2003 Polaris Deep Snow Snowmobiles Service Manual, Page 137Get this manual
FUEL SYSTEMCARBURETION Mikuni Carburetor
Mikuni carburetors use starter enricher system rather than chokeIn this type of carburetor, fuel and air for starting the engine are metered with entirely independent jetsThe fuel metered in the starter jet is mixed with air and is broken into tiny particles in the emulsion tubeThe mixture then flows into the plunger area, mixes again with air coming from the air intake port for starting and is delivered to the engine through the fuel discharge nozzle in the optimum airfuel ratioThe starter is opened and closed by means of the starter plungerThe starter type carburetor is constructed to utilize the negative pressure of the inlet pipe, so it is important that the throttle valve is closed when starting the engine