On August 22, 2001, at 1205 hours Pacific daylight time, a Cessna 150M, N63405, nosed over during a forced landing following a loss of engine power after takeoff at French Valley Airport, Murrietta, California. The flight instructor and student pilot were not injured, and the airplane was substantially damaged. Visual meteorological conditions prevailed for the instructional flight operated by American Valet Air under 14 CFR Part 91. The airplane departed French Valley at 1200 for the local flight, and no flight plan was filed. According to the operator, who inspected the airplane and interviewed the instructor, the airplane was topped off with 13.4 gallons of aviation gasoline and placed in the maintenance shop just prior to the flight. The airplane received new tires and was released from the shop. No other maintenance was performed. The airplane departed at 1200 with full fuel tanks, which was 22.5 gallons of useable fuel. The instructor had stated that shortly after takeoff, about 1,000 feet, there was a "popping" sound from the engine followed by a loss of engine power. He repositioned the mixture and throttle controls, but with no effect. He stated that he pitched the airplane to attain best glide speed and initiated a forced landing procedure. The airplane landed in rough terrain and nosed over. The engine was examined at a recovery yard. The mixture, throttle, and carburetor heat control cables were connected through the firewall to their respective positions on the engine, and worked appropriately when activated. The crankshaft was rotated. Mechanical continuity was established for the valve train and the accessory drive section. The accessory section gears were clean and undamaged. The right and left magnetos provided spark when activated. Thumb compressions were established for all cylinders. The carburetor was removed and inspected. The throttle valve was in place, as was the one piece venturi. The carburetor float was of metal construction. Fuel was noted when the accelerator pump was activated. An examination of the left muffler revealed that the aft end was missing. The entire back portion of the muffler was open. There was evidence of sooting and discoloration of the firewall directly behind the left muffler. The fuel input line leading from the gascolator to the carburetor was positioned between the aft end of the left muffler and the firewall. It was approximately 3 inches away from the open end of the muffler. The fuel line was wrapped in heat shield material, which also exhibited sooting and discoloration. There was a small amount of fuel in the line when it was removed from the carburetor.