On December 18, 1999, at 1210 hours Pacific standard time, a amateur-built experimental Rhea KR-2, N77KR, experienced a loss of engine power and force landed in a parking lot in Moreno Valley, California. The aircraft, owned and operated by the pilot, was substantially damaged during a collision with ground obstructions. The private pilot suffered minor injuries. The personal cross-country flight, conducted under the provisions of 14 CFR Part 91, originated at the Chino, California, airport about 0815, continued to Blythe without landing, and was en route to Riverside. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that he departed Chino with 28 gallons of fuel, which he estimated to be enough for 6 hours of flight with a 3/4-hour reserve. He stated that he flew direct to Blythe, and then flew around the Blythe area approximately 1 hour. He then planned to fly into Riverside to have lunch and refuel before returning to Chino. He stated that his last fuel check at Banning indicated approximately 8 gallons of fuel remaining, with 4 gallons in each wing tank. Approximately 5 miles northeast of March Air Force Base, while at 4,500 feet, the engine quit. The pilot headed for the Air Force base and began emergency landing procedures. He got the engine running again, but it quit after about 30 seconds. About 1 mile out he realized that his glide path was too low to make the airport. He headed for a clearing to his left. Before reaching the clearing, his right wing clipped a tree, bringing him down on top of a building. He then impacted an unoccupied car and came to rest beside it. The car was destroyed. A Federal Aviation Administration (FAA) inspector from the Riverside Flight Standards District Office responded to the accident site. He reported that the wings were removed and tipped on each side to drain the remaining fuel. Approximately 1/2 quart of fuel was drained from the left wing tank, and approximately 10 tablespoons were drained from the right wing tank. The inspector stated that the purolator/filter contained only droplets of fuel. The aircraft appeared to have a capacity of 16 gallons of fuel in each wing tank, with 3 total unusable gallons. According to fuel transaction receipts from the airport, the pilot had purchased 20 gallons of fuel at 0749 hours, and then purchased 2 gallons of fuel at 0753 hours. The pilot/owner reported that following recovery of the wreckage, he discovered a leak in the composite fuel tank. Fuel was soaking into the foam backing. He estimated that 8 to 10 gallons of fuel were lost during the 4-hour flight. He stated that the accident could have been prevented by paying more attention to the fuel tank construction during manufacture of the wing.