opening 41 in the cover plate mounting the sleeve bearing 43 therein relieves the pressure in the opening for the output shaft 32 to provide relief and protection of the main seal 45 and for the circulating of the hydraulic fluid that act as a lubricating oil for the shaft and bearings in fig3 a a modification to the motor primarily involving changes to the pressure plate is disclosed in this modification the pressure plate 62 u2032 is provided with spring biased check valves 112 in the radially inner passages 83 u2032 leading to the high pressure rotor drive chamber this check valve construction opens from the force of a predetermined pressure acting on the ball valve element of the check valve for effecting the build up of high pressure in the pressure balancing chambers for improved rotor balancing also the increased undervane pressure optimizes u201c pop out u201d of the vanes 46 to operatively engage the cam before the high pressure drive chamber 78 is fully charged in any event with this invention the motor vanes will be quickly u201c popped out u201d in response to the delivery of the high pressure from the pump 14 at a high point on the pressure gradient curve with such response the employment of spring devices such as vane springs 116 and their threaded rotor attachment fasteners 117 of fig6 effecting the engagement of the vanes 11 8 with the cam 120 is not required moreover with the present invention the force applied to each of the vanes is equal so that vane wear is equal for enhanced vane cam ring sealing and increased service life.