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Start ShoppingMIKUNI F4/042-90 Hex Main Jets - High-Performance Brass Carburetor Jets for Powersports
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Description
Upgrade your powersports engine's fuel delivery system with these MIKUNI F4/042-90 Hex Main Jets. Engineered for precision performance, these brass jets deliver reliable fuel flow optimization for motorcycles, ATVs, and off-road vehicles.
Key Features
- Brass Construction: Durable, corrosion-resistant material ensures long-lasting performance in harsh environments.
- Hex Head Design: Easy-to-adjust hex head allows precise fuel flow tuning without specialized tools.
- 4/042 Series Compatibility: Perfect fit for MIKUNI carburetors requiring #90 main jet sizing.
- Exact Dimensions: M5 x 0.75 thread with 0.25" diameter head for precise installation.
Why Choose This Product
These main jets offer superior flow control for power delivery optimization. The brass material resists clogging and maintains consistent fuel metering under extreme conditions. Riders benefit from enhanced throttle response and engine efficiency, making them essential for competitive racing or high-performance street use. The hex design simplifies maintenance, while the precise sizing ensures compatibility with original equipment specifications.
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Upgrade your powersports engine's fuel delivery system with these MIKUNI F4/042-90 Hex Main Jets. Engineered for precision performance, these brass jets deliver reliable fuel flow optimization for motorcycles, ATVs, and off-road vehicles.
Key Features
- Brass Construction: Durable, corrosion-resistant material ensures long-lasting performance in harsh environments.
- Hex Head Design: Easy-to-adjust hex head allows precise fuel flow tuning without specialized tools.
- 4/042 Series Compatibility: Perfect fit for MIKUNI carburetors requiring #90 main jet sizing.
- Exact Dimensions: M5 x 0.75 thread with 0.25" diameter head for precise installation.
Why Choose This Product
These main jets offer superior flow control for power delivery optimization. The brass material resists clogging and maintains consistent fuel metering under extreme conditions. Riders benefit from enhanced throttle response and engine efficiency, making them essential for competitive racing or high-performance street use. The hex design simplifies maintenance, while the precise sizing ensures compatibility with original equipment specifications.| SKU | GM6441880D |
|---|---|
| MPN | F4/042-90 |
| Brand | MIKUNI |
| Category | Jets |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Various Japanese | Keihin/Mikuni carbureted motorcycles and ATVs | 1985-2024 |
Frequently Asked Questions
Fits Mikuni and Keihin carbs using 4/042 series main jets, common on 2-stroke and 4-stroke dirt bikes/ATVs from 1980s-2000s.
Yes, OEM-style hex main jet for precise fuel metering.
Check plug color after test ride or use jet kit calculator based on mods/elevation.
Hex jets are easier to remove/install without special tools.
Installation Guide
Difficulty
Easy
Est. Time
5 min
Tools Required
- Small flathead screwdriver
- Jet wrench or needle nose pliers
Pro Tips
- Remove carb from bike if possible for better access. Clean all parts and verify jet size with calipers.
Common Mistakes to Avoid
- Dropping jet into carb body
- Not cleaning float bowl before install
Comparison vs Stock/OEM
Direct OEM replacement or equivalent
Improvements
- Precision machined brass for consistent flow
- Hex head for easy tuning
Considerations
- None - matches factory specs
Durability & Warranty
Expected Lifespan
Indefinite with proper maintenance
Warranty
Manufacturer defect warranty, typically 1 year
Maintenance
Inspect/clean during carb service; replace if clogged or damaged
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