2000 Polaris Indy 500 / 600 snowmobile service manual, Page 136Get this manual
FUEL SYSTEMCARBURETION Slide Cutaway (18-38 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 angle(Leaner mixture)