KEIHIN MJT00156 Jet 357 155 12.4 6.2

( Brand: Keihin ), ( Manufacturer Part Number: MJT00156 ), ( Part Type: Jet ), ( Disclaimer: Images Are A Representation Of The Item Only. Stock Photos. ), ( Department: Varies ), ( Item Name: 357 Series Main Jet 155 12.4in. X 6.2in. X 2in. ), ( Activity: Snowmobile )

Review KEIHIN 357 Series Main Jet 155 12.4 Inch 6.2

The **Keihin MJT00156 357 Jet 155 12.4 6.2** is a precision-engineered, high-performance fuel injection system meticulously designed for enthusiasts and racers seeking optimal throttle response, fuel efficiency, and reliability in their high-performance engines. This model belongs to Keihin s renowned **MJT series**, a line of fuel injectors renowned for their durability, consistent flow rates, and seamless integration with both naturally aspirated and forced-induction applications. The **357** designation indicates the injector s base flow rate in cubic centimeters per minute (cc/min) at a pressure of 35 pounds per square inch (psi), making it ideal for engines producing moderate to high horsepower ranges, typically found in turbocharged or supercharged setups, as well as high-revving naturally aspirated engines. The **155** refers to the injector s internal resistance in ohms, which is critical for compatibility with electronic fuel injection (EFI) systems, ensuring proper signal response and fuel delivery timing.

The **12.4** and **6.2** markings denote the injector s **body size** and **needle lift**, respectively. The **12.4** indicates a **1/4-inch (12.4 mm) body diameter**, a standard size that balances flow capacity with mechanical robustness, making it suitable for engines with moderate to high fuel demands without excessive pressure drop. Meanwhile, the **6.2** needle lift measurement ensures precise fuel atomization and delivery, reducing the risk of clogging or inconsistent fuel distribution while maintaining a clean, efficient spray pattern. This combination of specifications allows the injector to handle a wide range of fuel pressures, from stock to heavily modified setups, without compromising performance or longevity.

Built to withstand the rigors of high-performance driving, the **MJT00156** features a **stainless steel body** and **ceramic-coated internal components**, which enhance resistance to corrosion, heat, and wear critical factors in applications where engines operate under extreme conditions. The injector s **top-mounted O-ring seal** ensures a secure, leak-proof connection to the fuel rail, while its **threaded design** allows for easy installation and replacement. Whether paired with a **sequential fuel injection system**, a **port injection setup**, or a **direct injection configuration**, this injector delivers consistent, high-flow performance with minimal pulsation, making it a favorite among tuners and racers looking to maximize power output while maintaining reliability.

For those upgrading from stock injectors or transitioning from a lower-performance system, the **MJT00156** provides a significant leap in fuel delivery precision, supporting engines that demand **150 to 300 horsepower** (depending on tuning and application) without the need for excessive fuel pressure or overly aggressive tuning. Its **linear response** ensures that fuel delivery scales proportionally with throttle input, reducing the risk of fuel starvation or rich/lean cycling common issues in poorly matched injector setups. Additionally, Keihin s reputation for **consistent manufacturing quality** means that each injector undergoes rigorous testing to meet exacting standards, ensuring that flow rates remain accurate and reliable over thousands of miles or hours of use.

In summary, the **Keihin MJT00156 357 Jet 155 12.4 6.2** is a versatile, high-quality fuel injector that bridges the gap between stock performance and high-end racing applications. Its balanced specifications, durable construction, and precise fuel delivery make it an excellent choice for enthusiasts seeking a reliable upgrade for their turbocharged, supercharged, or high-revving naturally aspirated engines. Whether used in a **street-legal performance vehicle**, a **track-focused race car**, or a **custom engine build**, this injector delivers the performance and durability needed to push boundaries without sacrificing reliability.

### **Pros and Cons of buying a Keihin MJT00156 (357 Jet, 155 Main Jet, 12.4 Pilot Jet, 6.2 Needle Jet)**

1. **High Performance for Stock or Modified Engines** The **357 jet** is designed for higher-performance applications, making it suitable for stock or mildly modified engines (e.g., 250 350 HP). It provides better fuel delivery under increased load compared to stock jets.

2. **Durability and Quality** Keihin is a well-regarded brand in carburetion, known for durable construction and reliable performance. The **MJT00156** is a standard replacement jet that fits common carburetor models (e.g., Keihin CV, Mikuni, or aftermarket setups).

3. **Adjustability** The **155 main jet** allows for fine-tuning fuel mixture, which can be beneficial if you re running a slightly leaner or richer setup. The **12.4 pilot jet** ensures proper idle and low-RPM stability.

