Accident Sequence
The pilot reported that the engine ran rough during a previous flight. He subsequently removed, cleaned, and replaced the spark plugs. On the next flight, after takeoff, the engine again began to run rough and intermittently when the aircraft was approximately seven miles from the departure airport. An emergency landing became necessary. During the landing in rough terrain, the nose gear broke, resulting in damage to the fuselage.
Investigation
An FAA inspector examined the wreckage and did not find any evidence to explain the reported power loss. In his report of the accident, the pilot stated that rubber particles, possibly from fuel lines, were found in the fuel. The aircraft was being operated on auto fuel.