As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A ROUTINE COMPRESSION CHECK, THE INTAKE VALVE WAS FOUND LEAKING ON THE NR 4 CYLINDER. THE CYLINDER WAS REMOVED AND THE INTAKE VALVE AND SEAT WERE REGROUND TO FIT EACH OTHER. SUBMITTER SUGGESTED POSSIBLE CAUSE AS IMPROPER ASSEMBLY PROCESS AT THE FACTORY.