1983 Ski-Doo Shop Manual, Page 203Get this manual
SECTION 04 ELECTRICAL SUB-SECTION 02 (IGNITION TIMING)
377, 503, ENGINE TYPES
Two methods are detailed in this section, the first using Top dead center gauge, the second using stroboscopic timing light
Stroboscopic timing light
NOTE: Timing can be checked using stroboscopic timing light (Snap-On MT 212 or Electro Speciality, model 978)The ignition components are affected by temperature variation, therefore, timing must be checked when engine is cold after approximately 20 seconds idling
Top dead center gauge verification
Remove the spark plugsOn 503 models, remove the fan cover
NOTE: (On Blizzard 5500 MX)The only way to remove the fan cover without damage is to slide it against the muffler in forward directionReverse procedure at installation+
WARNING: Ensure the engine is cold before fan cover removal on 503 models
Connect timing light pick-up to magneto side spark plug lead (on manual start models use separate battery to supply timing light)WARNING: Place ski tips against wall, raise rear of the vehicle on stand so that the track does not contact the groundMake sure no one passes behind the vehicle while engine is runningKeep clear of track and other moving parts