Recommended Additional Upgrades
01
Uma Laser Iridium Spark Plug
Improve ignition with Uma Racing Laser Iridium Spark Plug.
03
Uma Racing Engine Oil
Get smoother engine performance with Uma Racing Full Synthetic Engine Oil.
The UMA Racing Torque Spring (1500RPM – Purple) is a high-tension CVT component designed for aggressive performance. While the 1000RPM Red spring is for “Sport Street” use, the 1500RPM Purple spring is engineered for Racing, Drag, or Big Bore builds (like 62mm/63mm setups).
Its primary job is to provide heavy pressure on the rear pulley, forcing the engine to stay at a higher RPM range where the most power is produced.
Key Performance Benefits
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Extreme Back-Shift: This spring is very “stiff.” When you let go of the throttle and snap it back open, the transmission downshifts almost instantly, providing an explosive surge of power.
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Zero Belt Slip: Ideal for high-torque engines. It clamps the CVT belt with significantly more force than stock, ensuring that every bit of horsepower from the engine actually reaches the rear wheel without “slop.”
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High-RPM Bias: It prevents the CVT from “upshifting” too early. This keeps the engine screaming in its power band (useful if you have a racing camshaft that makes power at high RPMs).
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Anti-Fatigue Material: Made from premium alloy steel that maintains its “rebound” even under the intense heat generated during racing or long-distance high-speed sprints.
Technical Specifications
| Feature | UMA 1500RPM Torque Spring Details |
| Rating | 1500 RPM (High Tension) |
| Color | Purple (Newer UMA high-tension coding) |
| Compatibility | Yamaha Aerox 155 (V1/V2), NMAX 155 (V1/V2), NVX 155 |
| Material | Silicon Manganese Steel |
1000RPM vs. 1500RPM: The Trade-off
| Tension | Acceleration | Top Speed | Fuel Economy |
| 1000RPM (Red) | Improved | Usually Maintained | Minimal Impact |
| 1500RPM (Purple) | Violent/Instant | May Drop Slightly* | Decreased |
Crucial Note: On a completely stock engine, a 1500RPM spring might actually make the bike slower. If the engine doesn’t have enough power to “fight” the spring and push the belt to the outer edge of the pulley, you will lose top speed and your engine will vibrate excessively from high RPMs.
Tuning Recommendation: Roller Weights
To balance the high tension of the Purple 1500RPM spring, you must carefully select your roller weights:
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Heavy Rollers: If you find the engine is “screaming” but the bike isn’t moving fast (overshooting the power band), you need to increase your roller weight.
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The Setup: This spring is most effective when paired with a 62mm/63mm Block, a Racing ECU, and the UMA High Speed Pulley.
Installation Tip
When installing such a stiff spring, ensure your secondary sliding sheave (the rear pulley) is in good condition. The extra pressure can accelerate wear on cheap or unlubricated torque cam pins. Use high-quality CVT grease during the install.
FAQs
Is 1500RPM better than 1000RPM?
For stronger acceleration and sportier feel, yes. For softer daily riding, 1000RPM may feel smoother.
Will it reduce top speed?
Usually depends on full CVT setup. Proper roller tuning is important.
Good for stock scooter?
Yes, but best results come with pulley/roller tuning.
