Abstract: This invention relates to a hydraulic motor device comprising a cylinder and a piston reciprocating therein said piston being moved in one direction by means of a spring and in the other direction by means of fluid under pressure supplied against one side of the piston, said cylinder including an inlet for fluid at one end and an outlet for fluid at the other end, and said piston including an overflow aperture from one working side to the other, which aperture is controlled by a stop valve that is either completely open or completely closed depending upon its impact against two spaced apart points on the cylinder end walls.