1972 Ski-Doo Shop Manual, Page 203Get this manual
3-03-01 Electrical
SPARK PLUGS
GENERAL
In the Bombardier-Rotax engine, the ignition voltage generated by the magneto ignites the air-fuel mixture contained in the combustion chamberIt is the function of the spark plug to introduce the ignition current into the combus tion chamber and to initiate the combustion of the compressed air-fuel mixture by spark jumping across the spark plug electrodesA Pyrit Insulator Shrink fined shell lectrica"y Conductlve Compound Internal Gasket Permanent aasket Thread Center electrode Ground ElectrOde Air Space Insulator Tip Breathinll Space Terminal Nut
PLUG DESIGN
A design for universal spark plug suitable for all engines is impossible because of the consid erable differences in operating conditions; type of engine, compression ratio, rotational speed, cooling arrangements, carburetor setting and fuelA correctly selected spark plug is defined to certain temperature rangeThis temperature range is sufficient to bum off any particles of oil or soot deposited on the plug tip without the occurrence of pre-ignitionIt is only in cases where inevitable deposits form and become electrically conductive that the spark plug temperature range is impaired and misfiring andor fouling occurs