The Mikuni HSR42 Performance Carburetor Kits are designed for Sportsers, Buells and stock Big Twins and offer a 25 percent increase in power and torque when used with an aftermarket exhaust system. All Mikuni HSR smoothbore carburetors offer the highest air flow possible while providing highly accurate fuel metering, more power, and precision throttle response. Carburetors are designed with an 8-roller bearing flat throttle slide assembly for smooth throttle control with reduced effort.