2008 Polaris ATV Predator 50, Sportsman Outlaw 90 Service Manual, Page 92Get this manual
FUEL SYSTEM Float System
The float system is designed to maintain constant height of gasoline during operationWhen the fuel flowing from the fuel pump into the float chamber through the needle valve reaches the constant fuel level, the floats riseWhen the buoyancy of the float and the fuel pressure of the fuel pump balance, the needle valve seals the orifice in the needle seat, preventing further fuel delivery, and the level of fuel in the bowl remains relatively constantThe fuel level in the bowl assists in controlling the amount of fuel in the fuel mixtureToo high level allows more fuel than necessary to leave the nozzle, enriching the mixtureToo low level results in leaner mixture, since not enough fuel leaves the nozzleTherefore, the predetermined fuel level should not be changed arbitrarily
Pilot Mixture Screw
The pilot mixture screw controls the fuel mixture from idle to low speedsThe tapered tip of the mixture screw projects into the fuel mixture passage leading to the pilot jet air bleedsBy turning the screw in or out, the cross sectional area of the air passage is varied, in turn varying the pilot jet air supply and changing the mixture ratio