1980 Ski-Doo Shop Manual, Page 214Get this manual
SECTION 04 SUB-SECTION 06 (SPARK PLUGS)
SPARK PLUGS
SPARK PLUG NUMBERING SYSTEM
Bosch has introduced new numbering code for its
1980 CROSS REFERENCE CHART
List of Bosch' spark plugs used on Bombardier snowmobiles: NEW NUMBER M4A2 M7A W3C W2C OLD NUMBER M240T1 175T1 W275T2 W300T2