1971-1973 Arctic Cat Snowmobiles Factory Service Manual, Page 78Get this manual
CARBURETION (VVALBRO) through the venturi equals lower air pressureRegulating air flow velocity by utilizing throttle valve will govern the amount of fuel delivered to the enginecheck valve and channelFuel continues to flow through the channel and to the needle valveThe metering lever spring transmits force on the inlet needle valveEngine suction pulls the metering diaphragm upward, transmitting this same suction through the idle discharge port hole, secondary idle holes, and the part throttle feed holesThe diaphragm action depresses the metering lever and unseats the needle valve, allowing fuel to enter the metering diaphragm chamber and pass through the idle take offThe check valve is now forced open, allowing fuel to pass through the main nozzle feeding the part throttle feed holes
Starting Operation (Choke:)
When the engine is cranked with the choke in closed position, the fuel pump diaphragm pulsates, drawing fuel from the snowmobile fuel tank through the fuel inlet, into the surge chamber, and filtered through the carburetor, and filtered through the carburetor screenThe engine crankcase pulsations transmitted through the external impulse fitting or the internal impulse hole, results in the actuation of the fuel pump diaphragm, which implements the pumping action for the fuel pumpA low pressure area is created on the fuel side of the diaphragmThe fuel is drawn from the surge chamber through the