1980 Ski-Doo Shop Manual, Page 151Get this manual
SECTION 03 SUB-SECTION 03, (IGNITION TIMING)
EDGE GAP VERIFICATION
By following either of the two procedures herein mentioned the edge gap will automatically be adjustedHowever, if the edge gap is to be verified, proceed as follows:
From timing marks, rotate magneto clockwise
(for 247 engine type hold advance mechanism centrifugal weight in full advance position (toward magneto rim)), then slowly turn magneto back counter-clockwise until timing light fluctuates or until tone signal sound level IncreasesAt this point check the distance between generator coil end and magnet (edge gap)with cardboard strip of appropriate width