2008 Polaris Sportsman 500 EFI/X2/Touring/500 H.O. Service Manual, Page 149Get this manual
CARBURETORSPORTSMAN 500 Main System
As throttle valve (1) is opened, engine speed rises, and this increases negative pressure in the venturiConsequently the vacuum slide (2) moves upwardThe fuel in float chamber (3) is metered by main jet (4), and the metered fuel enters needle jet (5), in which it mixes with the air admitted through main air jet (6) to form an emulsionThe emulsified fuel then passes through the clearance between needle jet (5) and jet needle (7), and is discharged into the venturi (A)Mixture proportioning is accomplished in needle jet (5); the clearance through which the emulsified fuel must flow is determined ultimately by throttle position and vacuum slide height
Float System
Fuel enters the float chamber (3) by means of the inlet pipe and passage, through screen on the back of the inlet needle seat (4), and around the inlet needle (2)As the fuel fills the float chamber, the float (1) rises and forces the inlet needle against the seat, shutting off the orifice in the seatWhen fuel level is up in float chamber, floats are up and needle valve remains pushed up against valve seatUnder this condition, no fuel enters the float chamberAs the fuel level falls, floats go down and needle valve unseats itself to allow fuel into the chamberIn this manner, the needle valve releases and shuts off fuel alternately to maintain constant fuel level inside the float chamber