1985 Ski-Doo snowmobile Service Manual, Page 347Get this manual
Section 04 ELECTRICAL SYSTEM Sub-section 03 (SPARK PLUGS)
SPARK PLUGS
NOTE: The 1985 Bombardier snowmobiles are using two (2) spark plug brands, Bosch spark plugs and NGK spark plugs
BOSCH SPARK PLUG TYPE
SPARK PLUG NUMBERING SYSTEM
Bosch has introduced new numbering code for its complete line of spark plugsThe new code is shorter, therefore easier to useThe following charts will assist you in making the change-over easily and effectively