As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON APPROACH INTO KCPR FROM U68 THE PILOT OBSERVED ENGINE BEGAN TO RUN ROUGH FOLLOWED BY EGT AND CHT TEMPERATURES DRASTICALLY INCREASE. THE PILOT LANDED AT KCPR WITHOUT INCIDENT. MAINTENANCE REPLACED BOTH MAGNETOS AND OPS CHECK GOOD. UPON TEARDOWN OF MAGNETOS, EDWARDS JET CENTER MAINTENANCE (KBIL) FOUND 25% OF THE TEETH ON THE DRIVEN PLASTIC MAGNETO DISTRIBUTER GEAR MISSING, ON THE RH MAGNETO.