2003 Polaris Scrambler 50-90 Sportsman 90 Predator 90 Service Manual, Page 59Get this manual
FUEL SYSTEMCARBURETION The engine of vehicle is operated under wide range of conditions, from idling with the throttle valve remaining almost closed, to full load or maximum output with the throttle valve fully openedIn order to meet the requirements for the proper mixture ratio under these varying conditions, low speed fuel system, or pilot system, and main fuel system are provided in these type of carburetors
Fuel Supply
Idle Adjustment Screw
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