2003 Ski-Doo ZX Series Factory Shop Manual, Page 255Get this manual
Section 06 ELECTRICAL Subsection 02 (IGNITION TIMING)
NOTE: Between 3000 and 4000 RPM, the spark advance does not changeSo when checking ignition timing at 3500 RPM, change in engine speed within 500 RPM will not affect the timing mark when checked with the timing light
Scribing Timing Mark
1Clean the area around the MAG spark plug, and remove it2Install the TDC gauge in the spark plug hole, (magneto side) and adjust as follows: aPosition the MAG piston at approximately TDC
dPosition the dial face toward the PTOMove the gauge down until the needle just begins to move, then move down further or mm (approximately 14 in)Tighten adaptor lock nut by hand3Locate the piston TDC position as follows: aSlowly rotate the drive pulley back and forth across TDC while observing the needleNote that the needle stops moving only as the piston is changing directionbRotate the dial face so that "0" is in line with the needle when it stops movingcAgain, slowly rotate the drive pulley back and forth across TDC and adjust the dial face to "0", until the needle always stops exactly at "0" before changing directiond"0" now indicates exact TDC4Rotate the drive pulley clockwise, one-quarter turn then carefully rotate it counterclockwise until the needle indicates the specified measurement, indicated in TECHNICAL DATA5Twist wire as shown and use it as pointerInstall the wire on upper starter bolt