was inbound to Springbank from Indus with only the pilot on board, and was on a left base for Runway 16. The pilot declared an emergency because of a loss of engine power and made a forced landing in a field about 1 1/4 miles north of the runway threshold. The pilot was not injured but the a/c sustained unspecified damages. The pilot later reported to ATC that he believes that the problem was caused by a vapor lock in the fuel system. Tower staff at Springbank indicate this is the second similar occurrence for this a/c. UPDATE The pilot reported that he believes that the engine lost power because of an incorrect setting of the carburetor. The low jet in the Mikuni carburetor had been last set in the cooler temperature of the spring, which would have resulted in an extremely rich setting in the 34 degree C. heat that was present on the day of the accident. He stated that the carburetor should be re-set 3 times a year to compensate for the changes in climatic conditions.