Abstract: An air turbine starter includes a starter housing and a check valve. The check valve is disposed within the starter housing and is configured, in response to a pressure differential across the check valve, to selectively allow and prevent lubricant to flow therefrom. The check valve includes a valve includes a valve body, a valve seat, a valve bore, a valve element, and a plurality of rounded grooves. The valve bore is formed in the valve body between the valve seat and the lubricant outlet port. The valve element is disposed within the valve bore and is movable between a plurality of open positions and a closed position. The rounded grooves are formed in the valve body, and are disposed adjacent to, and in fluid communication with, the valve bore to improve lubricant to flow past the valve element when the valve element is in an open position.