On September 10, 2011, about 1506 central daylight time, an experimental-light sport Quicksilver GT400 airplane, N2590A, conducted a forced landing following an in-flight loss of engine power near Bolingbrook, Illinois. The sport pilot, who was the sole occupant, was not injured and the airplane sustained substantial damage. The airplane was registered to a private individual and was operated by the pilot under the provisions of 14 Code of Federal Regulation Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The flight departed from the Bolingbrook's Clow International Airport (1C5), near Bolingbrook, Illinois, about 1500, and was destined for the Cushing Field Ltd Airport, near Newark, Illinois. The pilot reported that he departed 1C5 at full engine power and climbed to 450 feet above ground level. He then reduced engine power and heard a crackling sound. The pilot stated that the engine “faltered.” He moved the throttle full forward and there was no improvement in engine response. He performed an off field landing. A postaccident detailed examination of the engine and airframe was conducted. The examination noted that the airframe’s main longitudinal structure tube was bent. Examination of the airplane’s fuel system revealed that the primer bulb exhibited a weathered appearance. The primer bulb installation did not contain a bypass fuel line. The primer bulb was removed from its fuel lines and no anomalies were detected when it was manipulated by hand. The fuel lines were reconnected without the primer bulb in place. The engine was started and test run. It was operational during the test run and a reason for the loss of engine power was not found. At 1515, the recorded weather at the Joliet Regional Airport, located about nine miles south of the accident site, was: wind calm; visibility 10 statute miles; sky condition clear; temperature 23 degrees C; dew point 15 degrees C; altimeter 30.02 inches of mercury. The carburetor icing probability chart included in Federal Aviation Administration Special Airworthiness Information Bulletin No. CE-09-35, Carburetor Icing Prevention, indicated that the airplane was operating in an area favorable for the formation of carburetor icing at glide power based on that recorded temperature and dew point. Subsequent to the postaccident wreckage examination, the airplane kit manufacturer was informed that there were no anomalies detected with the primer bulb. However, there was no primer bulb bypass fuel line in the accident airplane and their kit construction documents did not list a primer bulb bypass fuel line recommended by the engine manufacturer for aircraft installations utilizing a primer bulb. As an added safety measure, the kit manufacturer, in part, responded: There is nothing unusual or special about the fuel tank and engine installation on the GT400, so the use of a bypass line in conjunction with a primer would be beneficial and add some redundancy in the event that the primer check valves restrict flow, etc. We will add some supplementary guidance material to the manuals to recommend a configuration that includes a bypass line and put out a bulletin. An Accredited Representative from the Austrian Civil Aviation Safety Investigation Authority reviewed this accident report. He indicated that the Authority concurs with the kit manufacturer’s addition of the primer bulb bypass supplementary guidance in accordance with the engine manufacturer’s recommendation.