PURPOSE: To simplify the operation of an accelerator lever by setting the length of a linking mechanism for a main clutch and a linking mechanism for an accelerator lever respectively so that an engine start position which is at a little higher speed than the idling position of an engine 1 may exist.

CONSTITUTION: A structure for setting an engine 1 at a full rotation condition from an idling condition by ON/OFF-switching a main clutch 5, and to an engine start position and a light load rotation working position within a clutch OFF operating range is constituted by setting the length of the linking mechanism 6 of the main clutch 5 and the linking mechanism 10 of an accelerator lever 9a. The length of the linking mechanism 10 of the accelerator lever 9a is set for the linking mechanism 6 of the main clutch 5 so that the accelerator lever 9a may be operated to A-D positions by ON/OFF switching the main clutch 5.