On May 18, 2008, approximately 1845 Pacific daylight time, a Babcock KR-2 experimental homebuilt airplane, N4276Y, sustained substantial damage during a hard landing at Olympia Airport (OLM), Olympia, Washington. The private pilot, the sole occupant, was not injured. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the local, personal flight, which was originating at the time of the accident. No flight plan had been filed. The pilot reported that immediately after takeoff, the engine began "running rough." The engine lost power and he landed straight ahead on the remaining runway. The pilot stated that due to the lack of time and altitude he landed hard. The airplane's left wing was structurally damaged, the firewall was wrinkled, the nose landing gear separated, and the two main landing gear were bent outboard. Postaccident examination of the engine by the pilot revealed that the carburetor's mixture needle had backed out permitting the mixture to become excessively rich, resulting in a loss of power.