Polaris 2001 High-Performance Snowmobile Service Manual (PN 9916690), Page 169Get this manual
CARBURETION Troubleshooting
Fuel system diagnosis should follow specific path, first examining the fuel tank, then the filters, fuel lines, vent lines, fuel pump, impulse hose, air box, exhaust system and finally the carburetorsThe following troubleshooting information assumes that the general mechanical condition of the engine (pistons, rings, bearings, etc is goodWhen the fuelair mixture is diagnosed as improper due to spark plug readings, clean the carburetor and blow its passages clear with compressed airUse the spark plug firing end condition as guide for further determination of whether the mixture is too rich or too leanUse the throttle lever to determine at what degree of throttle valve opening the problem existsCONDITION Mixture Too Rich SYMPTOMS -Black spark plug tip -Heavy exhaust smoke -Engine runs worse after warm up -Runs better without air silencer -Combustion chamber has heavy deposits of carbon -Spark plug electrodes white -Fluctuation in engine speed -Power loss -Engine overheats -Cylinder scoring -Backfiringdetonation -Throttle diagnostic opening check points -Incorrect ignition timing -Improper track tension (too tight) -Incorrect carburetor jetting -Fuel leaks (lines, fittings, fuel pump) -Needle and seat leaks -Plugged exhaust -Carburetor vent line problems -Clutching incorrect for conditions