As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ROUGH RUNNING ENGINE DURING POWER TRANSITION FROM CLIMB TO CRUISE. PILOT PERFORMED A FORCED LANDING INTO A FIELD. INVESTIGATION REVEALED A CLAMPING BOLT WHICH ATTACHES THE ROCKER BRACKET TO CYLINDER HEAD NR 4 HAD FAILED. NTSB ACCIDENT NUMBER WPR12LA275.