RCB E2 SERIES BRAKING SYSTEM
RCB S1 SERIES BRAKING SYSTEM
Recommended Additional Upgrades
03
Uma Racing Engine Oil
Get smoother engine performance with Uma Racing Full Synthetic Engine Oil.
UMA Racing High-Performance Clutch Spring Kit (4-Piece) is a premium, race-proven powertrain upgrade specifically engineered for the high-RPM engines of the Yamaha R15 V3, R15 V4, and R15M.
Designed to replace soft factory springs, this kit significantly increases clamping force on the clutch pack. It completely eliminates high-RPM clutch slippage, ensuring that every bit of your engine’s power is transferred directly to the rear wheel.
Key Features
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Premium Swedish Chrome-Silicon Steel Matrix: Manufactured from ultra-high-tensile chrome-silicon steel alloy. This professional-grade spring wire undergoes specialized heat treatment and shot-peening to ensure excellent fatigue resistance and prevent spring sagging over time.
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Enhanced High-RPM Clamping Force: Engineered to deliver a 10% to 15% increase in pressure loading over stock Yamaha springs. This added clamping force holds the friction plates firmly against the steel plates, preventing the clutch from slipping under hard acceleration or high-load conditions.
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Crisp, Definitive Lever Engagement: By replacing soft factory springs, this kit sharpens your lever feel. It provides a highly predictable, instantaneous engagement point (friction zone) that is ideal for rapid launches, track racing, and aggressive downshifts.
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Excellent Thermal Structural Stability: Standard clutch springs often soften and lose tension when subjected to intense engine heat during heavy track use or stop-and-go city traffic. The UMA Racing alloy matrix maintains uniform tension up to extreme operating temperatures, eliminating fading lever pressure.
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Perfect Assist & Slipper Clutch Integration: This 4-piece kit is precision-dimensioned to match the exact length, outer diameter, and coil pitch of Yamaha’s factory Assist & Slipper clutch hubs. It increases clamping force without interfering with the smooth operation of the slipper mechanism during hard downshifts.
Technical Specifications
| Feature | UMA Racing Clutch Spring Set Details |
| Product Line | UMA Performance Powertrain Series |
| Spring Count | 4 Pieces (Complete Engine Set) |
| Material Base | High-Tensile Heat-Treated Chrome-Silicon Alloy |
| Pressure Upgrade | ~10% to 15% Stiffer Over OEM Specification |
| Primary Compatibility | Yamaha R15 V3 (VVA) / R15 V4 / R15M |
| Shared Engine Platform | Yamaha MT-15 / XSR155 / WR155R |
| Performance Profile | Eliminates High-RPM Slip, Harder Launch Traction |
Shared Engine Compatibility
Because Yamaha shares its high-performance 155cc Liquid-Cooled VVA engine across several platforms, this 4-spring kit drops directly into the following models:
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Yamaha R15 V3 / V4 / R15M (All years)
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Yamaha MT-15 (Hyper-naked variant)
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Yamaha XSR155 (Neo-retro variant)
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Yamaha WR155R (Dual-sport variant – significantly improves off-road hill climbing torque traction)
Step-by-Step Installation Guidelines
To prevent cracking the delicate aluminum pressure plate or causing uneven clutch engagement, follow this professional installation sequence:
Rider Comfort Note: Because these high-performance racing springs increase clamping force inside the engine, you will experience a slightly firmer pull at the handlebar clutch lever. This is entirely normal and ensures maximum power transfer to the ground.
