On July 14, 1995, at 1330 central daylight time, a WZK PZL MIELEC M-18A Dromader, N168RA, operated by a commercial pilot, sustained substantial damage during a forced landing, in a field about 11 miles northwest of Clinton, Missouri, following total loss of engine power. The pilot reported no injuries. The 14 CFR Part 91 positioning flight was operating in visual meteorological conditions. No flight plan was on file. The flight departed Helena, Arkansas, at 1100 with a planned fuel stop at Lees Summit, Missouri. A post-accident examination found the engine capable of normal operation. There was fuel in both the right and left tanks. The pilot stated that he had 2,400 hours experience in this type of airplane, but that this airplane was not equipped exactly the same as others he had flown. This was his first flight in this specific airplane. He stated that the airplane was equipped with low fuel level warning lights which he had not seen before. He stated that in his previous experience, he had noted that one fuel tank might empty before the remaining tank. So, he did not feel that there was anything unusual when the low fuel warning light for the left tank came on about two hours and fifteen minutes into the flight, since sufficient fuel remained in the right tank. About fifteen minutes later the engine experienced a complete loss of power. In this particular airplane was a lever marked "Overflow Fuel Valve - Pull." The pilot stated that he had never seen a similar lever on any other airplanes of this type. He said he thought that it was some sort of dump valve and never thought to pull it when the power loss occurred. He stated that he did not read the aircraft flight manual for this particular airplane prior to departure on the flight. He said that the manual was in the baggage compartment and was not available during the flight. A copy of the "Emergency Procedures" section of the aircraft flight manual is included as an addendum to this report. It describes the use of the "Fuel Overflow Valve," stating that it is to be used to "... prevent ... engine failure in flight," by equalizing the fuel between left and right fuel tanks. A representative of Raven Aircraft Corporation, the importer of this airplane, stated that in most cases the valve described above was either not present (in M-18 models) or was safety wired closed. He stated that it was typical for one tank to empty before the other, but that eventually the other tank would start to feed. He had not experienced the necessity for use of the valve. The pilot's son, who also has imported and assembled this type of airplane, said that a typical problem with the fuel vent system was from a corrosion preventative substance which was applied to preserve the airplane during shipment. He stated that he experienced difficulty in cleaning the substance out of the fuel vent lines; therefore, he had developed a special pressure device used exclusively for the purpose of cleaning out the fuel vent lines. The accident airplane had operated a total time of 1.7 hours prior to its departure on the accident flight since it had been assembled after shipment. The airplane was fueled and then departed on the accident flight, when the engine experienced a total power loss after 2.5 hours of operation. After the initial post accident examination the airplane was disassembled, sold, repaired, reassembled and re-positioned to another location. An attempt was made to determine the state of the fuel vent system. The present owner reported that the vent system appears to be working properly at this time. He has operated the airplane only for repositioning; i.e., about one hour.