PURPOSE: To eliminate frictional resistance to smooth the rotation of a choke shaft by fitting-installing a cylindrical bush on the outer peripheral surface of the choke shaft coaxially with the choke shaft so that a clearance is kept between the inner peripheral surface of the bush and the outer peripheral surface of the choke shaft.

CONSTITUTION: A choke valve 8 is fixed to the part equivalent to the air feed cylinder part of a choke shaft 6 penetrating and extending through a carbureter body 7, and a relief lever 9 is fixed to the tip of the choke shaft 6 by caulking. Besides, a cylindrical-bush 10, the inside diameter of which is formed larger than the outside diameter of the choke shaft 6, is fitted into a boss 7b projectingly formed outside the part of the carbureter body 7 penetrated by the choke shaft 6, and supported as a cantilevered part. The choke shaft 6 is inserted into the bush 10 so as to keep a clearance D between them. Further, a choke wire lever 12 and a choke breaker lever 14 are rotatably supported on both sides of a flange part 10a formed on the bush 10.