On June 30, 2017, about 1238 eastern daylight time, an experimental, amateur-built KR2, N269HJ, was destroyed following a collision with terrain at Skypark Estates Airpark (18FD), Baker, Florida. The commercial pilot was seriously injured. The airplane was operated by the pilot under the provisions of 14 Code of Federal Regulations part 91 as a personal flight. Day, visual meteorological conditions prevailed, and no flight plan was filed for the local flight that was originating at the time of the accident.The pilot reported the that he was preparing for a local flight as part of the 40-hr phase I test period. The airplane had a total of 12 hours accumulated time and he was the registered builder of the airplane. The preflight operations were normal, he performed an engine run-up, and taxied to the end of the runway for departure. The fuel tank contained 10 gallons of fuel. The takeoff was normal until about half way down the runway, when the engine "sputtered and hesitated" and lost power. He was past the point where he could land on the runway, so he looked for a place to perform a forced landing. He initiated a right turn to avoid nearby houses, but, the wind was out of the north and pushed him to the left. He steepened the turn; however, he realized he needed more power to remain airborne. He stated that the engine never stopped running, but it was not producing enough power. He did not recall the actual impact due to his injuries. The pilot held a commercial pilot certificate for rotorcraft and gyroplane. He did not hold an airplane single-engine landrating. He stated in an interview that he was ready to take his sport pilot certificate check ride; however, he was unable to complete it due to weather cancelations. He reported 2,000 hours total flight time, including 500 hours in "ultralights." A witness was on the airfield and observed the airplane as it took off on runway 27. About 300 to 500 ft agl, after takeoff, the engine sputtered and changed sound. This occurred as the pilot began a 45º climbing turn to the right. The pilot then began a "tight" turn to the left and the airplane descended toward the ground. The witness reported that the engine appeared to be running throughout the accident sequence and may have been near idle power during the descent. An inspector with the Federal Aviation Administration (FAA) responded to the accident site and examined the wreckage. The wings separated from the airframe and were found fragmented. The engine, firewall, and propeller separated from the forward fuselage. The empennage remained attached to the aft fuselage. There was no fire. The engine was examined by an FAA inspector and a representative from the engine manufacturer. The engine exhibited impact damage predominantly on the under and left sides. The two-blade, fixed pitch, wooden propeller remained attached to the hub and the hub remained attached to the crankshaft. The propeller blades were shattered into numerous pieces. The carburetor exhibited impact damage. It was broken free from the induction system and the inlet fuel line was separated. The throttle control arm was found loose on the throttle control shaft; however, there was impact damage to the area and the pre-accident condition could not be determined. The carburetor was disassembled, and the internal components were undamaged. The fuel inlet screen was clean. The left magneto remained attached to the engine with impact damage evident to the distributor section. When rotated manually, it would produce spark on one post. It was removed and examined; the distributor was impact-damaged, and the distributor gear was displaced from impact forces. The right magneto was undamaged and remained attached to the engine. It was rotated manually and produced spark on all leads and in the correct order. The top spark plugs were removed for examination. The bottom spark plugs exhibited impact damage. The top plug electrodes exhibited minimal wear and light gray color when compared to a Champion inspection chart. The engine was rotated manually; internal continuity was confirmed, and compression and suction were observed on the No. 1 and No. 3 cylinders. Internal inspection of the cylinder components revealed normal operating and wear signatures. The No. 2 cylinder exhibited impact damage. Further disassembly revealed a fractured mounting stud under the intake valve and the exhaust valve was stuck in the open position. The mounting stud was determined to be from the carburetor and showed signatures of separation during the impact sequence. The exhaust valve was removed and was bent from impact. The No. 4 cylinder also exhibited impact damage to the head with damage to the valves. Other than impact damage, the internal components of the No. 2 and No. 4 cylinders revealed normal operating and wear signatures.