1986 Ski-Doo Factory Shop Manual, Page 365Get this manual
Section 04 ELECTRICAL Sub-section 02 (IGNITION TIMING)
5Look through inspection hole and check jf flywheel
mark align with center mark on crankcase(except on 503 type)
The ignition components are affected by temperature variationtherefore, timing must be checked when engine is coldafter MAXIMUM 20 seconds idling
All engines except 503 type
1Connect timing light pick-up to the spark plug lead (mag
side on twin cylinder enginesL Connect tachometer to the yellow and vellowblack wires of magneto+Flywheel mark Flywheel mark should aUgn with crankcase center mark
WARNING: Place ski tips against wallraise rear of vehicle on stand so that track does not contact thegroundMake sure no one passes behind the vehicle while engine is runningKeep clear of track and other moving parts
NOTE: Use separate battery to supply timing light (except on electric starting models)
Turn headlamp "ON" when checking the timing,
2Start the engine and point timing light straight In line
with the crankcase timing mark, Bring engine to 6000 R.P,Mfor brief instant