2003 Polaris Deep Snow Snowmobiles Service Manual, Page 159Get this manual
FUEL SYSTEMCARBURETION 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; plug fouling -Heavy exhaust smoke -Engine runs worse after warm up -Engine "loads up" -Spark plug electrodes white -Fluctuation in engine speed -Power loss -Engine overheats -Cylinder scoringHoling pistons -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 conditionsworn belt