1999 Ski-Doo Factory Shop Manual Volume One, Page 83Get this manual
Section 03 TROUBLESHOOTING Subsection 05 (ELECTRICAL SYSTEM)
SYMPTOM CONDITION TestInspection
FOULED (BLACK) SPARK PLUG TIPNORMAL USE1Check carburetor(s)aCarburetion is too richAdjust according to specifications (refer to TECHNICAL DATA 10)2Check injection oil consumptionaInjection pump flow is too highAdjust according to specification or replace3Check oil qualityaPoor oil quality that creates depositsUse Bombardier oil4Check engine compressionaLeaking piston ring(s)Replace
SYMPTOM CONDITION TestInspection