1971-1973 Arctic Cat Snowmobiles Factory Service Manual, Page 81Get this manual
CARBURETION (VVALBRO) Full Throttle Operation (Wide Open)
As the throttle valve opens progressively further from part throttle operation, the air velocity through the venturi increasesAt full throttle operation, fuel passes around the power needle and is discharged through the main nozzle into the venturiWhen full throttle is obtained, air is mixed with fuel in the main nozzle through the nozzle air bleedSuction (vacuum) created by the reciprocating action of the engine piston draws fuel and air as the ports are exposed by the throttle valve position
FULL THROTTLE OPERATION
Venturi Choke valve
Nozzle air bleed Channel Needle valve Channel Metering diaphragm chamber Secondary fuel pump Check valve Chamber Outlet valve Channel
Throttle
valve open
Main nozzle Part throttle holes Secondary idIe ho les Idle discharge port