As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE LEFT MAGNETO WAS BEING REPLACED DUE TO DIFFICULTY STARTING THE ENGINE. THE TECHNICIAN DISCOVERED A SECTION OF THE MAGNETO MOUNTING FLANGE CRACKED AND SEPARATED AND SEPARATED FROM THE MAGNETO. THE CRACK EXTENDED THROUGH THE UNUSED IMPULSE COUPLING STOP HOLE AND CONTINUED IN A STRAIGHT LINE PARALLEL TO THE FLAT SIDE OF THE MAGNETO OUTER CASE (FRAME) FOR APPROXIMATELY THREE INCHES SEPARATING THE SECTION OF FLANGE. THE BROKEN SECTION WAS CENTERED ON THE MOUNTING STUD LOCATION.