Carburetor with a rotary throttle valve

Abstract

A rotary throttle valve type carburetor including an air intake passage extending through a carburetor body, a cylindrical valve chamber formed perpendicularly to the air intake passage, a throttle valve inserted into the valve chamber, and a throttle valve lever which rotates to impart rotation and axial movement to the throttle valve to thereby regulate the amount of air and fuel drawn through the carburetor. A plurality of circumferentially extending cam surfaces are formed on a bottom face of the throttle valve symmetrical with respect to the axis of the throttle valve, while tapered bores for receiving balls which are adapted to engage with the cam surfaces are formed in a bottom face of the valve chamber. The sliding engagement between the cam surfaces and balls due to rotation of the throttle valve is adapted to provide a predetermined axial movement of the throttle valve. Desirably, a columnar-shaped fitting jig is inserted into the valve chamber to press-fit the balls into the tapered bores so that the balls are disposed at a common height in the valve chamber.