As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAKEOFF, AIRCRAFT ENGINE BECAME VERY ROUGH. PILOT COULD NOT DUPLICATE ON GROUND. FURTHER INVESTIGATION FOUND NR 1 AND NR 2 CYLINDER EXHAUST VALVES STICKING. REMOVED AND CLEANED ALL FOUR CYLINDER EXHAUST VALVES AND GUIDES. THIS IS SECOND OCCURRENCE WITH THIS ENGINE.