As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED AN INOPERATIVE MAGNETO ON PREFLIGHT RUN UP. WHEN THE MAGNETO WAS REMOVED IT WAS NOTICED THAT THE ENDS OF THE PN 531178, DRIVE COUPLING RETAINER WERE MISSING, AND APPARENTLY WERE INGESTED DOWN INTO THE ENGINE ACCESSORY SECTION. THE MAGNETO WAS REMOVED AND DISASSEMBLED. IT APPEARS THAT THE BEARING, PN 10-353060 HAD FAILED. THIS MAGNETO WAS 150 HRS AWAY FROM THE NEXT 500HR INSPECTION. THE ENGINE WAS R & R BY A FACTORY REMANUFACTURED ENGINE.