UMA Racing Timing Chain Gear for Yamaha MT/ R15 V3/ V4 - 02TG0040
UMA Racing Timing Chain Gear for Yamaha MT/ R15 V3/ V4 - 02TG0040
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The UMA Racing Timing Chain Gear (02TG0040) is a high-performance engine component specifically designed for the Yamaha R15 V3, R15 V4, and MT-15 (VVA platform).
Similar to other gears in the UMA performance lineup, this unit is an essential upgrade for high-compression engine builds, combining an adjustable timing gear with an integrated decompression mechanism to ensure both performance and reliability.
Key Technical Specifications
| Feature | Specification | Impact |
| Model Code | 02TG0040 | Calibrated for the Yamaha 155cc VVA platform. |
| Material | High-Grade Carbon Steel | Provides exceptional durability and high-load wear resistance. |
| Mechanism | Integrated Decompression | Lowers the physical effort required to crank the engine. |
| Timing Range | Adjustable (+/- 5°) | Allows for fine-tuning the power delivery to your preference. |
| Compatibility | Yamaha R15 V3/V4, MT-15, WR155 | Designed for the 155cc liquid-cooled engine. |
Core Performance Benefits
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Smooth Engine Startup: The primary advantage of the 02TG0040 is its pressure-reducing mechanism. In high-compression setups (like those with UMA 62mm or 63mm bore kits), the stock starter often struggles to turn the engine. This gear bleeds off excess pressure during the initial crank for an effortless start.
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Protection for Starter Components: By reducing the cranking load, this gear prevents premature burnout of your starter motor, sprag clutch, and battery, significantly increasing the reliability of a modified bike.
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Powerband Customization: The adjustable timing gear gives you the flexibility to shift where your bike makes its power.
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Advancing the timing shifts power lower in the RPM range for better off-the-line acceleration.
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Retarding the timing can improve top-end over-rev, helping you reach higher peak speeds on the track.
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VVA Synchronization: Specifically engineered to work with Yamaha's Variable Valve Actuation (VVA), ensuring that the timing transition between the low-speed and high-speed cam lobes remains seamless.
Installation and Tuning Note
This is a precision component that requires accurate Top Dead Center (TDC) alignment. Because it involves the timing chain and valve train, it is highly recommended to have it installed by a technician experienced with Yamaha VVA engines.
Pro-Tip: If you are building a "Stage 2" engine, consider pairing this gear with a UMA Racing Performance Camshaft and a high-flow Timing Chain (96L) to ensure the entire valve train is optimized for high RPMs.
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