As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A ROUTINE 50-HOUR OIL CHANGE COMPRESSION CHECK, EXCESSIVE LEAKAGE WAS FOUND LEAKING PAST THE INTAKE AND EXHAUST VALVE ON THE NR 1 CYLINDER. THE CYLINDER WAS REMOVED AND FOUND TO HAVE A WORN OUT EXHAUST VALVE AND GUIDE. IT ALSO HAD A BROKEN OUTER SPRING ON THE INTAKE VALVE AND NO CHOKE LEFT IN THE CYLINDER. POSSIBLE CAUSE; DEFECTIVE PARTS AND ASSY PROCECURES USED DURING REMANUFACTURING PROCESS.