On January 31, 2007, approximately 1010 Pacific standard time, an experimental Martin/Harris Harmon Rocket, N141RH, experienced a collapse of the main landing gear during a power-off forced landing on a residential street about one mile west of Portland-Troutdale Airport, Troutdale, Oregon. The private pilot, who was the sole occupant, received minor injuries, and the aircraft, which had been purchased by the pilot one day prior to the accident, sustained substantial damage. The 14 CFR Part 91 personal pleasure flight, which was en route to Portland-Troutdale Airport, was being operated in visual meteorological conditions. The aircraft departed Auberge Des Fleurs airstrip, near Sandy, Oregon, about 10 minutes prior to the accident. No flight plan had been filed. According to the pilot, the engine started to run rough almost immediately after takeoff, but after switching fuel tanks and turning the boost pump on, he was able to get it to run smoothly. Since he did not want to make his first landing in the recently purchased aircraft at the small field that he had just departed from, he decided to head for Portland-Troutdale Airport, which he figured was a little over five minutes away. As he neared the airport, the engine began to run only intermittently, and eventually stopped running altogether. It then started again, and ran at almost full power for about 15 seconds, and then quit again. The pilot initially thought he may be able to stretch the glide to the airport, but soon realized he was not going to make it that far without power. He therefore attempted a forced landing on a residential street within a development of single-family homes. During the landing sequence the aircraft experienced a collapse of the main landing gear, and sustained further damage when it contacted the curb of the street. During the post-accident inspection by an FAA airworthiness inspector, particles of fuel tank sloshing compound were found in the gascolator filter screen, but no contamination was found in the fuel or in the fuel system anywhere downstream from the gascolator. A further inspection of the engine and fuel system found no anomalies that would have contributed to the loss of power, and according to the pilot, the aircraft had between 15 and 19 gallons of fuel onboard at the beginning of the 10 minute flight. According to Lycoming's engine specification data, the engine would normally consume between 11 and 16 gallons per hour, depending on ambient conditions and how it was operated. At the termination of the inspection and testing, no clear reason for the loss of power could be established.