As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CYLINDER OVERHAUL A DAMAGE SEAT POCKET CUTTER USE USED. THIS RESULTED IN A VALVE SEAT POCKET THAT MEASURED WITHIN LIMITS BUT LACKED THE PROPER SURFACE CONTACT. AFTER APPROXIMATELY 3 HOURS OF ENGINE OPERATION, THE VALVE SEAT CAME OUT CAUSING THE INTAKE VALVE TO BREAK. THIS CAUSED A LOSS OF ENGINE POWER AND THE HELICOPTER MADE A HARD LANDING. HELICOPTER WAS DESTROYED BY FIRE. (K)