1999 Polaris SLH, SLTH, SLX, SLTX, PRO785 Factory Service Manual, Page 93Get this manual
FUEL SYSTEMCARBURETION System OperationMikuni If operating pop off pressure is too high, the amount of fuel available to the engine will be reduced, causing lean conditionHigh pop off pressure may be caused by: Restricted fuel inlet passage Inlet needle stuck in seat Corrosion on lever arm, lever arm pin, andor return spring Incorrect lever arm return spring (Use only genuine Polaris parts) Fuel return line orifice missing
Testing Needle and Seat Pop Off Pressure
Individual pop off pressure testing
NOTE: Carburetors can be tested as set, but will only indicate the pop off pressure of the carburetor with the lowest pressure
Pressure test each carburetor individuallyTo provide accurate readings remove the regulator diaphragm and its cover before testingWet the needle with WD40TM or similar substanceNOTE: Do not use gasoline due to the hazard of fireProtect your eyes from the spray when the needle valve "pops off"Remove the fuel lines connecting the carburetorsAttach the Mity VacTM to the fuel inlet fitting of the carburetor to be testedPlug the fuel return outlet of the carburetor to be tested Pressurize the carburetor with the pump until the needle valve pops offPump slowly and note the pressure when the valve opensTest the valve at least three times to ensure an accurate readingBe sure to keep the needle valve wetNOTE: The reason for wetting the needle valve is to duplicate actual conditions during operationWhen the engine is running, the needle valve has fuel running through to wet it and engine vibrations to help the needle obtain good seal