On October 3, 2020, about 1600 eastern daylight time, an experimental, amateur-built Quad City Challenger II, N129AY, was substantially damaged when it was involved in an accident near Northfield, New Hampshire. The private pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, he performed a full-stop landing at Laconia Municipal Airport (LCI), Laconia, New Hampshire, and then departed direct to Hawthorne-Feather Airpark (8B1), Hillsboro, New Hampshire, at an altitude of 2,000 ft. About 10 to 15 minutes into the flight, the engine “stopped” suddenly, and the pilot performed a forced landing in a hay field. After landing, the pilot verified that the fuel level was adequate, checked for fuel leaks, and checked the fuel filter and fuel lines for contamination or air bubbles. No anomalies were noted with the fuel system. He then checked the ignition system to see if any spark plugs or spark plug wires came loose. All the wiring from the engine to the bulkhead connectors was in place and not visibly changed from previous inspections. The pilot then rotated the propeller by hand to see if the engine had seized due to lubricating oil starvation, and it spun normally without resistance. He verified that the exhaust was still connected properly and found no anomalies with the engine. The pilot then boarded the airplane, performed the startup procedure, verified that the auxiliary electric fuel pump was operating audibly, and the engine started immediately. He performed a magneto check and verified that both magnetos were functioning properly. The engine ran for about 5 minutes as he verified that the engine temperature and voltages were in the correct range. The pilot taxied to a higher point in the field near a house, where he performed a shutdown and start-up of the engine, rechecking everything before he decided to depart. After completing a run-up, he performed a short-field takeoff procedure, and while climbing through about 100 ft the engine abruptly “shut off.” He completed a forced landing into the field and the airplane sustained damage to the fuselage. An examination of the engine revealed that the No. 1 piston, rings, and cylinder walls were scored and discolored. There was a lack of lubrication within the No. 1 cylinder walls. An analysis of the findings by the engine manufacturer revealed that the engine experienced a piston seizure. Examination of the oil injection system revealed that an oil injection line that supplied oil to the No. 1 cylinder was pinched by the starter motor mounting flange. The pilot recalled that he had performed maintenance in that area about 2 weeks prior and thought that he may have caused the pinched line.