As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE DISPLAYED EXCESSIVE MAG DROP DURING PRE-FLIGHT RUNUP. MAGNETO REMOVED FOR INSPECTION. IMPULSE COUPLING SPRING FOUND INCORRECTLY INSTALLED IN HOUSING RESULTING IN DAMAGE TO HOUSING. IMPULSE COUPLING FAILED MANDATORY INSPECTION REQUIREMENTS IN SERVICE MANUAL L1363D. IMPULSE COUPLING REMOVED FROM SERVICE AND REPLACED WITH NEW UNIT. CARBON BRUSH INSTALLED INCORRECTLY, CARBON BRUSH REMOVED AND REPLACED WITH NEW BRUSH.