As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE AIRCRAFT TAXIED OUT TO FLY. THE PILOT DID HIS RUN UP AND FOUND THE ENGINE WOULD NOT RUN ON JUST THE RIGHT MAGNETO. PILOT RETURNED AIRCRAFT AND DID NOT FLY. I CONFIRMED THE DISCREPANCY AFTER A RUN UP. I REMOVED AND DISASSEMBLED THE MAGNETO AND FOUND THE ROTOR GEAR WITH THE BROKEN ROTOR ATTACH POINTS STILL IMBEDDED IN IT FLOATING INSIDE THE MAGNETO. THE MAGNETO ROTOR PN M3158 END THAT HOLDS THE ROTOR GEAR PN M3827 BROKE AT THE ROTOR GEAR ATTACH POINTS. BOTH ATTACH POINTS BROKE.