1985 Ski-Doo snowmobile Service Manual, Page 350Get this manual
Section 04 ELECTRICAL SYSTEM Sub-section 03 (SPARK PLUGS)
DESIGN SYMBOLS USED IN NGK SPARK PLUGS
First letter prefix for thread and hexagon size Secondthird letter prefix for construction feature, except single prefix Heat rating number First letter suffix for thread: reach Second letter suffix for construction feature, etc'or Honda vehtcles
Hel(agon
Thread size
Construction feature
Thread reach
Construction leature, etc
25.4 mm 20.6 mm
16.0mm 18,Omm 23.8 mm
Hexagon size 20.6 mm Hexagon size 16.0 mm Hexagon size 23.8 mm Compact type (SHOATY) Compact type (BANTAM)
P,Oj8Ctad InSL:laIO! nose type
120mm Ithread d"
Specials Spedal
Uhread dill None
Competition type
10mm 12 mm
Racing plugscenter electrode of nickel alloy
225 mm UNClad dr Pf :2" 14mm)
Racing plugscenter alectrode of precious metal Racing plugs, nickel