"Teacherjh" wrote in message
...

If you get next to nothing on a mag during
runup, don't switch back to the good mag or you may blow out your
exhaust. Let the engine die or pull the power back to idle before you
switch back to a working mag.


Why? How? What about switching to "both"?

Switching to "both" would constitute switching back to a good mag.

As for the reason, it's because without either mag operating (one shorted
out on purpose, the other dead), a bunch of unburned fuel can accumulate
very quickly. Restart the fire by switching the good mag back on, and you
could wind up with a big fireball or exhaust fire.

That said, even having heard that advice before, the time that I found a
dead mag on a run-up, I completely forgot the advice and flipped the mag
switch back to both. It was a straight-forward reflex: if you don't like
what happened when you do something, restore back to the previous
configuration.

Fortunately, nothing bad happened.

Pete