Mikuni HSR42 Easy Carburetor Kit For Harley Big Twin 1990-2006

The Ultimate Smoothbore Power: Mikuni HSR42 Easy Kit for Harley Big Twins

For riders of 1990–2006 Harley-Davidson Big Twins, the factory constant-velocity (CV) carburetor is often the primary obstacle to true performance. The Mikuni HSR42 Easy Carburetor Kit is widely considered the single best performance modification for the Evolution 1340 and Twin Cam 88 engines. Unlike the vacuum-operated stock units, the HSR42 is a mechanical smoothbore carburetor. It features a flat slide that rides on stainless steel roller bearings, providing a straight path for air and fuel to enter the engine. This eliminates the turbulence and lag associated with stock carburetors, resulting in a motorcycle that feels instantly more responsive, more powerful, and significantly more refined.

The “Easy Kit” Advantage: Performance Without the Complexity

The Mikuni “Easy Kit” (Part Number 42-18) was created for the rider who wants racing-level performance without a complicated installation process. What sets this kit apart is its ability to interface perfectly with your original equipment. It is designed to fit onto your stock Harley-Davidson intake manifold and utilizes your original factory throttle cables. Additionally, the kit includes a specialized adapter that allows you to reuse your stock air cleaner cover, maintaining the classic look of your bike while hiding a high-performance secret underneath. By eliminating the need for new manifolds and custom cables, the HSR42 Easy Kit offers the highest “horsepower-per-dollar” value in the V-Twin aftermarket.

Precision Engineering and Instant Response

The hallmark of the Mikuni HSR42 is its roller-bearing throttle slide. While other performance carburetors can feel heavy or stiff at the grip, the Mikuni slide glides effortlessly, even under high engine vacuum. This provides a precise, “one-to-one” connection between your right hand and the rear tire.

• Adjustable Accelerator Pump: The HSR42 features a fully tunable accelerator pump, allowing you to dial in the exact amount of fuel needed to eliminate flat spots and off-idle hesitation.
• Superior Fuel Atomization: The advanced needle and jet design ensures that fuel is broken down into a finer mist than stock carburetors, leading to more efficient combustion and smoother power delivery.
• Increased Airflow: The 42mm venturi is perfectly sized for 80″, 88″, and 95″ engines, providing a significant boost in mid-range torque and top-end horsepower.

Technical Fitment and Model Coverage

This kit is specifically tailored for the transition years between the Evolution and Twin Cam eras, covering nearly two decades of Harley-Davidson history.

• Compatible Models: Fits 1990–1999 Evolution Big Twins and 1999–2006 Twin Cam models (Carbureted).
• Included Hardware: The kit comes with the HSR 42mm carburetor, air cleaner backing plate adapter, and easy-to-follow instructions.
• Tuning Versatility: Because of its immense popularity, the HSR42 has a massive ecosystem of jets and needles available for riders at high altitudes or those with high-compression engine builds.
• Long-Term Reliability: Built with high-grade components that are resistant to the heat and vibration of air-cooled V-Twin engines.

Why Choose Mikuni for Your Big Twin?

Choosing the Mikuni HSR42 Easy Kit is an investment in the ride quality of your Harley-Davidson. It transforms the “lazy” feel of a stock carbureted Big Twin into a crisp, aggressive machine that is a joy to ride in both city traffic and on the open highway. You will experience easier cold starts, a more consistent idle, and a level of acceleration that will make your bike feel years younger. Backed by Mikuni’s decades of racing dominance, the HSR42 is the gold standard of V-Twin fuel delivery. Don’t settle for “good enough” from your factory carb—experience the smoothbore difference today.

Note: For 2004–2006 models, check your specific manifold clearance if using an aftermarket air cleaner. Professional tuning is recommended to ensure the air-fuel ratio is optimized for your exhaust system.