1979 Ski-Doo Supplementary Shop Manual, Page 112Get this manual
SECTION 04 SUB-SECTION 04 (IGNITION TIMING )
EDGE GAP VERIFICATION
By following either of the procedures mentioned herein the edge gap will automatically be adjusted However, if the edge gap is to be verifiedproceed as follows: From timing marks, rotate magneto clockwise 1 of turnHold advance mechanism centrifuga weight in the open position (toward magneto rim) then slowly turn magneto back counter-clockwise until timing light fluctuates or until tone signal sound level varies
At this point check the distance between pole shoe trail ing edge and magnet (edge gap), with strip of card board of appropriate width(Refer to the following table Engine type Edge gap 7-11 mm 1.275430")