On August 12, 2000, at 0022 eastern daylight time (edt) a Piper PA-38-112, N2545N, operated by a commercial pilot, sustained substantial damage when it impacted in a corn field during a forced landing near Coopersville, Michigan. Prior to the forced landing, the airplane's engine lost power. Visual meteorological conditions prevailed at the time of the accident. The instructional flight was being conducted under 14 CFR Part 91. No flight plan was on file. The instructor pilot and the dual student reported no injuries. The circuit, cross-country flight originated at Muskegon, Michigan, on August 11, 2000, at 2135. In his written statement the instructor pilot said that he and his student took off from Muskegon, Michigan, flew to Lansing, Michigan for 5 takeoffs and landings, flew to Grand Rapids, Michigan, for 5 takeoffs and landings, and was returning to Muskegon. As the airplane approached Muskegon, the instructor pilot said he told his student to perform a climbing turn and a descending turn. As the student finished the maneuver, "I heard the engine go to idle. I looked at my student thinking he had cut the throttles, and at the same time, he looked at me thinking I was going to say, OK you lost your engine and what would you do?" The instructor pilot said they then realized that the engine had quit. The instructor pilot took control of the airplane and performed the engine restart checklist. The propeller was windmilling, but the engine would not restart. The instructor pilot said he positioned the fuel selector to the right tank and then back to the left tank. The engine still would not restart. The instructor pilot located a field on the ground to land on, shut off everything but the master switch and landed. The instructor pilot said he tried to keep the nose wheel off the ground, but in a couple of seconds, they were stopped. Federal Aviation Administration (FAA) inspectors examined the airplane at the accident site. The airplane rested upright in a cornfield. The nose wheel was broken aft. The lower portion of the firewall was bent aft. One propeller blade was bent aft. The leading edges of both wings showed inward bends. Flight control continuity was established. An examination of the engine's carburetor revealed that a 1/4 inch long and 1/8 inch diameter, angular tab, was totally blocking the hole in the seat. The tab was identified as that used to install a helicoil (threaded insert used to replace stripped out threads when reinstalling a component). Examination of the remaining engine components, engine controls and other airplane systems revealed no anomalies. Airplane maintenance records indicated the carburetor had been reinstalled 300 hours previous to the accident.