As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(AU) DURING DOWN WIND LEG, THE ENGINE BEGAN TO RUN ROUGH. A FORCED APPROACH AND LANDING, NR 2 CYLINDER INTAKE PUSH ROD AND TUBE WERE BENT. THE COVER WAS REMOVED AND THE EXHAUST VALVE ROCKER ARM STUD WAS FOUND TO HAVE WORKED LOOSE. THIS ALLOWED THE CAP FROM THE EXHAUST VALVE STEM TO FALL OUT. IT IS SUSPECTED THIS CAP JAMMED THE INTAKE VALVE CAUSING THE ROD TO BEND.