Recommended Additional Upgrades
03
Uma Laser Iridium Spark Plug
Improve ignition with Uma Racing Laser Iridium Spark Plug.
The UMA Racing V1 Injector (240cc – 4 Hole) is a high-flow performance component designed for the Yamaha 155cc VVA engine family. While the stock injector is designed to deliver just enough fuel for the factory 155cc displacement, this 240cc unit is built to feed heavily modified engines that require a much higher volume of fuel to maintain a safe Air-Fuel Ratio (AFR).
This injector is typically reserved for “Monster” builds, such as 63mm bore kits or forced induction setups.
Key Features
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240cc Flow Rate: This is a massive jump from the stock flow (which is typically around 140cc–160cc). It ensures that even at high RPMs and Wide Open Throttle (WOT), the engine does not “run lean” and melt the piston.
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4-Hole Spray Pattern: Unlike some “racing” injectors that use 10 or 12 tiny holes, the 4-hole V1 is designed for a specific spray velocity. The larger holes help prevent clogging and provide a “heavy” mist that is ideal for high-displacement cylinders.
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Plug-and-Play Connector: Specifically designed to fit the factory wiring harness of the R15 V3/V4, MT-15, and XSR 155. No cutting or splicing of wires is required.
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Fast Response Solenoid: Built with high-quality internal coils that can open and close rapidly, allowing the ECU to maintain precise fuel control even past 12,000 RPM.
Technical Specifications
| Feature | UMA V1 240cc Injector Details |
| Flow Rate | 240cc/min |
| Nozzle Type | 4-Hole |
| Compatibility | R15 V3/V4/M, MT-15, XSR 155, WR155R |
| Engine Type | Liquid-Cooled 155cc–200cc+ VVA |
| Color Coding | Usually identified by a specific connector color (check packaging) |
Is 240cc too much for your bike?
Choosing an injector is about balance. If the injector is too big for your modifications, the bike will “drown” in fuel, idle poorly, and smoke.
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Stock 155cc / 58mm Block: Avoid this. A 240cc injector is far too large for a stock engine. It will cause extreme “rich” running and potential engine flooding.
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62mm / 63mm (183cc) Block: This injector is often considered the “upper limit.” It works well if you are using a Superhead with large valves and a racing cam, but might be overkill for a simple street bore-up.
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65mm+ / Stroker / Turbo Builds: This is the perfect application. At these levels of modification, the engine needs the 240cc capacity to prevent engine knock and overheating at high speeds.
Critical Requirement: Programmable ECU
You cannot install a 240cc injector on a stock Yamaha ECU. The stock computer will not know how to shorten the “injector pulse width” to compensate for the massive increase in flow.
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Must use: UMA M5, M9, or Aracer ECU.
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Tuning: You will need a professional dyno tune or an “Autotune” module to recalibrate the fuel map for this specific flow rate.
Installation Pro-Tip
When installing, always apply a tiny amount of clean engine oil or silicone grease to the O-rings. This prevents the rubber from tearing as you press the injector into the fuel rail, ensuring there are no dangerous high-pressure fuel leaks.
FAQs
Do I need ECU tuning after installing this?
Yes, strongly recommended. Larger injectors usually need fueling recalibration for best results.
Is 240CC good for stock bike?
Usually intended for modified setups. For stock bikes, it may be oversized without tuning.
What does 4-hole injector mean?
It refers to multi-hole spray nozzles designed for finer fuel atomization and improved mixture distribution.
