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Start ShoppingMIKUNI F4/042-190 Hex Main Jets - High-Performance Brass Fuel Jets for Powersports Engines
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Description
Upgrade your powersports engine's fuel delivery system with MIKUNI's F4/042-190 Hex Main Jets. These precision-engineered brass jets deliver optimal airflow and fuel mixture for enhanced power, responsiveness, and engine efficiency in high-performance applications.
Key Features
- Brass Construction: Durable, corrosion-resistant material ensures long-lasting performance in demanding off-road and racing environments.
- Hex Head Thread: Secure, tamper-proof fit for easy installation and precise fuel flow control.
- M5 x 0.75 Thread: Universal compatibility with most MIKUNI carburetor systems for seamless integration.
- 6mm Hex Head: Standard size for quick adjustments and maintenance without specialized tools.
- 0.5g Weight: Lightweight design minimizes rotational mass while maintaining structural integrity.
Why Choose This Product
These jets are engineered for riders who demand precision tuning and maximum performance. The brass material resists clogging and wear, while the hex thread ensures a leak-proof seal. Perfect for modifying 2-stroke and 4-stroke engines, these jets offer a balance of durability and responsiveness for track days, trail riding, and competitive racing scenarios.
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Upgrade your powersports engine's fuel delivery system with MIKUNI's F4/042-190 Hex Main Jets. These precision-engineered brass jets deliver optimal airflow and fuel mixture for enhanced power, responsiveness, and engine efficiency in high-performance applications.
Key Features
- Brass Construction: Durable, corrosion-resistant material ensures long-lasting performance in demanding off-road and racing environments.
- Hex Head Thread: Secure, tamper-proof fit for easy installation and precise fuel flow control.
- M5 x 0.75 Thread: Universal compatibility with most MIKUNI carburetor systems for seamless integration.
- 6mm Hex Head: Standard size for quick adjustments and maintenance without specialized tools.
- 0.5g Weight: Lightweight design minimizes rotational mass while maintaining structural integrity.
Why Choose This Product
These jets are engineered for riders who demand precision tuning and maximum performance. The brass material resists clogging and wear, while the hex thread ensures a leak-proof seal. Perfect for modifying 2-stroke and 4-stroke engines, these jets offer a balance of durability and responsiveness for track days, trail riding, and competitive racing scenarios.| SKU | GMA011679B |
|---|---|
| MPN | F4/042-190 |
| Brand | MIKUNI |
| Category | Jets |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Various | Mikuni TM/HVM series carburetors | 1980-2025 |
| Suzuki | RM250/DR-Z400 | 1990-2005 |
| Yamaha | YFS200 Blaster, YZ250 | 1985-2010 |
| Honda | CRF450R, XR400 | 1995-2020 |
Frequently Asked Questions
Fits Mikuni round main jet carbs like BS30/VM26-40, TM38-42 series. Check your carb's main jet type (hex head, #190 size).
#190 is larger than stock #160-180 on most trail bikes, used for richer mixtures at WOT or high altitude.
Sold individually for precise tuning. Buy 5-10 sizes for full rejetting.
Aftermarket tuning part; may affect emissions warranty but common for performance mods.
Use plug chop method or wideband O2 sensor. Start 5 sizes richer than stock and adjust.
Installation Guide
Difficulty
Easy
Est. Time
10 min
Tools Required
- Small flathead screwdriver
- 12-point socket or wrench (6mm)
Pro Tips
- Remove float bowl completely for access. Clean jet orifice with carb cleaner before install. Test multiple sizes for best tuning.
Common Mistakes to Avoid
- Installing backwards (flow direction matters)
- Not cleaning carb bowl before install
- Over-tightening jet
Comparison vs Stock/OEM
Direct replacement for OEM Mikuni or Keihin jets in many Japanese bikes
Improvements
- Precision machined brass for consistent flow
- Removable for easy sizing changes
- Corrosion resistant
Considerations
- Genuine Mikuni; avoid cheap knockoffs with inconsistent sizing
Durability & Warranty
Expected Lifespan
Indefinite with proper maintenance (carb cleaning)
Warranty
Limited lifetime from Mikuni against defects
Maintenance
Clean with carb cleaner every service; inspect for wear/clogging
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