On May 17, 2004, at about 1922 mountain daylight time, a Piper J4/E, N37982, registered to and being operated by the pilot as a 14 CFR Part 91 personal flight, experienced an un-commanded reduction of engine power. The pilot initiated a forced landing in a field about one-half of a mile north of Ferndale Airfield, Bigfork, Montana. Although the initial landing was uneventful the rollout resulted in a nose over. The aircraft was substantially damaged and the airline transport pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed and no flight plan had been filed. The flight departed Ferndale, Montana, about one hour prior to the accident. In a telephone conversation and subsequent written statement, the pilot reported that while returning to land at the airport, the engine began to "surge". Carburetor heat was applied with no effect. The pilot continued towards the airport, but was not able to maintain altitude or establish visual contact with the airport due to terrain. The pilot further reported that since he was unable to reach the airport, he turned approximately 180-degrees and initiated a forced landing in a field. During the landing roll the pilot, in an attempt to avoid running into trees, applied the brakes "aggressively" which resulted in a nose over. During a follow-up telephone conversation the pilot reported, "I am convinced the engine quit running because of fuel starvation." He related that the airplane had been "topped" three days earlier and had been flown two hours previous to the day of the accident. On the day of the accident he flew for about an hour. He further revealed that he was aware that the wing tank was empty because he had observed "bubbles" in the fuel sight gauge, which extends out the bottom of the wing tank. The pilot also reported that the airplane was equipped with one 18-gallon wing tank, and a 7-gallon header tank. Post accident examination of the aircraft by maintenance personnel from Discount Aircraft Salvage, found all engine controls to be functioning properly and approximately one tablespoon of fuel was drained from the fuel gascolator. After adding approximately one gallon of fuel to the header tank, the engine was started and ran smoothly with no malfunction or failures noted.