On January 6, 2007, about 1200 eastern standard time, a Ryan Aeronautical ST3KR, N56434, registered to and operated by an individual, impacted with a tree during a forced landing following a loss of engine power near Lake Butler, Florida, while on a Title 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airline transport-rated pilot and passenger received minor injuries; the airplane incurred substantial damage. The flight originated from the Flying Tiger Field Airport, Worthington, Florida, earlier that day, about 1150. The pilot stated to the FAA inspector that the engine quit without warning and he had to make an emergency landing. He checked the fuel valve, the carburetor heat, and pumped the throttle but nothing seemed to help. During the landing, he was not sure if he clipped a tree during the approach and was slow to flare out, which they hit the ground hard causing him and the passenger to hit the instrument panel during the stop. The pilot recalls that the propeller was still turning during the impact. The pilot did not have any ideas why it quit. The pilot had been giving several rides prior to the accident flight with no problems. The FAA inspector that conducted the post accident examination of the airplane wreckage stated, during the examination, a short rod that connects the throttle control to the carburetor was discovered lying unattached inside the cowling. It appears that this rod had come loose prior to impact. There were no marks on the rod, the bolt or the bracket that would indicate it was broken during impact. Once this rod is loosen, it would allow the engine to go to idle power.