1970-1979 Ski-Doo Snowmobiles Service Manual, Page 32Get this manual
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PERIODIC MAINTENANCE AND TUNE-UP Table Engine IGNITION TIMING SPECIFICATIONS Indirect Timing BTDC'
0.035-0.055 in(0.90-1.40mm) 0.037-0.057 in(0.95-1.45mm) 0.147-0.167 in(3.73-4.23mm) 0.077-0.097