As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ANNUAL INSPECTION, PERFORMED A COMPRESSION CHECK ON ALL ENGINE CYLINDERS. TWO CYLINDERS FAILED THE CHECK LEAKING BY THE VALVES. REMOVED CYLINDERS, DISASSEMBLED. CHECKED VALVE SPRINGS INNER AND OUTER TENSION PER CONT OVERHAUL MANUAL USING A VALVE SPRING TESTER AND FOUND THAT THE INNER AND OUTER VALVE SPRINGS FAILED. TOTAL TIME ON THESE SPRINGS 910 SINCE NEW. REPLACED INNER AND OUTER VALVE SPRINGS WITH NEW SPRINGS AFTER CHECKING SPRING TENSIONS.