As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON INITIAL POWER-UP FOR THE FLIGHT''S TAKEOFF ROLL, THE ENGINE LOST SUBSTANTIAL POWER. THE PILOT ROLLED OFF TO A TAXIWAY AND SHUT DOWN. AFTER TROUBLESHOOTING THE IGNITION SYSTEM, THE RIGHT MAGNETO WAS FOUND DEFECTIVE AND REPLACED WITH NEW. RUN-UP SATISFACTORY. (X)