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Start ShoppingMIKUNI Large Round Main Jet 137.5 - Precision Fuel Control for High-Performance Engines
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Description
Optimize your engine's mid-range to full-throttle performance with this MIKUNI Large Round Main Jet. Engineered for precision fuel delivery, this critical component ensures smooth power delivery and efficient combustion in high-output powersports engines.
Key Features
- 137.5mm Size: Precisely calibrated for optimal fuel flow in mid-range to full-throttle operation.
- Large Round Shape: Ensures consistent fuel metering and reduces clogging in demanding conditions.
- Brass Construction: Durable, corrosion-resistant material for long-lasting performance in harsh environments.
- Direct Replacement Compatibility: Designed to fit standard Mikuni carburetor systems for seamless installation.
Why Choose This Product
Upgrade your engine's fuel delivery system with a Mikuni main jet engineered for reliability and precision. The large round design minimizes flow restrictions while maintaining accurate fuel metering. Brass construction resists wear and corrosion, ensuring consistent performance through thousands of miles of use. This critical component is essential for riders seeking peak power output and smooth throttle response in high-performance engines.
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Optimize your engine's mid-range to full-throttle performance with this MIKUNI Large Round Main Jet. Engineered for precision fuel delivery, this critical component ensures smooth power delivery and efficient combustion in high-output powersports engines.
Key Features
- 137.5mm Size: Precisely calibrated for optimal fuel flow in mid-range to full-throttle operation.
- Large Round Shape: Ensures consistent fuel metering and reduces clogging in demanding conditions.
- Brass Construction: Durable, corrosion-resistant material for long-lasting performance in harsh environments.
- Direct Replacement Compatibility: Designed to fit standard Mikuni carburetor systems for seamless installation.
Why Choose This Product
Upgrade your engine's fuel delivery system with a Mikuni main jet engineered for reliability and precision. The large round design minimizes flow restrictions while maintaining accurate fuel metering. Brass construction resists wear and corrosion, ensuring consistent performance through thousands of miles of use. This critical component is essential for riders seeking peak power output and smooth throttle response in high-performance engines.| SKU | GM865A42D6 |
|---|---|
| MPN | FN100604-137.5 |
| Brand | MIKUNI |
| Category | Jets |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Universal | Mikuni VM, TM, HSR series carburetors | 1980-2025 |
| Honda | CRF450R, CRF250R | 1997-2024 |
| Yamaha | YZ450F, YZ250F, WR450F | 2000-2024 |
| Kawasaki | KX450F, KX250F | 1999-2024 |
Frequently Asked Questions
The main jet controls fuel flow through the main fuel circuit at mid-range to full throttle operation. Larger jets (higher numbers) allow more fuel, while smaller jets restrict fuel flow. Proper jetting is critical for engine performance and reliability.
Jet size depends on your specific carburetor model, engine displacement, altitude, and intended use. Consult your carburetor manual, engine manufacturer specifications, or contact a Mikuni dealer. The 137.5 size is a mid-range main jet suitable for various small to mid-displacement engines.
No. Different Mikuni carburetor models have different jet configurations. Verify your carburetor model number and ensure this jet is compatible. Using an incorrect jet can cause poor engine performance or damage.
Main jets rarely need replacement unless damaged or clogged. They typically last the life of the carburetor. Replace only if you're changing jetting for tuning purposes or if the jet is damaged.
Pilot jets control fuel at idle and low throttle operation, while main jets control fuel at mid-range to full throttle. Both are needed for proper carburetor function across the entire throttle range.
Installation Guide
Difficulty
Easy
Est. Time
15 min
Tools Required
- Small screwdriver (Phillips or flat head)
- Carburetor removal tools (varies by application)
- Clean workspace
- Gasket scraper or soft brush
Pro Tips
- Take photos during disassembly for reference
- Keep carburetor bowl gasket clean and replace if damaged
- Test run engine after installation to verify proper jetting
- Keep spare jets on hand for tuning adjustments
- Consult carburetor manual for exact jet location and specifications
Common Mistakes to Avoid
- Over-tightening jet (can strip brass threads)
- Installing jet upside down
- Not cleaning carburetor bowl before reassembly
- Failing to verify correct jet size for application
- Not checking fuel line condition while carburetor is removed
Durability & Warranty
Expected Lifespan
Indefinite under normal use (brass component resistant to corrosion)
Warranty
Typically covered under Mikuni's standard warranty (verify with retailer)
Maintenance
No maintenance required; replace only if damaged or for tuning purposes
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