A rotary vane air or gas motor is provided with a primary exhaust port having an exhaust fluid throttling valve therein for controlling motor speed. The motor includes a secondary exhaust port for discharging exhaust fluid flow from the motor expansible chambers after cutoff of the primary exhaust port. A flow sensing vane member is movably disposed in a flow passage in communication with the secondary exhaust port and is responsive to flow variations to actuate the exhaust fluid throttling valve by connecting linkage. The interconnected exhaust fluid throttling valve and flow sensing vane function as a motor speed limiting governor.