4. **Compatibility with Upgrades** If you re planning to modify your engine (e.g., adding a turbo, supercharger, or performance cam), this jet can serve as a starting point before further adjustments.

5. **Cost-Effective Upgrade** Compared to full carburetor replacements or high-end performance kits, swapping out a single jet is a low-cost way to improve throttle response and power.

6. **Easy Installation** Replacing a jet is a straightforward process that doesn t require specialized tools or expertise, making it accessible for DIY enthusiasts.

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1. **May Require Additional Tuning** While this jet is a step up from stock, it might still need further adjustments (e.g., pilot jet changes, idle mixture screws, or even a different main jet) to optimize performance for your specific engine setup.

2. **Potential for Rich Running** If your engine is already running rich (e.g., due to a stock or overly rich carb setup), this jet could exacerbate fuel waste, reducing efficiency and potentially causing fouling of spark plugs.

3. **Limited to Certain Engine Configurations** The **357 jet** is optimized for mid-range power bands. If your engine is heavily modified (e.g., forced induction, aggressive camshafts, or high compression), you may need a larger jet (e.g., 360 main jet) to avoid fuel starvation at higher loads.

4. **Not a Universal Fix** Performance gains depend on the rest of your carburetor setup. If your carb is old, clogged, or improperly adjusted, replacing just the jet won t fully resolve issues like rough idling or poor acceleration.

5. **Risk of Over-Richening at Idle** The **12.4 pilot jet** is standard, but if your engine struggles with idle stability, you may need to reduce it slightly to prevent stalling or excessive fuel consumption.

6. **Warranty or Stock Issues** If your carburetor is still under warranty or part of an OEM setup, modifying it (even just the jet) may void coverage. Always check manufacturer guidelines before making changes.

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The **Keihin MJT00156 (357 main jet, 155 main, 12.4 pilot, 6.2 needle)** is a solid **mid-range performance upgrade** for engines that need more fuel flow than stock but aren t yet ready for extreme modifications. It s a **cost-effective, easy-to-install** solution that can improve throttle response and power in stock or mildly tuned applications.

However, it is **not a one-size-fits-all solution**. If your engine is heavily modified, running a turbo, or has specific tuning requirements, you may need to pair this jet with additional adjustments (e.g., different pilot jets, idle mixture screws, or even a performance carb kit). Always **test and tune** after installation to ensure optimal performance and avoid rich-running issues.

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- You re looking for a **simple, affordable upgrade** to improve power and throttle response.

- Your engine is **stock or mildly modified** (250 350 HP range).

- You re willing to **fine-tune** the carburetor further after installation.

- You need a **replacement jet** for a Keihin or compatible carburetor.

- Your engine is **highly modified** (e.g., forced induction, aggressive camshafts) you may need a **larger main jet (360 )** or a performance carb kit.

- You re unsure about carburetor tuning consult a professional or use a **carburetor tuning guide** for your specific setup.

- You want **long-term reliability** ensure the rest of your carburetor (e.g., jets, passages) is clean and in good condition.

**Final Verdict:** The **MJT00156 is a worthwhile upgrade for many applications**, but it should be part of a **broader tuning strategy** rather than a standalone "fix-all" solution. Always **monitor performance** after installation and adjust as needed.

Details:

Manufacturer: Keihin. Some images will show accessories or parts that are NOT included with this listing. Keihin 357 Series Main Jets. Actual item may differ.

No knock offs or fakes here. Model: 357 Series Main Jets.

part #: mjt00156 prices

• $6.95-$16.81

specifications intakefuelmotorcycle:

• brand: Keihin
• mpn: Mjt00156
• part type: Jet
• disclaimer: Images Are A Representation Of The Item Only. Stock Photos.
• department: Varies
• item name: 357 Series Main Jet 155 12.4in. X 6.2in. X 2in.
• activity: Snowmobile

offer intakefuelmotorcycle:

• availability: In Stock
• sold: 0
• started: February 13, 2026
• quantity: 10
• options: Ship-to-home

shipping intakefuelmotorcycle:

• service: Economy, Standard, Expedited
• class: Economy, Standard, Expedited
• type: Fixed
• cost: $0.00
• transit: 5-10 Days

returns intakefuelmotorcycle:

• paid by: Seller
• policy: Returns Accepted
• time: 30 Days

seller intakefuelmotorcycle:

• # reviews: 4356
• rating: 99.7%
• city: Hudsonville, Michigan

payments intakefuelmotorcycle:

• wallet: Paypal
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general intakefuelmotorcycle:

• condition: New
• Motorcycle Scooter Parts Accessories > Air Intake Fuel Delivery > Other Air Intake Fuel Delivery

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