As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON ENGINE INSPECTION RUN-UP MAGNETO RPM DROP NORMAL. WHEN MECHANIC ATTEMPTED TO CHECK TIMING, FOUND TIMING 20 DEGREES LATE. REMOVED AND DISASSEMBLED MAGNETO. FOUND DISTRIBUTOR CARBON BRUSH MISSING AND ROTOR SHAFT BROKEN AT BASE OF SLOT FOR POINT CAM. ALSO FOUND EXTENSIVE BURNING DAMAGE TO DISTRIBUTOR BLOCK CROSSBEAM AND ARCING DAMAGE TO COIL AND DISTRIBUTOR GEAR SHAFT.