PISTON THROTTLE VALVE TYPE CARBURETOR

摘要

PROBLEM TO BE SOLVED: To suppress a rise of a piston throttle valve by releasing an intake vacuum acting on a fuel storage tank from an intake passage just after a cold engine start-up. SOLUTION: The cupped piston throttle valve 18 is vertically movably supported at right angles to the intake passage 13 crossing through a carburetor body 6. An atmospheric chamber 10 is defined under a diaphragm 3 coupled to the upper end of the piston throttle valve 18, and a vacuum chamber 5 is defined over the diaphragm 3 so as to house a return spring 4 and introduce thereinto an intake vacuum under the piston throttle valve 18. The fuel storage tank 24 is coupled to the bottom wall of the carburetor body. A fuel control needle valve 20 supported on the lower end of the piston throttle valve 18 is passed through a main fuel supply pipe 28 extending from the intake passage 13 to the fuel storage tank 24. A passage extending from the bottom of the fuel storage tank 24 is connected to a variable venturi part of the intake passage 13 via an on-off valve 41 openable by an idle operation.