As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING START, PILOT NOTICED THE ENGINE RAN VERY ROUGH. SHUTDOWN ENGINE AND RESTARTED IT. ENGINE RUNNING SMOOTHER, BUT A VIBRATION WAS NOTED. ENGINE SHUTDOWN AND MECHANIC INVESTIGATED. A COMPRESSION CHECK WAS TAKEN AND NR 3 CYLINDER COMPRESSION WAS 0/80 WITH ALL THE AIR LEAKING PASSED THE EXHAUST VALVE. MECHANIC ATTEMPTED TO PERFORM SB388C ON NR 3 CYLINDER. EXHAUST VALVE TO GUIDE CLEARANCE COULD NOT BE MEASURED DUE TO THE VALVE BEING STUCK. THIS CYLINDER IS NOT SERVICEABLE AT THIS TIME.