PURPOSE: To make it possible to maintain a pedalling range of a pedal lever constant and to improve safety upon cutting of a torque transmitting coil spring by having a coupling arm coaxially mounted onto the shaft of the pedal lever so that the coupling arm follows wear of a clutch facing.

CONSTITUTION: A pedal lever 3 is returned to the operator side by a spring 7 in the released state of the pedal lever 3 and a release lever 13 is rotated in the direction indicated by a arrow. Therefore, a threaded lever 15 attached to the lower section of the release lever 13 urges the free end of a torque transmitting coil spring 10 in the direction of unwinding thereof for spreading out a sleeve 11 so that a gear 9 is free from the spring 10, in which a correction is automatically made, corresponding to a wear of a clutch facing, since a coupling arm 6 takes a position corresponding to the returned position of the clutch and is in the rotatable state thereof. Then, a lock gear 16 is meshed with a gear 5 simultaneously with the frictional coupling between the gear 9 and the spring 10 when the clutch lever 3 is pedalled, thereby the gear 9 is locked against rotation.