As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING PREFLIGHT RUN-UP RT ENG, RT MAGNETO EXPERIENCED EXCESSIVE DROP AND WAS RUNNING ROUGH. UPON INVESTIGATION OF THE MAGNETO IT WAS FOUND THAT THE DISTRIBUTOR GEAR BUSHING HAD WORN IN THE DISTRIBUTOR BLOCK HSG CAUSING A MISS FIRING CONDITION. MAGNETO WAS REPLACED.