Hi; I dismantled there to be sure what I did in the past and found the screw a bit loose but UNF. I tested a BSF but did not worked. Would be very very frustrating tear up the cases to fix that but seems that I did the testing when I built that. Yes; there are UNF taps here.
I removed the magneto to check that but I do not think that an UNF tap into a BSF thread can make for a good tight hold for the taper of the magneto to the camshaft; anyway was UNF and had the UNF bolt there so was all good.