2008 Polaris ATV Sportsman 300 400 H.O. Service Manual, Page 98Get this manual
FUEL SYSTEM Carburetor Function
Carburetor Component Function System Main Components Main Function Main Affect
Mikuni CV Carb Operation
The constant velocity carburetor incorporates mechanically operated throttle plate and vacuum controlled slide valve (vacuum slide)The venturi crosssectional area in the carburetor bore is increased or decreased automatically by the vacuum slide, which moves according to the amount of negative pressure (less than atmospheric) present in the venturiA diaphragm attached to the top of the vacuum slide is sealed to the slide and to the carburetor body forming two chambersThe chamber above the diaphragm is connected to the venturi area by drilled orifice in the center of the vacuum slideThe chamber below the diaphragm is vented to atmospheric pressure by passage on the air box side of the carburetorA spring, installed in the center of the vacuum slide, dampens the slide movement and assists the return of the slideLow Pressure From Venturi Atmospheric Pressure
Maintains specified fuel Float Inlet Pipe, level in float System Needle and Seat, chamber (Level Control) Float, Float Pin (carburetor float bowl)