On January 18, 2006, at 1225 central standard time, an experimental amateur-built Zilz Zenith CH801, N143ZT, collided with a power line pole and trees during an off airport forced landing in Moscow Mills, Missouri. The pilot was not injured. The airplane was substantially damaged. The Title 14 Code of Federal Regulations Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The flight originated from the Moscow Mills - Greenfield Airport (M71), Moscow Mills, Missouri, at approximately 1100. The pilot said the airplane was on its third flight since he completed building it. The purpose of the flight was to test and record engine performance at various power settings. He stated he had been flying for approximately one and a half hours when the fuel pressure dropped below 2 pounds per square inch (psi) and the engine stopped running. He stated he was able to restart the engine, but it failed to produce power. The pilot turned toward the airport, but he did not have enough altitude to make it back, so he elected to land in a pasture with a row of trees bordering the edge of the field. The pilot stated he did not see the power lines above the trees until he was at an altitude which was insufficient to clear the lines. He elected to fly through the tree line in order to avoid contacting the power lines. The airplane contacted a power line pole and trees prior to coming to rest in the field. A post accident examination of the airplane and engine was conducted by an inspector from the Federal Aviation Administration Flight Standards District Office in St. Louis, Missouri. The inspector reported that he was unable to find any failure/malfunction, which would have resulted in the loss of engine power. The pilot reported that he believes the loss of engine power was a result of vapor lock. He reported the gascolator was located near one of the exhaust pipes and that the loss of power occurred during a flight condition, which would have created reduced cooling through the engine cowling and increased exhaust temperatures.