The pilot was preparing to depart and taxied to the runway, completed a magneto check, and commenced the takeoff. Shortly after takeoff, while initiating a left turn, the airplane’s engine lost power. The pilot reported that he searched for a suitable landing area, while continuing the left turn in an attempt to land on a taxiway. During the forced landing, the airplane contacted a fence and a wooden signpost before it struck the ground and the left main landing gear collapsed. The airplane’s right wing and fuselage were substantially damaged. The pilot reported that there were no preimpact mechanical malfunctions or failures of the airplane that would have precluded normal operation. He further stated that he had inadvertently left the fuel selector in the OFF position and described that because the fuel selector was located behind the cockpit seats, it was awkward to see and access.