A gerotor motor has a housing located adjacent a port plate. The housing
has two fluid chambers on opposite sides of a disc valve. The disc valve
is in sealing surface engagement with the port plate to prevent fluid from
moving between the fluid chambers. The valve assembly has forward and
rearward sides and has substantially equal volumes of material removed
therefrom so as to balance the port plate against any torsional forces
imposed on the valve assembly which might otherwise deflect the valve
assembly to interfere with its sealing relationship with the port plate.