Abstract: A compressed air motor comprises a cylinder with a piston slidable in said cylinder and connected to a compressed air inlet through a slide valve mechanism which alternately admits respective opposite sides of the cylinder with compressed air for driving the piston in the opposite direction, and which also alternately vents the side of the cylinder in which the piston is moving. The construction includes an action rod mounted for movement in a direction parallel to the piston on each side thereof which is contacted by the piston after predetermined movement thereof. A snap-action lever mechanism is connected between the action rod and the slide valve mechanism so that the action rod, through the snap-action lever mechanism reverses the slide valve during each motion of the piston. The action rod member is returned to its starting position during the return movement of the piston by means of a stop member connected to an extension of the piston.