An apparatus for limiting the travel of a slave piston in a slave piston cylinder in a compression release engine retarder is disclosed. The apparatus is connected to a hydraulic circuit and comprises an internal passageway in the slave piston head. The internal passageway comprises a vertical bore, a horizontal bore, and an annular channel which together provide a path for bleeding off the pressure on the top of the slave piston when the annular channel and an aperture in the slave piston cylinder are aligned. The bleeding of the hydraulic pressure on top of the slave piston clips the motion of the slave piston at a desired stroke. The apparatus includes a locking adjustable foot on the slave piston stem which provides a means to adjust the lash.