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Start ShoppingMIKUNI F4/042-620 Hex Main Jets - Precision Fuel Delivery for High-Performance Engines
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Description
Upgrade your MIKUNI carburetor with these high-precision hex main jets designed to deliver perfect fuel-air ratios for maximum power and efficiency. Ideal for riders seeking reliable performance across a range of engine conditions.
Key Features
- Hexagonal Design: Ensures secure fitment and precise fuel flow control for consistent engine performance.
- High-Quality Material: Durable brass construction resists corrosion and maintains accuracy under extreme operating conditions.
- Easy Installation: Standardized sizing simplifies replacement without requiring specialized tools.
- Performance Optimization: Fine-tuned orifice sizes deliver optimal fuel delivery for improved throttle response and power output.
Why Choose This Product
These main jets are engineered for riders who demand precision and reliability from their powersports equipment. By maintaining the correct fuel-air mixture, they help prevent engine knocking, reduce emissions, and extend engine life. The hex design ensures accurate adjustment while minimizing the risk of clogging, making them a trusted choice for both street and off-road applications.
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Upgrade your MIKUNI carburetor with these high-precision hex main jets designed to deliver perfect fuel-air ratios for maximum power and efficiency. Ideal for riders seeking reliable performance across a range of engine conditions.
Key Features
- Hexagonal Design: Ensures secure fitment and precise fuel flow control for consistent engine performance.
- High-Quality Material: Durable brass construction resists corrosion and maintains accuracy under extreme operating conditions.
- Easy Installation: Standardized sizing simplifies replacement without requiring specialized tools.
- Performance Optimization: Fine-tuned orifice sizes deliver optimal fuel delivery for improved throttle response and power output.
Why Choose This Product
These main jets are engineered for riders who demand precision and reliability from their powersports equipment. By maintaining the correct fuel-air mixture, they help prevent engine knocking, reduce emissions, and extend engine life. The hex design ensures accurate adjustment while minimizing the risk of clogging, making them a trusted choice for both street and off-road applications.
| SKU | GMDF0EFED0 |
|---|---|
| MPN | F4/042-620 |
| Brand | MIKUNI |
| Category | Jets |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Various (Yamaha, Honda, Suzuki, Kawasaki) | Multiple 2-stroke and 4-stroke carbureted models | 1980-2025 |
Frequently Asked Questions
Fits most Mikuni round-slide carbs like VM26-VM40, TM series, HSR42/45, and BS30/34/36/38/40.
Universal for both; size 620 is common for larger displacement bikes/ATVs needing richer mid-to-high RPM fueling.
Use plug reading, EGT gauge, or wideband O2 sensor; start with OEM size and adjust ±5 sizes based on mods like exhaust/air filter.
No, Mikuni jets have different threading/taper; use Keihin jets for Keihin carbs.
Installation Guide
Difficulty
Easy
Est. Time
10 min
Tools Required
- Small flathead screwdriver
- Jet cleaning wire or compressed air
Pro Tips
- Remove float bowl completely for access; note original jet size before replacement; test plug chop after install to verify mixture
Common Mistakes to Avoid
- Not cleaning carb passages before install
- Installing wrong jet size without re-jetting map
Comparison vs Stock/OEM
Direct OEM replacement or upgrade; identical to factory Mikuni jets on many Japanese bikes
Improvements
- Precision machined for consistent flow
- Pure brass for corrosion resistance
- Easier hex head for tool-free removal
Considerations
- Aftermarket identical to OEM in most cases
Durability & Warranty
Expected Lifespan
Engine rebuild or 5+ years with proper cleaning
Warranty
Limited lifetime by Mikuni against defects
Maintenance
Clean with carb cleaner every 10-20 hours; avoid harsh solvents that strip plating
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