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Start ShoppingMIKUNI F4/042-400 Hex Main Jets - High-Performance Brass Carburetor Jets for Powersports
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Description
Upgrade your powersports engine's fuel delivery system with MIKUNI's F4/042-400 Hex Main Jets. These precision-engineered brass jets ensure accurate fuel metering for maximum power, efficiency, and responsiveness in motorcycles, ATVs, and off-road vehicles.
Key Features
- Brass Construction: Durable, corrosion-resistant material for long-lasting performance in harsh environments.
- #400 Jet Size: Optimized flow rate for high-performance engines requiring precise fuel-air mixture control.
- Hex Head Thread: 5/16-32 thread pattern ensures secure, leak-free installation in compatible carburetor systems.
- Compact Design: 0.5" length and 0.3125" diameter for easy handling and precise fitment.
- Lightweight: Under 1 gram for minimal impact on engine balance and performance.
Why Choose This Product
MIKUNI jets are trusted by racers and enthusiasts for their reliability and precision. The hex thread design simplifies installation while maintaining a secure connection. Brass's thermal conductivity ensures consistent fuel flow across temperature ranges, while the #400 size delivers optimal performance for high-output engines. Whether you're tuning a sport bike or off-road vehicle, these jets provide the accuracy needed for peak power and smooth throttle response.
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Upgrade your powersports engine's fuel delivery system with MIKUNI's F4/042-400 Hex Main Jets. These precision-engineered brass jets ensure accurate fuel metering for maximum power, efficiency, and responsiveness in motorcycles, ATVs, and off-road vehicles.
Key Features
- Brass Construction: Durable, corrosion-resistant material for long-lasting performance in harsh environments.
- #400 Jet Size: Optimized flow rate for high-performance engines requiring precise fuel-air mixture control.
- Hex Head Thread: 5/16-32 thread pattern ensures secure, leak-free installation in compatible carburetor systems.
- Compact Design: 0.5" length and 0.3125" diameter for easy handling and precise fitment.
- Lightweight: Under 1 gram for minimal impact on engine balance and performance.
Why Choose This Product
MIKUNI jets are trusted by racers and enthusiasts for their reliability and precision. The hex thread design simplifies installation while maintaining a secure connection. Brass's thermal conductivity ensures consistent fuel flow across temperature ranges, while the #400 size delivers optimal performance for high-output engines. Whether you're tuning a sport bike or off-road vehicle, these jets provide the accuracy needed for peak power and smooth throttle response.
| SKU | GM692A78F5 |
|---|---|
| MPN | F4/042-400 |
| Brand | MIKUNI |
| Category | Jets |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Various (Universal) | Mikuni TM/HVM/PF/VM series carburetors | 1980-2025 |
Frequently Asked Questions
Fits Mikuni TM, HVM, PFN, and VM series carbs with round main jet position. Confirm your carb model and stock jet size.
#400 is a large size, typically for high-altitude or very rich tuning. Most stock jets are #100-150; measure yours first.
Often yes - changing main jet may require pilot jet, needle, or air screw adjustment for proper fueling across throttle range.
No, Mikuni jets have different threading. Keihin uses BS30/VM jets.
Installation Guide
Difficulty
Easy
Est. Time
5 min
Tools Required
- Small flathead screwdriver
- Jet wrench or needle nose pliers
Pro Tips
- Remove carb bowl completely for access. Clean jet orifice with carb cleaner and compressed air. Always test plug color after install to verify tuning.
Common Mistakes to Avoid
- Not cleaning carb passages before install
- Incorrect jet size selection causing lean/rich conditions
Comparison vs Stock/OEM
Direct OEM replacement or performance upgrade for worn jets
Improvements
- Precise fuel metering for better throttle response
- Consistent flow from quality brass machining
Considerations
- Aftermarket identical to OEM specs; choose size based on mods/exhaust/air filter
Durability & Warranty
Expected Lifespan
Indefinite with proper tuning (jets rarely wear out)
Warranty
Limited lifetime from Mikuni against manufacturing defects
Maintenance
Inspect/clean during carb service (every 20-50 hours). Replace if orifice deformed.
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