PRE-PRESSED & READY TO INSTALL — NO HYDRAULIC PRESS REQUIRED!

This is the biggest advantage of this listing.

Unlike standard NCY gear sets that require a 50-ton hydraulic press to swap the drive gear onto the countershaft, our gear set comes professionally pre-pressed and assembled, saving you time, money, and the hassle of finding specialized equipment.

Simply install the gear set using your original 42-tooth countershaft gear and get back on the road faster.

Increase Top Speed Without Sacrificing Rideability

Unlock the full potential of your GY6 performance build with the NCY 15T/38T Final Drive Gear Set. Precision manufactured in Taiwan, this transmission upgrade delivers approximately an 18% taller final drive ratio than the factory 13T/40T gearing, allowing your engine to cruise at lower RPM while increasing overall top-end speed.

Perfect for riders looking for a balanced transmission upgrade that improves highway cruising without making the scooter feel sluggish.

The final drive gears are the last reduction gears inside your GY6 transmission before power reaches the rear wheel. Changing these gears directly affects acceleration, cruising RPM, and maximum speed.

Factory Gear Ratio

• 13T / 40T = 3.076:1

NCY Performance Gear Ratio

• 15T / 38T = 2.533:1

A lower numerical gear ratio allows the rear wheel to travel farther with each engine revolution, resulting in:

• Higher top speed
• Lower cruising RPM
• Better highway performance
• More usable power from modified engines
• Improved overall riding comfort

The 15T/38T provides an excellent balance between acceleration and top-end performance, making it one of the most versatile gear upgrades available.

Higher Numerical Ratio (Example: Stock 3.076:1)

Advantages:

• Faster acceleration
• More rear wheel torque
• Better hill climbing
• Best for stock engines

Disadvantages:

• Higher cruising RPM
• Lower top speed

Lower Numerical Ratio (Example: NCY 2.533:1)

Advantages:

• Higher maximum speed
• Lower engine RPM while cruising
• Better use of added horsepower
• Smoother high-speed riding

Disadvantages:

• Slightly less mechanical leverage at low speeds
• Best suited for engines producing additional power

Stock 125cc–150cc Engines

Factory gearing is usually the best choice unless riding mostly on flat roads.

155cc–169cc Big Bore Builds

Excellent Choice: NCY 15T / 38T

Provides:

• Noticeable increase in top speed
• Comfortable cruising RPM
• Strong everyday acceleration

Perfect for:

• Mild performance builds
• Performance exhausts
• Variator upgrades
• Camshaft upgrades

171cc–180cc Performance Builds

The 15T/38T is an outstanding all-around street gear.

Works exceptionally well with:

• 61mm cylinders
• 63mm cylinders
• Stroker crankshafts
• Performance CVT systems

180cc–200cc+ High Performance Builds

Ideal for larger displacement engines producing increased horsepower.

Benefits include:

• Lower highway RPM
• Increased top speed
• Better use of engine power
• Improved long-distance cruising

Front Counter Shaft

• Teeth: 15
• Overall Length: 60mm
• Spline Length: 24mm
• Outside Diameter: 31.1mm

Gear Press-On Area

• Length: 12.08mm
• Outside Diameter: 19.08mm

Shaft Ends

• Length: 9–10.5mm
• Outside Diameter: 15mm

Rear Final Drive Gear

• Teeth: 38
• Spline Count: 19
• Outside Diameter: 71.2mm
• Inside Diameter: 18mm
• Width: 20mm

Huge Time-Saving Advantage

✔ Countershaft gear is professionally pre-pressed and assembled

✔ No 50-ton hydraulic press required

✔ No machine shop needed

✔ No extra labor costs

Simply reuse your factory 42-tooth countershaft gear during installation and enjoy a much easier installation process than standard gear kits.

Fits most GY6-based 125cc–200cc engines including:

• 157QMJ
• 152QMI
• 161QMK
• 1P61QMK
• YN1P57QMJ
• JJ157QMJ
• BN157QMJ
• BN161QMK-A
• 154FMI
• 1P52FMI
• 1P57QMJ

Also compatible with many other engines whose engine code contains QM, QMK, QMI, or FM.

NCY has been manufacturing premium scooter performance components in Taiwan since 1997 and is one of the industry's most respected names for drivetrain, suspension, and engine performance upgrades. Their ISO 9001-certified manufacturing ensures outstanding quality, durability, and precision.

Why Choose the 15T/38T?

Compared to the taller 15T/37T gear set, the 15T/38T offers a slightly more conservative 18% up gear, making it an excellent choice for riders who want increased top speed while maintaining stronger acceleration and better performance on hills. It's often considered the "sweet spot" for 155cc–180cc street builds, offering a great balance of speed, drivability, and everyday usability.