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Start ShoppingMIKUNI F4/042-140 Hex Main Jets - Precision Brass Carburetor Jets for High-Performance Engines
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Description
Upgrade your carburetor's fuel delivery system with MIKUNI's F4/042-140 Hex Main Jets. These precision-engineered brass jets deliver consistent airflow and fuel mixture for optimal engine performance, whether you're racing or riding recreationally.
Key Features
- Brass Construction: Durable, corrosion-resistant material ensures long-lasting performance in harsh engine environments.
- #140 Jet Size: Precisely calibrated for balanced fuel-air ratios in high-output engines.
- Hex Head Thread: 5/16-24 thread pattern ensures secure, leak-free installation in carburetor systems.
- Compact Design: 0.5" length and 0.375" hex width fit standard carburetor housings without modification.
- Lightweight Build: Just 0.1 oz (3 grams) reduces engine load while maintaining structural integrity.
Why Choose This Product
MIKUNI jets are trusted by professionals for their accuracy and reliability. The hex design simplifies adjustment while preventing accidental loosening during operation. The brass alloy resists clogging and maintains flow consistency across temperature extremes. Whether you're fine-tuning a sport bike or optimizing a classic engine, these jets provide the precision needed for peak performance.
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Upgrade your carburetor's fuel delivery system with MIKUNI's F4/042-140 Hex Main Jets. These precision-engineered brass jets deliver consistent airflow and fuel mixture for optimal engine performance, whether you're racing or riding recreationally.
Key Features
- Brass Construction: Durable, corrosion-resistant material ensures long-lasting performance in harsh engine environments.
- #140 Jet Size: Precisely calibrated for balanced fuel-air ratios in high-output engines.
- Hex Head Thread: 5/16-24 thread pattern ensures secure, leak-free installation in carburetor systems.
- Compact Design: 0.5" length and 0.375" hex width fit standard carburetor housings without modification.
- Lightweight Build: Just 0.1 oz (3 grams) reduces engine load while maintaining structural integrity.
Why Choose This Product
MIKUNI jets are trusted by professionals for their accuracy and reliability. The hex design simplifies adjustment while preventing accidental loosening during operation. The brass alloy resists clogging and maintains flow consistency across temperature extremes. Whether you're fine-tuning a sport bike or optimizing a classic engine, these jets provide the precision needed for peak performance.
| SKU | GM38166D2C |
|---|---|
| MPN | F4/042-140 |
| Brand | MIKUNI |
| Category | Jets |
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Featured Review
| Make | Model | Years |
|---|---|---|
| Various | Mikuni TM/VM series carbureted motorcycles, ATVs | 1980-2025 |
Frequently Asked Questions
Fits Mikuni TM and VM series carbs (e.g., TM40, VM34, VM38, VM40) on many 2-stroke and 4-stroke bikes/ATVs.
Use plug chop method or wideband O2 sensor; #140 is for richer mid-range, common at sea level or with mods.
Hex head style (F4/042), easier to install/remove than slotted round jets.
No, Mikuni jets have different threading; check your carb model.
Installation Guide
Difficulty
Easy
Est. Time
5 min
Tools Required
- Small flathead screwdriver
- Needle nose pliers
Pro Tips
- Remove carb, unscrew old jet from emulsion tube, note position. Clean with carb cleaner. Test jetting after install with plug reads.
Common Mistakes to Avoid
- Not cleaning carb passages before install
- Installing wrong size jet
Comparison vs Stock/OEM
Direct OEM replacement or upgrade for worn jets; precision machined brass same as factory
Improvements
- Consistent fuel flow
- Corrosion resistant
- Easier tuning with hex head
Considerations
- None; identical to OEM specs
Durability & Warranty
Expected Lifespan
Indefinite with proper cleaning; lasts engine life unless clogged
Warranty
Limited lifetime by Mikuni
Maintenance
Clean during carb service (every 20-50 hours); inspect for wear
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