As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING GROUND RUN, MAGNETO CHECK WAS PERFORMED A PER ENGINE RUN-UP LIST. WHEN THE RIGHT MAG WAS SELECTED, THE RIGHT ENGINED DIED. INVESTIGATION REVEALED THAT THE MAIN POINT CAM FOLLOWER WAS BROKEN OFF AND MISSING. MAGNETO WAS REPLACED.