As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON REMOVAL OF CYLINDER NR 1, THE INNER VALVE SPRING P/N 631521 AND OUTER VALVE SPRING P/N 637837 WERE FOUND BROKEN. THE OUTER VALVE SPRING P/N 637837 ON CYLINDER NR 3 WAS FOUND BROKEN. CAUSE IS UNKNOWN. OWNER COMPLAINED OF EXCESSIVE ENGINE VIBRATION.