1986 Ski-Doo Factory Shop Manual, Page 369Get this manual
Section 04 ELECTRICAL SYSTEM Sub-section 03 (SPARK PLUGS)
NGK SPA.RK PLUG TYPE All models except Elan
SPARK PLUG NUMBERING SYSTEM
Bombardier is using the NGK spark plug type on most of the 1986 snowmobile modelsThe heat range identification system is: High number ,cold plug