1984 Ski-Doo Shop Manual, Page 289Get this manual
SECTION 04 ELECTRICAL SYSTEM SUB-SECTION 03 (SPARK PLUGS)
SPARK PLUGS
NOTE: The 1984 Bombardier snowmobiles are using three (3) spark plug types, Bosch spark plugs, NGK spark plugs and Nippondenso 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 use The following charts will assist you in making the change-over easily and effectivelyIMPORTANT: The new code has different heat range identification systemHigh number Low number hot plug cold plug