MIKUNI FBN46-42-8002 High Performance Carburetor 46MM

( Brand: Mikuni ), ( Manufacturer Part Number: FBN46-42-8002 ), ( Part Type: Carburetor ), ( Bore Size: 46mm )

Review MIKUNI Super Bn 46mm High Performance Carburetor Bn46-42-8002

The **Mikuni FBN46-42-8002 46mm High-Performance Carburetor** is a precision-engineered fuel delivery system designed to elevate the performance of high-revving, air-cooled engines, particularly those found in classic and modern sport bikes, dirt bikes, and off-road applications. Built upon Mikuni s legendary reputation for reliability and cutting-edge carburetor technology, this **BN46-42-8002** model combines a **46mm bore** with a **high-performance float bowl (FBN series)** to deliver an optimal blend of throttle response, fuel efficiency, and power output across a wide RPM range. The **8002** designation indicates a meticulously tuned **needle and jet combination**, fine-tuned for engines requiring a balance of low-end torque and high-end horsepower, making it an ideal choice for both street and track applications where smooth acceleration and peak performance are critical.

At its core, the **FBN46-42-8002** features Mikuni s **floating bowl needle system**, which ensures consistent fuel delivery by maintaining a stable fuel level regardless of engine angle or acceleration. This design minimizes fuel starvation during aggressive throttle inputs, a common issue in high-performance setups, while the **precision-machined bore** and **high-quality rubber gaskets** contribute to a leak-free seal that enhances durability. The **needle jet (42)** and **pilot jet (8002)** are carefully calibrated to optimize fuel-air mixture ratios, allowing for finer adjustments to suit specific engine modifications, such as increased compression, forced induction, or exhaust tuning. Whether paired with a stock engine or a heavily modified powerplant, this carburetor excels in delivering **linear power delivery**, reducing hesitation, and maximizing efficiency without sacrificing drivability.

Constructed from **high-grade aluminum** for strength and corrosion resistance, the **FBN46-42-8002** incorporates Mikuni s **patented slide mechanism**, which features a **smooth, low-friction action** to ensure crisp throttle response and minimal lag. The **dual-choke design** further enhances airflow efficiency, allowing for better vacuum control and improved engine breathing, particularly under heavy loads. For ease of maintenance, the carburetor is equipped with **quick-disconnect fuel lines** and a **removable float bowl**, making routine cleaning, jet adjustments, and needle replacements straightforward. Additionally, Mikuni s **universal mounting compatibility** ensures that the FBN46-42-8002 can be seamlessly integrated into a variety of engine setups, from stock applications to custom builds, with minimal modifications required.

Beyond its technical specifications, the **Mikuni FBN46-42-8002** is a testament to the brand s commitment to performance and craftsmanship. Its **durable construction**, **precise engineering**, and **adjustable nature** make it a versatile choice for riders seeking to push their engines to their limits while maintaining reliability. Whether used in a **classic Honda CB750**, a **modified dirt bike**, or a **high-revving sportbike**, this carburetor stands out as a **high-performance workhorse** that balances power, control, and longevity. For enthusiasts who demand nothing less than excellence in fuel delivery, the **FBN46-42-8002** is an indispensable component for achieving peak engine performance with confidence.

The Mikuni FBN46-42-8002 is a high-performance carburetor designed for small engines, particularly those in go-karts, dirt bikes, and other high-revving applications. Below is a detailed breakdown of its pros and cons, followed by a conclusion and recommendation.

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### **Pros of the Mikuni FBN46-42-8002**

1. **High Performance and Power Output**

The FBN series is engineered for high-revving applications, delivering improved throttle response, better fuel efficiency at high RPMs, and increased horsepower compared to stock carbs. It features a larger bore (46mm) and optimized airflow, making it ideal for engines that require more power without excessive fuel consumption.

2. **Precision Engineering and Durability**

Mikuni is a well-regarded brand known for its quality manufacturing. The FBN46-42-8002 is built with durable materials, including a forged aluminum body and precision-machined internals. This ensures longevity, especially in demanding applications like go-karts or racing engines.

3. **Adjustability and Tuning Flexibility**

The carburetor includes an adjustable idle mixture screw, throttle stop screw, and often a pilot jet or main jet that can be modified for fine-tuning. This allows racers and tuners to optimize performance for specific engine setups, fuel types, and track conditions.

4. **Compatibility with High-Octane Fuels**

The FBN series is designed to work well with high-octane fuels (e.g., methanol, nitromethane, or premium gasoline blends), which are common in racing applications. This reduces the risk of detonation and allows engines to run at higher RPMs safely.

5. **Reduced Fuel Consumption at High RPMs**

Unlike some stock carbs that flood or struggle at high speeds, the FBN46-42-8002 is optimized for efficient fuel delivery at elevated RPMs. This is particularly useful in go-karts and dirt bikes where sustained high-speed performance is critical.

6. **Aftermarket Support and Availability**

Mikuni has a strong aftermarket presence, with widespread availability of replacement parts, gaskets, and tuning guides. This makes maintenance and upgrades easier compared to some lesser-known brands.

7. **Smooth Throttle Response**

The design of the FBN series minimizes hesitation and provides a linear power delivery, which is beneficial for racing applications where quick acceleration is essential.

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### **Cons of the Mikuni FBN46-42-8002**

1. **Higher Initial Cost**

Compared to stock carbs or budget aftermarket options, the FBN46-42-8002 is more expensive. This can be a significant investment, especially for hobbyists or those on a tight budget.

