As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE RAN ROUGH AT IDLE AND LOUD MECHANICAL NOISES WERE REPORTED. VISUAL INSPECTION OF ENGINE BEFORE DISASSEMBLY SHOWED ZERO VALVE STEM TO ROCKER CLEARANCE. DISASSEMBLY OF CYLINDER SHOWED EXHAUST VALVE PN AL19001 WORN EXCESSIVELY IN THE RETAINER GROOVE. RECOMMEND REPLACEMENT OF EXHAUST VALVE.