1985-1995 Polaris ATV and Light Utility Hauler Service Manual, Page 351Get this manual
ENGINESCARBU RETION
Magnum CV Carb Operation
The constant velocity carburetor used on the Magnum provides number of useful benefitsAmong these are smooth acceleration, good throttle response, optimum fuel atomization and good fuel economyThe carburetor incorporates mechanically operated throttle plate and vacuum controlled slide valve (vacuum slide)The venturi cross-sectional 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 slideWhen the throttle plate is opened and engine speed begins to increase, the pressure in the venturi (and therefore in the chamber above the diaphragm) becomes significantly lower than atmosphericAtmospheric pressure in the chamber below the diaphragm forces the diaphragm upward, raising the slide against spring pressureWhen the pressure above and below the diaphragm are nearly equal, the slide moves downward under spring pressureRaising or lowering the slide increases or decreases the cross sectional area in the venturi, and therefore the air velocity in the venturi is kept relatively constantThis provides improved fuel atomization and optimum fuelair ratio