On Tuesday, August 3, 1993, at 0930 eastern daylight time, a Gera Nieuport II, N44030, a homebuilt airplane, registered to and piloted by Max V. Gera, sustained substantial damage during a forced landing in a field in Somerville, New Jersey. The pilot received minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was being conducted under 14 CFR 91. The pilot stated that this was the third flight in this airplane. On each flight, including this one, after takeoff, the cylinder head temperature (CHT) climbed in excess of 500 degrees F. After the two previous flights, the pilot had modified the engine cowling, in order to provide improved cooling. On this flight, the pre-takeoff checks were performed without any unusual indications. The engine RPM reached 2300. Once airborne, the CHT began to rise and exceeded 500 degrees F, and the engine RPM's decreased to approximately 1600. The pilot stated that he was unable to maintain altitude and airspeed, and he landed the airplane in a field. Mr. Rodney A. Bourey, Airworthiness Inspector for the Federal Aviation Administration, examined the airplane. This examination revealed no discrepancies of the engine or the airframe.