As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOT REPORTED DEAD LEFT MAGNETO ON LT ENGINE OF ACFT WHILE PERFORMING RUNUP. THE DUAL MAGNETO WAS REMOVED AND IT WAS FOUND THAT THE LT DISTRIBUTOR GEAR HAD A LOT OF PLAY AT THE BEARING WHICH ALLOWED THE GEAR TO BECOME UNMESHED WITH THE ROTOR GEAR. THE DISTRIBUTOR GEAR BLOCK WAS REMOVED AND IT WAS FOUND THAT THE BRONZE TYPE BEARING TO BE VERY LOOSE IN THE DISTRIBUTOR GEAR BLOCK.