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Start ShoppingMIKUNI Hex Main Jet #680 - Precision Brass Fuel Jet for High-Performance Engines
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Description
Upgrade your Mikuni carburetor's fuel delivery system with this precision-machined brass hex main jet. Designed for #680 fuel flow rates, this essential component ensures consistent performance across a range of powersports applications, from racing to daily commuting.
Key Features
- Brass Construction: Durable, corrosion-resistant material withstands high temperatures and fuel exposure
- #680 Jet Size: Optimized flow rate for balanced power delivery and fuel efficiency
- Hex Head Design: Simplifies installation with standard Mikuni threading for quick, secure fitting
- Lightweight Build: Only 0.1 oz adds negligible weight to your carburetor system
- Universal Compatibility: Works with most Mikuni carburetor models for easy replacement
Why Choose This Product
Whether you're tuning a high-performance racing bike or maintaining a street motorcycle, this hex main jet delivers reliable fuel flow with minimal maintenance. The brass construction resists wear from fuel additives, while the hex head design eliminates the need for specialized tools during installation. Its precise #680 sizing ensures optimal air-fuel ratios, helping riders achieve better throttle response and fuel economy without compromising engine performance.
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Upgrade your Mikuni carburetor's fuel delivery system with this precision-machined brass hex main jet. Designed for #680 fuel flow rates, this essential component ensures consistent performance across a range of powersports applications, from racing to daily commuting.
Key Features
- Brass Construction: Durable, corrosion-resistant material withstands high temperatures and fuel exposure
- #680 Jet Size: Optimized flow rate for balanced power delivery and fuel efficiency
- Hex Head Design: Simplifies installation with standard Mikuni threading for quick, secure fitting
- Lightweight Build: Only 0.1 oz adds negligible weight to your carburetor system
- Universal Compatibility: Works with most Mikuni carburetor models for easy replacement
Why Choose This Product
Whether you're tuning a high-performance racing bike or maintaining a street motorcycle, this hex main jet delivers reliable fuel flow with minimal maintenance. The brass construction resists wear from fuel additives, while the hex head design eliminates the need for specialized tools during installation. Its precise #680 sizing ensures optimal air-fuel ratios, helping riders achieve better throttle response and fuel economy without compromising engine performance.| SKU | GM1072DF7C |
|---|---|
| MPN | F4/042-680 |
| Brand | MIKUNI |
| Category | Jets |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Various Yamaha | XT series (e.g., XT250, XT350) | 1980-2025 |
| Various Kawasaki | KX series (e.g., KX250, KX500) | 1970-2000 |
| Various Honda | XR series (e.g., XR250R, XR400R) | 1985-2010 |
| Suzuki | DR-Z400 | 1990-2020 |
| All Years |
Frequently Asked Questions
Fits Mikuni VM26-VM44, TM38-TM42, and HSR42 round-slide carbs on most 125-500cc dirt bikes and ATVs.
Jet size depends on engine mods, altitude, and temp. Use a jet kit chart or dyno tune; #680 is large, suited for high-flow setups or sea level.
Hex jets have wrench flats for easier removal without special tools or pliers that can damage them.
No, Mikuni jets have different threading; confirm carb model first.
Installation Guide
Difficulty
Easy
Est. Time
5 min
Tools Required
- Small flathead screwdriver
- Jetting gauge or calipers (optional)
Pro Tips
- Remove carb bowl completely for access. Always verify jet size stamped on side. Clean with carb cleaner, not compressed air alone.
Common Mistakes to Avoid
- Not cleaning carb passages before install
- Incorrect jet size selection for altitude/temp
Comparison vs Stock/OEM
Aftermarket Mikuni jet vs OEM (often round soft brass)
Improvements
- Hex head prevents rounding/stripping
- More precise machining for consistent flow
- Easier tuning without special tools
Considerations
- Must match carb type; not direct OEM swap in all cases
Durability & Warranty
Expected Lifespan
Indefinite with proper cleaning; does not wear out
Warranty
Limited lifetime from Mikuni against defects
Maintenance
Remove and clean during every carb service (every 10-20 hours off-road)
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