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Rolling Wrench

GY6 50cc Final Drive High Speed Gear Up Kit (Includes Pressed Gears, Gasket & Oil) - QMB139

GY6 50cc Final Drive High Speed Gear Up Kit (Includes Pressed Gears, Gasket & Oil) - QMB139

$88.00 USD
$88.00 USD
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Shipping calculated at checkout.

Get more top speed out of your 50cc QMB139 scooter. This gear-up kit swaps the stock gearbox gears for a taller final drive, so the engine turns fewer RPM at any given road speed. Everything you need for the swap is in the box. Pick your gears based on your engine displacement.

🔍 Does this fit your bike?

  • GY6 50cc scooters with the QMB139 (139QMB) engine.
  • Not for 150cc+ GY6 engines (QMI152 / QMJ157). Those need our ➡️ 150cc+ gear-up kit. ⬅️
  • Real-world top speed depends on your engine, CVT setup, rider weight and conditions, and the gains are smaller if the engine can't pull the gearing. Not sure what engine you have? Check the engine code stamped on the case.

⚠️ Before you order

  • Expect some low-end loss. Taller gearing trades acceleration for top speed, and a 50cc engine has little torque to spare.
  • Best on built engines. A stock motor will see less benefit.
  • Works best with a tuned CVT. Variator weights or sliders help the engine pull the taller gearing.
  • Install is easiest while you already have the CVT or gearbox cover off.
  • No returns on performance parts. Double-check your engine and option before ordering.

✓ What's in the box

  • Gear set (countershaft gear and final drive gear)
  • Gearbox gasket
  • Gear oil
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