When a pressure plate of a clutch for motorcycles and the like is moved to engage and disengage driving friction plates and driven friction plates, a rod driver connected to an operation rod is constructed such that a pair of operation members is assembled so as to face a plurality of guide grooves formed on a surface of interposing balls, wherein the plurality of guide grooves is formed along an imaginary circle having a radius of about 19.3 mm on the faces of each of the operation members, and the balls have a diameter of about 9.5 mm. One of the operation members is rotated with respect to the other operation member to separate the operation members because bottom surfaces of the guide grooves are slanted by an angle of between 13.7° through 14.4° from the faces, and centers of the guide grooves are most deep, as much as about 3.872 mm, in the guide grooves, whereby the clutch is securely disengaged in use by a small force.