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Start ShoppingMIKUNI F4/042-660 Hex Main Jets - Precision Fuel Delivery for High-Performance Engines
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Description
Upgrade your engine's fuel delivery system with MIKUNI's F4/042-660 Hex Main Jets, engineered for precision and performance. These jets ensure consistent fuel flow, enhancing power output and throttle response for a wide range of powersports applications.
Key Features
- Hexagonal Design: Ensures secure fitment and easy adjustment for precise fuel metering.
- High-Quality Alloy: Durable construction resists corrosion and maintains accuracy under extreme conditions.
- Universal Compatibility: Designed to work with MIKUNI carburetor systems for seamless integration.
- Performance Optimization: Fine-tunes air-fuel ratios for improved horsepower and fuel efficiency.
Why Choose This Product
MIKUNI jets are trusted by racers and mechanics worldwide for their reliability and precision. These main jets deliver consistent fuel flow, reducing engine hesitation and maximizing power output. Whether you're tuning a motorcycle, ATV, or UTV, the F4/042-660 provides the accuracy needed for peak performance. The hex design simplifies installation and adjustment, saving time during maintenance or customization projects.
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Upgrade your engine's fuel delivery system with MIKUNI's F4/042-660 Hex Main Jets, engineered for precision and performance. These jets ensure consistent fuel flow, enhancing power output and throttle response for a wide range of powersports applications.
Key Features
- Hexagonal Design: Ensures secure fitment and easy adjustment for precise fuel metering.
- High-Quality Alloy: Durable construction resists corrosion and maintains accuracy under extreme conditions.
- Universal Compatibility: Designed to work with MIKUNI carburetor systems for seamless integration.
- Performance Optimization: Fine-tunes air-fuel ratios for improved horsepower and fuel efficiency.
Why Choose This Product
MIKUNI jets are trusted by racers and mechanics worldwide for their reliability and precision. These main jets deliver consistent fuel flow, reducing engine hesitation and maximizing power output. Whether you're tuning a motorcycle, ATV, or UTV, the F4/042-660 provides the accuracy needed for peak performance. The hex design simplifies installation and adjustment, saving time during maintenance or customization projects.
| SKU | GMAA080A6B |
|---|---|
| MPN | F4/042-660 |
| Brand | MIKUNI |
| Category | Jets |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Various (universal carbureted powersports) | Mikuni VM/PF/BS series carbs (e.g., VM34, BS34) | 1980-2025 |
| Honda | XR series (XR250R, XR400R, XR650R) | 1990-2010 |
| Yamaha | XT/TT series (XT250, TT-R250) | 1985-2005 |
Frequently Asked Questions
Fits Mikuni round/hex main jets for VM, BS, HSR, PJ series carbs on most 2-stroke/4-stroke dirt bikes and ATVs.
Use a main jet kit or dyno tune; start with stock size and adjust based on plug reads (leaner = smaller number, richer = larger).
Yes, OEM Mikuni part number F4/042-660.
No, this is for carbureted engines only.
Installation Guide
Difficulty
Easy
Est. Time
5 min
Tools Required
- Small flathead screwdriver
- Jet wrench or hex key (optional)
Pro Tips
- Remove float bowl, unscrew old jet counterclockwise, note size of stock jet. Clean new jet before install. Test plug chop after changes.
Common Mistakes to Avoid
- Not cleaning carb passages before install
- Incorrect jet sizing without testing
Comparison vs Stock/OEM
Direct OEM replacement or upgrade for worn jets; identical to factory Mikuni jets
Improvements
- Precise fuel delivery for optimal performance
- Corrosion-resistant brass construction
Considerations
- Must match exact size to avoid lean/rich conditions
Durability & Warranty
Expected Lifespan
Engine life (5+ years with proper tuning); replace if clogged or worn
Warranty
Mikuni lifetime defect warranty
Maintenance
Inspect during carb cleans (every 10-20 hours riding); clean with carb cleaner
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