The pilot of a Piper J3C-50 stated that after completing a preflight inspection, during startup of the airplane, he noticed that the engine was running rough. He made an attempt to clear up the rough running engine by conducting high-speed taxis. He then decided to fly it in the traffic pattern as a safety check. During takeoff, at an altitude of 50 feet above the runway, the engine stopped producing power. The pilot turned the airplane in an attempt to return to the private landing strip, and stalled into terrain. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that dirt and debris was found in the fuel lines. Further examination of maintenance records revealed that the airplane's most recent annual inspection was completed about 5 years prior to the accident. Additionally, the airplane was operating on automobile gasoline, and there was no supplemental type certificate issued by the FAA for the accident airplane's use of automobile gasoline.