1980 Ski-Doo Shop Manual, Page 216Get this manual
SECTION 04 SUB-SECTION 06 (SPARK PLUGS)
HEAT RANGE
The proper operating temperature or heat range of the spark plug is determined by the spark plug's ability to dissipate the heat generated by combustionThe longer the heat path between the electrode tiP to the plug shell, the hotter the spark plug operating temperature will beand inversely, the shorter the heat path, the colder the operating temperature will beA "cold" type plug has relatively short insulator nose and transfers heat very rapidly into the cylinder head, Such plug is used in heavy duty or continuous high
speed operation to avoid overheating
FOULING
Fouling of the spark plug is indicated by irregular running of the engine, decreasmg engine speed due to misfiring,
reduced performance, and increased fuel consumption
This is due to loss of compressionOther possible causes are: prolonged idling, running the engine with the choke
on, or running on too rich mixture due to faulty carburetor adjustment or incorrect fuel andor fuel mix-
ing, The plug face of fouled spark plug has either dry coating of soot or an oily, glossy coating given by