Yamaha SR500 TT500 XT500 | TM40-6 Mikuni Flatslide Carburetor Kit | Pumper Kit

The Mikuni TM40-6 Flatslide Pumper Carburetor Kit makes hitting high speeds effortless—say goodbye to hard starting, hesitation, bogging, and flat spots forever. This genuine Mikuni TM40-6 with built-in accelerator pump (pumper) is perfectly sized and engineered for high-performance Yamaha 500cc singles, including the SR500, TT500, and XT500 models.

It installs as a direct replacement for the stock inlet snorkel (or manifold boot), with the included outlet mounting flange shifting the carb slightly forward to ensure proper clearance from the frame and surrounding components. Most Yamaha OEM push/pull throttle cables are compatible, but the kit includes new throttle cables plus a convenient 1/4-turn quick-action throttle for faster, more precise control. A built-in hose tail connects seamlessly to vacuum-operated fuel taps.

The carb comes pre-jetted with the ideal pilot, main, and accelerator pump nozzle settings optimized for Yamaha 500cc singles, plus spare jets for fine-tuning the main circuit during wide-open throttle testing. Adjustments account for real-world variables like climate, altitude, fuel octane variations, and engine mods (cam, exhaust, head porting, etc.).

Key Benefits

• Instant, crisp throttle response with no lag or lean spots—thanks to the pumper system.
• Smoother acceleration, stronger mid-range pull, and noticeable gains in horsepower and torque.
• In multiple dyno-tested cases on OEM-equipped engines, performance improvements of 25% or more (gains vary with setup and mods).
• Reliable starting, better part-throttle manners, and overall enhanced rideability—perfect for vintage thumpers, trail riders, cafe builds, or high-performance singles.

This flatslide carb delivers superior airflow and atomization compared to stock round-slide Mikuni VM carbs (common on these models), making it a go-to upgrade for anyone chasing more power and responsiveness without major engine work.

Installation is straightforward for most, with the included flange handling clearance issues. Fine-tune as needed for your specific bike—many report excellent out-of-the-box results.