On June 2, 1998, at 1250 central daylight time, a Cessna 150 airplane, N6486T, was substantially damaged during a forced landing following a partial loss of engine power near Mentone, Texas. The student pilot, sole occupant of the airplane, was not injured. The airplane was owned and operated by the student pilot under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local instructional flight for which a flight plan was not filed. The flight originated from the Lukins Flying Service airstrip near Pecos, Texas, at approximately 1230. The student pilot reported to the FAA inspector that the itinerary for his solo cross country flight included stops at Mentone and Wink, and a return flight to Pecos. While in cruise flight, the engine began to run rough and the engine RPM dropped to somewhere around 1,200 to 1,500 RPM. After completing his emergency procedures, the pilot elected to execute a precautionary landing on the service road to an operating oil pump, located approximately 2 miles away. During the precautionary landing on the narrow domed road, with the flaps fully extended, the pilot lost control of the airplane. The pilot added that the right main landing gear tire dug into the sand. The right main landing gear collapsed rearward after striking a large rock. Subsequently, the right wing impacted the ground. Examination of the airplane by the FAA inspector confirmed that the right wing, the fuselage, and the landing gear attaching point for the right main gear, sustained structural damage. The reason for the reported rough running engine could not be determined; however, the pilot suspected vapor lock. The engine could not be started at the accident site due to a dead battery. According to maintenance records provided by the FAA inspector, the 1960 model airplane had been modified on June 15, 1996, when a 150 horsepower Lycoming O-320-E3D engine was installed to replace the stock 100 horsepower Continental engine. The modification, performed under STC SA4795SW, also featured a larger propeller and the addition of an STOL kit. According to FAA medical records, the student pilot had accumulated a total of 85 hours at the time of his last medical examination on February 11, 1997. His total time at the time of the accident was 107 hours.