NTSB Probable Cause

IMPROPER EMERGENCY PROCEDURES BY THE PILOT, WHEN HE INADVERTENTLY SHUT DOWN THE LEFT ENGINE AFTER ENCOUNTERING A PARTIAL LOSS OF POWER IN THE RIGHT ENGINE. FACTORS RELATED TO THE ACCIDENT WERE: IMPROPER INSTALLATION OF THE RIGHT ENGINE'S #6 EXHAUST VALVE SEAT BY OTHER MAINTENANCE PERSONNEL, FATIGUE FAILURE OF THE #6 EXHAUST VALVE, AND THE PILOT'S LACK OF FAMILIARITY WITH THE AIRCRAFT.