2002 Ski-Doo Shop Manual Volume Three, Page 246Get this manual
Section 06 ELECTRICAL Subsection 02 (IGNITION TIMING)
IGNITION TIMING
377 and 503 Engine Types If for any reason, ignition timing accuracy is suspected, it can be verified as followsIMPORTANT: For ZX fan models1 2
Verifying Magneto Flywheel Timing Mark Position