2008 Polaris ATV Predator 50, Sportsman Outlaw 90 Service Manual, Page 95Get this manual
FUEL SYSTEM Pilot System (Idle38 Throttle)
The pilot system's main function is to meter fuel at idle and low speed drivingThough its main function is to supply fuel at low speed, it does feed fuel continuously throughout the entire operating rangeFuel for the pilot jet is drawn from the float bowl, mixed with air regulated by the air screw, and delivered to the engine through the pilot outletThe mixture is regulated to some degree by adjusting the air screwWhen the air screw is closed, the fuel mixture is made richer as the amount of air is reducedWhen the air screw is opened, the mixture is made more lean as the amount of air is increasedGeneral Carburetor Representation Cutaway Angle
Slide Cutaway (1838 Throttle)
Throttle valve cutaway effect is most noticeable at 14 throttle openingThe amount of cutaway is pre-determined for given engine to maintain 14:1 airfuel ratio at part throttleA steep angle would indicate fairly lean mixture because there is less resistance to air flowA flat angle would provide much richer mixture because there is more resistance to air flowThe venturi shape can be adjusted for each engine's breathing characteristics by using different valve cutaway angleA number will be stamped into the bottom of the valve (e.g2.5) indicating the size of the cutawayThe higher the number, the steeper the angleGeneral Carburetor Representation