The motocross world knows PWK. The Keihin PWK carburetor is the dominant carburetor on the factory motocross machines. Because of their great performance they come stock on a lot of the leading brand bikes. With these features you can take advantage of Keihin's superior performance. PWK features: Chromed semi-flat (D) throttle valve for excellent response and more flow at high rpm. Throttle bores sized to give maximum power. Easy jetting with Jetting parts available. Available in six popular sizes to cover all your horsepower requirements.