2005 Ski-Doo Tundra, Skandic, Expedition Shop Manual, Page 45Get this manual
Section 02 TROUBLESHOOTING GUIDE Subsection 01 (ENGINE (2-STROKE))
Symptom: ENGINE PINGING(cont'd)
5Check compression ratio- Compression ratio is too highReplace inadequate part(s) to obtain manufacturer's recommended compression ratio or use higher grade fuel