1978 Ski-Doo Shop Manual, Page 228Get this manual
SECTION 04 SUB-SECTION 04, (IGNITION TIMING)
354 ENGINE TYPE
Timing procedure for this engine type is composed of four main phases, all being equally important: 1Position of the armature plate 2Position of the timing marks on magneto ring 3Air gap between trigger coil and magneto ring 4Timing verification using stroboscopic timing1To obtain best generator coil performance, position the armature plate on the crankcase with the retaining cap screw in the middle of the plate slots
II Crankcase central mark