As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BYPASS VALVE REMOVED TO COMPLY WITH LYCOMING SB 518A. THE NUT WAS FOUND LOOSE AND HALF-WAY UNSCREWED FROM THE THREADED SHAFT OF THE VALVE. IT WAS NOTED THE S/N OF VALVE WAS HIGHER THAN THE AFFECTED S/N'S LISTED IN SB. SUBMITTER RECOMMENDS INSPECTION PER SB OF ALL VALVES REGARDLESS OF S/N'S SB SHOULD BE AMENDED OR AN AD ISSUED.