To properly adjust a fuel control tool by rapidly responding to sudden fluctuation in engine speed and to prevent generation of engine stall and overrunning that could be caused by sudden load fluctuation, or the like.

A threaded part 12 which rotates in conjunction with a governor weight 10 and which has a spiral thread around the axis 11 of a governor shaft 8 is provided along the governor shaft 8. A projecting/retreating piece 13 is fitted around the threaded part 12 and spirally moved out by a governor force F and the spring force S of a governor spring 5. The spiral direction of the thread of the threaded part 12 is set so that when the rotating speed of the threaded part 12 is higher than that of the piece 13, the piece 13 is advanced spirally, and so that when the rotating speed of the screw part 12 is lower than that of the plunger 13 piece 13 is apirally moved back.