Secondary High Speed Circuit

Secondary throttle valve is constructed so as to react to vacuum in the venturi. Vacuum jets are provided in the venturi sections of primary and secondary stages. Average vacuum of both jets acts in the diaphragm chamber and moves the diaphragm. Diaphragm and secondary throttle valve are connected by a link to open the throttle valve according to vacuum. Secondary throttle valve cannot be opened until primary throttle valve is opened to 50°. This is controlled by the lock-off lever installed on the primary shaft and the stop on the secondary shaft. When primary throttle opens more than 50°; secondary throttle is released from locked position and opens in proportion to vacuum. Then fuel from main jet is mixed with air from main air bleed and sprayed from main nozzle into the venturi.