The pilot reported that the purpose of the local flight was to put approximately two hours flight time on the engine after some recent maintenance work. The pilot indicated that takeoff and initial climb were normal. After about 50 minutes of flight, the engine hesitated and began to lose power. The pilot noted an initial drop in engine speed of 200 revolutions per minute (rpm). He established a course toward an intermediate airport approximately 6 miles from his present position. His efforts to restore full engine power were not successful, and the engine ultimately lost all power. He executed a forced landing to a corn field, substantially damaging the airplane. A post accident examination did not reveal any reason for the loss of power to the engine.