The improved versions of the ”HS40” flat slide carburetor. Features include a high-flowing 42 mm or 45 mm bore venturi which results in a significantly increased air flow, making this carburetor ideal for modified, high performance engines. However, the 45 mm version is recommended only for very big engines (98 cui +) or pure race applications. A two-piece throttle slide that rolls on stainless roller bearings and a lighter throttle return spring provide positive and comfortable throttle control. Additional advantages are an adjustable low speed air screw, an enlarged needle valve and float bowl, improved starting, more torque throughout the RPM-range and a fully adjustable accelerator pump. Each kit comes complete with instructions for easy installation.