As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED INOPERATIVE MAGNETO ON REAR ENGINE, LEFT POSITION. MECHANIC REMOVED MAGNETO AND FOUND THE LEFT CRANKSHAFT IDLER GEAR ASSEMBLY WORN OUT AND ENGINE OIL SUMP SUCTION FILTER CONTAMINATED WITH METAL PARTICLES. ENGINE CHANGED.