On July 13, 2002, approximately 1820 Pacific daylight time, a Champion 7ECA, N9542S, registered to an individual, recently purchased by a private pilot and being flown by another private pilot accompanied by the purchaser sustained substantial damage during a collision with rocks on a forced landing following a total loss of power approximately eight nautical miles northeast of Ellensburg, Washington. Both pilots were uninjured. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was operated under 14CFR91, and originated from Colfax, Washington, approximately 1630. The pilot conducting the flight (front seat) reported in a telephone interview with the investigator in charge that the second pilot (rear seat owner) had just purchased the aircraft and they had departed Colfax with approximately 20-25 gallons of auto fuel distributed approximately equally between each of the two 19.5 gallon tanks; and that the aircraft's Continental O-200 engine burned approximately 7 gallons per hour average. After about 1 hour and 40 minutes of flight time the engine began to run rough and lose power. The pilot trouble shot the power loss and regained full power after which a climb from about 4,500 feet to about 7,500 feet was executed. About 10 minutes after the first power loss a second power loss occurred. Although the pilot was able to get the engine restarted twice during this power loss, he could not regain full power and eventually he executed a forced landing. The front seat pilot provided no written statement (NTSB Form 6120.1/2) of the accident. Subsequent to the crash the pilot observed that the right wing tank was dry and the left tank had an indeterminate amount of gas. The aircraft was equipped with a single "OFF" - "ON" fuel selector. When in the "ON" position both tanks feed the engine simultaneously. The rear seat pilot (purchaser) reported in a telephone interview with the investigator in charge that he did not check the fuel prior to departure but did convey to the front seat pilot that the aircraft owner had stated that there was about 20 gallons of auto gas aboard. Neither pilot was able to verify from the owner the fuel status. The rear seat pilot did not preflight the aircraft and did not know what the true quantity and distribution of fuel was onboard. After about 20-25 minutes the hangar door was opened and the aircraft was brought outside. The rear seat pilot reported that he assumed that while he was opening the hangar door the front seat pilot was preflighting the aircraft. They departed Colfax and "flew I-90 from Sprague Lake over Moses Lake to the site of the forced landing," a distance of approximately 152 statute miles (refer to CHART I). The rear seat pilot also reported that subsequent to the forced landing he checked the right wing fuel tank low point drain and observed only enough gas to moisten his thumb. A check of the left wing fuel tank low point drain yielded a steady stream of gas. When he returned to the aircraft the following day to begin recovery procedures he was unable to siphon any gas from either tank. He also noted that there was no significant gas observed when the wings were removed from the airframe. The rear seat pilot provided a written statement (NTSB Form 6120.1/2) of the accident (attached). The surface temperature at Ellensburg, Washington, at 1753 on the afternoon of the accident was reported as 82 degrees Fahrenheit and surface winds were reported from 300 degrees magnetic at 24 knots gusting to 32 knots. The surface temperature at Moses Lake, Washington, at 1752 on the afternoon of the accident was reported as 90 degrees Fahrenheit and surface winds were reported from 050 degrees magnetic at 8 knots.