Abstract: The application discloses a combine machine including an air baffle plate for adjusting air flow to a cleaning chamber used for removing waste material from grain. The cleaning chamber acts to deliver a predetermined supply of air to such grain material to remove chaff and trash material from the grain. In addition to a manual control, the air is controlled automatically by sensing the manifold pressure. The sensed air pressure is supplied to a cylinder which is connected to a link assembly and to a baffle plate which controls the air supply to the cleaning chamber. Under load the baffle plate is automatically moved toward an open position. When the load is decreased the baffle plate is moved toward a closed position to reduce the air supply delivered to the cleaning chamber.