On October 6, 2015, at 1830 central daylight time, an unregistered Refling RV8, collided with a tractor during an off airport forced landing following a loss of engine power in Bottineau, North Dakota. The commercial pilot was not injured. The airplane sustained substantial damage to the wings and fuselage. The unregistered aircraft was operated by the builder, a private individual, under the provisions of 14 Code of Federal Regulations Part 91 as a test flight. Visual flight rules conditions prevailed for the flight, which was not operated on a flight plan. The local flight originated from the Bottineau Municipal Airport (D09), Bottineau, North Dakota, about 1800. The purpose of the flight was to seat the piston rings on the new engine. The pilot was also the aircraft builder. He stated the engine had about 19 minutes of ground run time on it prior to the flight. The pilot planned to make five 34-mile circuits around the extended runway centerline at an altitude of 5,000 feet. The pilot stated that during the fourth circuit, while on an extended downwind, he detected the odor of fuel in the cockpit. During the upwind leg of the fifth circuit at a point about 6 miles northwest of the airport, the engine power decreased to idle. The pilot attempted to diagnose the reason for the loss of power as he continued to fly away from the airport. At a point about 10 miles from the airport, he turned back toward the airport as he continued attempts to regain engine power. The airplane was about eight miles from the airport when total loss of engine power occurred. The pilot determined he was not going to be able to make it back to the airport, so he chose a field in which to make a forced landing. The pilot lost directional control of the airplane due to the rough terrain and the airplane contacted a parked tractor. The pilot stated that after the accident he determined that the fuel line between the mechanical fuel pump and the fuel injection servo was disconnected. The pilot stated that the engine was delivered to him with this fuel line installed; however, he did not check the tightness of the fuel lines after installing the engine on the airplane. The pilot/aircraft builder had just completed building the airplane and had not submitted the paperwork for the airworthiness certificate and aircraft registration.