1999 Polaris SLH, SLTH, SLX, SLTX, PRO785 Factory Service Manual, Page 94Get this manual

1999 Polaris SLH, SLTH, SLX, SLTX, PRO785 Factory Service Manual, Page 94

FUEL SYSTEMCARBURETION System OperationKeihin Carburetor The Keihin CDK II carburetor is floatless diaphragm typeSeveral
applying pressure on the control arm in the fuel chamberThis reduces pressure on the inlet needle and allows it to lift more
easily off the seatWhen the engine is running, pressure in the carburetor venturi (and therefore the fuel chamber) is less
than atmosphericThis increases the effect of the atmospheric pressure on the diaphragm and lever and overcomes spring pressureWhen
the lever return spring pressure is overcome by these forces, the needle lifts off of the seat or "pops off", allowing pressurized
fuel from the fuel pump to enter the fuel chamberFuel inlet needle "pop off" pressure is influenced by many factorsAtmospheric
pressure, venturi low pressure, the amount of spring pressure on the control arm, and fuel pressure from the fuel pump all
have an affect on operating pop off pressureAll of these forces combined regulate the amount of fuel that enters the carburetor