Good point. The magnet looks pretty rusty and could use a good brushing. As for the gap, i'm not sure what the proper size is supposed to be. My Pepere taught me just to use a piece of paper folded in half... its worked on every B and S engine i've worked on so far!! ?may not help even if it measures right, the secondary may be jumping a small gap between wires internally and not actually shorted as you think of it. Was the air gap clean and correct? I have heard of filings getting picked up over time and shorting the air gap out as to proper magnetism.
Leave the magnet aloneGood point. The magnet looks pretty rusty and could use a good brushing. As for the gap, i'm not sure what the proper size is supposed to be. My Pepere taught me just to use a piece of paper folded in half... its worked on every B and S engine i've worked on so far!! ?