Mikuni Hsr42 Smooth Bore Carburetor For Harley Big Twin The Mikuni HSR carburetor is a go-to choice for performance-minded Harley riders who want immediate throttle response and tunable control. Designed for custom applications and high-performance engines, it delivers smooth, consistent fueling under hard use. Its long-standing reputation is built on durability and results. Features: For the high-performance engine builder who needs a carb for specific custom applications HSR smoothbore carburetors offer excellent throttle response and control Well made for years of dependable service Made in Japan