As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ON RETURN FLIGHT THE LT ENGINE STARTED TO RUN ROUGH. UPON LANDING THE PILOT DID A MAGNETO CHECK AND FOUND THAT THE MAGNETO DROP WAS EXCESSIVE. REMOVED MAGNETO WITH COVER OFF FOUND METAL IN BACK OF MAGNETO. INSTALLED OVERHAULED MAGNETO, GROUND RUN AIRCRAFT NO FAULTS FOUND.