1969 Ski-Doo Snowmobiles Service Manual, Page 91Get this manual
In yet another case, plug of lower heat value (hotter plug) may prove advantageous: provided vehicle in good order is only driven slowly with frequent stopsThis especially applies
to high-powered vehicles with high top speed, whose power reserve is only rarely used, as for instance, when acceleratingIn continuous driving at low engine speed, and at light loads, with frequent idling etc the air-fuel mixture is always rather rich, and oil entering the combustion chamber does not always burn away entirelyIt may be an advantage to
fit hotter plug, i.eone with lower heat value than that specified by the makersThis applies in particular to