Fine-tune your GY6's final drive ratio with an NCY 14-tooth Counter Shaft Gear Wheel. Available in three driven gear options — 36, 37, or 38 teeth — this single gear change lets you shift the balance between top speed and off-the-line acceleration without splitting the cases. Fits both A-block (54mm) and B-block (57mm) GY6 engine families. ISO 9001 certified and made in Taiwan by NCY since 1997.
Choosing Your Gear Ratio
The stock GY6 150cc final drive is typically a 14?40 combination. Swapping the driven gear changes the ratio and shifts the power delivery:
| Gear Option |
Ratio vs. Stock 14?40 |
Effect |
| 14?36 |
Shorter (numerically lower) |
Higher top speed, reduced low-end torque and acceleration. Best for flat roads and top-speed builds. |
| 14?37 |
Slightly shorter than stock |
Balanced upgrade — modest top speed gain with minimal sacrifice in acceleration. Good all-around street tune. |
| 14?38 |
Close to stock |
Near-stock ratio with slightly improved top speed over a 40T gear. Ideal for mild tuning or replacing a worn gear. |
Tip: Going to a lower tooth count (36T) raises top speed but means your engine will be spinning closer to its rev limit at speed. Pair with a big bore kit or performance exhaust to make the most of the taller ratio. If you just want a mild bump in top speed without sacrificing rideability, the 37T or 38T is the safer choice.
Fits GY6 157QMJ-based 125cc, 150cc, and 169cc engines with the following engine codes:
| Engine Code |
Engine Code |
Engine Code |
Engine Code |
| 157QMJ |
161QMK |
152QMI |
1P61QMK |
| YN1P57QMJ |
1P52FMI |
154FMI |
JJ157QMJ |
| 1P57QMJ |
BN157QMJ |
BN161QMK-A |
Other QMJ / QMK / QMI |
Don't see your engine code? If your engine code contains "QM" or "FM", this gear is likely compatible with your vehicle.
This product is intended for off-road use only and is not legal for use in California on pollution-controlled vehicles. Check local laws before installing.
California Prop 65 Warning: www.p65warnings.ca.gov
