Improve the performance of stock 40 mm Keihin CV-Carburetors. These kits contain all necessary jets, needles, springs and a detailed instruction that leads you step-by-step through the carb tuning and modification for maximum performance on stock motors as well as on motors with performance cams and exhausts. More power throughout the complete RPM-range and better throttle response. Especially recommended when you switch to a Custom air cleaner.