Background
The aircraft sustained damage during an off-airport landing after the engine lost power. The pilot stated that the aircraft was being operated using automotive fuel, which did not have the required supplemental type certificate.
Findings
At the time of the incident, the aircraft had not undergone the mandatory annual inspection. Additionally, the engine had exceeded its recommended time between overhauls (TBO) by more than 19 percent.
Post-Accident Examination
A post-accident examination of the engine revealed that the number 3 exhaust valve had broken off, and this failure caused a portion of the top of the piston to break out.
The source provides no further details.