Magneto timing with one p-mag

I have one p-mag and one slick. I'm using a standard buzz box to check the timing on the slick mag. I'm not sure what to do with the other lead. The buzz box buzzes constantly since one of the leads is not connected to a magneto.

Can I simply use the light on the buzz box for the lead connected to the magneto. i.e. Does the light come on at the same time the buzz would happen for the magneto?

The magneto was overhauled last year. Using the light, the timing has slipped by about 2 degrees since last year. (60 hours) Is that normal for a newly overhauled magneto?

Thanks,
Michael-

You can just connect the other lead to ground so it stays quiet. The light and the beep/buz come on at the same time, which should happen at base timing on cylinder 1. Slipping 2 degrees isn?t unheard of, but often they don?t change at all. Keep your eyes on it. Maybe check it again at the next oil change and see if it has held. Timing change is usually a wear item rather than a moving mag. Sometimes they will ?wear in? like that.

If I recall, Slick recommends a 100 hour timing check and 2 degrees as the max amount of timing shift you should see with each check. As Jesse mentioned, they wear internally and some shift is normal but too much should be seen as a need to IRAN.