The noncertificated pilot and his son departed in the unregistered experimental airplane (previously N4114G), on a local personal flight from his private airstrip. During the return flight, they noticed an area of smoke and fire near the pilot's property and proceeded to the area for examination. The pilot descended the airplane to an altitude of about 20 ft above ground level to see what was burning, which diverted the pilot's attention. The pilot "immediately" pulled up to avoid powerlines, "but was 2 seconds late," and the airplane struck the powerlines. The pilot report that there were no mechanical malfunctions or failures of the airplane that would have precluded normal operations.