Fuel / Exhaust
4.17
Car buretor Pop--Off Valve Testing
If operating pop off pressure is too high, the amount of fuel available to the engine will be reduced, causing a lean
condition.
High pop off pressure may be caused by:
S Restricted fuel inlet passage
S Inlet needle stuck in seat
S Corrosion on lever arm, lever arm pin, and/or return spring
S Incorrect lever arm return spring (Use only genuine Polaris parts)
S Fuel return line orifice missing
Testing Needle and Seat Pop Off Pressure
1. Pressure test each carburetor individually. To provide accurate readings remove the regulator diaphragm
and its cover before testing. Wet the needle with WD40t or a similar substance. NOTE: Do not use gasoline
due to the hazard of fire. Protect your eyes from the spray when the needle valve “pops off”.
2. Remove the fuel lines connecting the carburetors.
3. Attach the Mity Vact to the fuel inlet fitting of the carburetor to be tested.
4. Plug the fuel return outlet of the carburetor to be tested.
5. Pressurize the carburetor with the pump until the needle valve pops off. Pump slowly and note the pressure
when the valve opens. Test the valve at least three times to ensure an accurate reading. Be sure to keep the
needle valve wet. NOTE: The reason for wetting the needle valve is to duplicate actual conditions during
operation. When the engine is running, the needle valve has fuel running through to wet it and engine
vibrations to help the needle obtain a good seal.
Apply 10-18 PSI. The carburetors should hold pressure at no less than 5-8 PSI. Otherwise see pop off pressures
listed in the specifications in the beginning of this section. If the carbs do not hold pressure, needle and/or seat
leakage is evident.
Individual Test
Attach pump to fuel inlet.
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