To prevent hunting of a governor lever not only within an idling revolution area but also in a wide range and prevent fall-off of an idle spring.

A governor weight and a start spring 8 are interlocked and connected with a rack pin 2a of a fuel injection pump 1 via a governor lever 3, an idle spring 10 is faced so as to be abutted on the end face 4 on the fuel reduction side of the governor lever 3, the governor lever 3 and a speed control lever are connected via a governor spring, and tension of the governor spring is constituted to be adjusted and operated by the speed control lever. The idle spring 10 is constituted of a nonlinear conical coil spring and the tapered base end winding and fixing part 10a is wound and fixed on a part 16 to be wound and fixed of an idle adjusting tool 15.