2. **Requires Professional Installation and Tuning**

While the carburetor itself is robust, improper installation (e.g., incorrect gasket placement, misaligned throttle linkage, or wrong jet sizes) can lead to poor performance or engine damage. Tuning may require adjustments to the engine s ignition timing, fuel mixture, and air intake, which can be complex for beginners.

3. **Fuel and Air Filter Maintenance**

The FBN46-42-8002 benefits from clean air and fuel, so neglecting air filters or using contaminated fuel can clog the jets and reduce performance. This adds to the ongoing maintenance requirements.

4. **Potential for Overfueling or Lean Conditions**

If not properly tuned, the carburetor can either flood the engine (too much fuel) or run lean (too little fuel), leading to rough idling, stalling, or reduced power. This requires careful calibration, especially when switching between different fuel types.

5. **Limited Compatibility with Stock Engines**

The FBN46-42-8002 is not a drop-in replacement for all engines. It may require modifications to the intake manifold, throttle linkage, or even the engine s compression ratio to perform optimally. Consulting with an engine specialist is advisable before installation.

6. **Wear and Tear on Engine Components**

High-performance carbs like the FBN46-42-8002 push engines to their limits, which can accelerate wear on components such as pistons, rings, and bearings if the engine is not properly maintained or upgraded to handle the increased stress.

7. **Learning Curve for Tuning**

Achieving the best performance often involves experimenting with jet sizes, idle mixture, and other adjustments. This can be frustrating for those without prior experience in carburetor tuning or engine management.

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### **Conclusion**

The Mikuni FBN46-42-8002 is a high-quality, high-performance carburetor that excels in applications requiring significant power and reliability, such as go-karts, dirt bikes, and racing engines. Its precision engineering, adjustability, and compatibility with high-octane fuels make it a strong choice for serious racers or enthusiasts willing to invest in performance. However, its higher cost, complexity of installation and tuning, and the need for meticulous maintenance may not suit beginners or those on a tight budget. Additionally, it is not a universal upgrade and may require engine modifications or professional tuning to unlock its full potential.

For those who prioritize power, durability, and tunability, the FBN46-42-8002 is an excellent investment. For casual users or those new to high-performance tuning, a more affordable or simpler carburetor might be a better starting point.

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### **Recommendation**

- You are running a high-revving engine (e.g., go-kart, dirt bike, or racing engine) and need a significant power boost.

- You are willing to invest in professional installation and tuning to ensure optimal performance.

- You have experience with carburetor tuning or are prepared to learn, as improper setup can lead to poor results.

- Your budget allows for the higher upfront cost, and you expect long-term benefits in performance and reliability.

- You are on a tight budget and can achieve similar gains with a more affordable carburetor (e.g., Walbro, Keihin, or a slightly smaller Mikuni model).

- You lack experience with carburetor tuning and are not willing to invest time in learning or hiring a professional.

- Your engine is not compatible with the FBN series without significant modifications, and you prefer a simpler upgrade.

For best results, pair the FBN46-42-8002 with high-quality fuel, air filters, and regular maintenance. If possible, consult with a racing engine specialist or tuner to ensure the carburetor is properly matched to your engine s specifications.

Details:

Slip on mufflers in applications whereby the catalyst is not contained original muffler an example of a replacement part. Vito-tip needle valve helps provide consistent pop-off control. These parts do not require approval as long they are used on public highways. Check the shipping calculator for estimated costs.

Ask a question at the bottom of. Replacement Parts that have the same function and affect on emissions as they are replacing. This means that if a vehicle was not originally equipped with catalyst and all other emissions related controls were connected such as oxygen sensors are reconnected, then the part is considered Replacement Part. High performance Super BN design with extended throttle shaft.

EO number and will arrive with appropriate labels to indicate the approved status. Competition or Racing Vehicle Parts that are used exclusively in competition on race only vehicles. It must be a competition vehicle and not used at any time on public highway.

Full exhaust systems installed on vehicles that did not originally contain a catalyst and whereby the design allows re installation original function of any other emissions control related components are also considered replacement parts. Labeling a product as being for Racing Only or Closed Course Competition is not sufficient it to be included under this classification. Some items are made to order and can have longer lead times; check the shipping details for an estimate. Modified Parts that alter the emissions control related performance from original part they are replacing, These may have catalysts in them but perform differently equipment or require alteration elimination of other components such as oxygen sensors.

Silver finish. If the vehicle has a catalyst and installation of part does not remove catalyst, all other emissions related controls are reconnected, then this is considered replacement. Primer-type cold start system no butterfly choke to help increase airflow.

part #: fbn46428002 prices

• $165.00-$175.50

specifications jetskiintakeez:

• brand: Mikuni
• mpn: Fbn46-42-8002
• part type: Carburetor
• bore size: 46mm

offer jetskiintakeez:

• quantity: 8
• started: March 3, 2026
• options: Ship-to-home
• sold: 0
• availability: In Stock

general jetskiintakeez:

• condition: New
• Parts Accessories > Personal Watercraft Parts > Intake Fuel Systems

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• type: Fixed
• class: Standard
• cost: $0.00
• service: Standard
• transit: 3-7 Days

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• # reviews: 110243
• city: Lebec, California
• rating: 99.8%

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• policy: Returns Accepted
• time: 30 Days
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