1970-1979 Ski-Doo Snowmobiles Service Manual, Page 50Get this manual

1970-1979 Ski-Doo Snowmobiles Service Manual, Page 50

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TROUBLESHOOTING Ignition Timing
Preignition is caused by excessive heat in the combustion chamber due to spark plug of improper heat range andor too lean fuel mixtureSee Figure for an example of