XS750AU
Coast to Coast
Don't have an XT500, but from your previous photo it looks like
Refer to attached photo.
Loosen screws A & B (do not remove)
Use a blade screw driver in position C to then rotate the ignition base plate to advance or retard the spark timing (not sure which way retards or advances but you will soon work it out)
If you leave enough drag on the screws A & B then you should be able to tune the timing while the motor is going, which makes it easier!
Hope this helps.
Refer to attached photo.
Loosen screws A & B (do not remove)
Use a blade screw driver in position C to then rotate the ignition base plate to advance or retard the spark timing (not sure which way retards or advances but you will soon work it out)
If you leave enough drag on the screws A & B then you should be able to tune the timing while the motor is going, which makes it easier!
Hope this helps.