On June 23, 2023, at about 1000 central daylight time, an unregistered Quad City Challenger II airplane was substantially damaged when it was involved in an accident near Cedar Creek, Missouri. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that the airplane had not been flown since October 2021. On the day before the accident, he drained the fuel and replaced it with new fuel, replaced the fuel filter, and checked all fluid levels and lines. On the day of the accident the pilot flew the airplane for about 20 minutes and then landed to pick up the passenger. After takeoff, he flew for about 10 minutes when the engine sputtered, and the engine performance degraded despite his advancing the throttle. The pilot executed a forced landing to a field, impacted trees, and substantially damaged the wings and fuselage. A postaccident examination of the airplane and engine were performed at the pilot’s residence. During the examination, it was noted that the exterior of the engine was covered in oil, particularly concentrated near the power take-off (PTO) piston and cylinder head. A blue oil coating was also evident on the side of the aircraft consistent with the color of the injected oil. The oil injection lines appeared to be in pristine, unused condition and were lacking securing clamps. However, a piece of old, brittle oil injection line was discovered near the oil injection pump, and the fuel, primer, and vent lines were also found in an aged and hardened state. The magneto piston, cylinder, and combustion chamber appeared to be in normal condition with no anomalies found. However, the PTO piston exhibited vertical scoring, and metal transfer marks were observed on the corresponding locations of the cylinder wall. The transfer of metal was indicative of a piston seizure. According to the pilot, when he purchased the airplane in 2008, there were no maintenance records available. In 2009, he installed new fuel lines and fuel pump, rebuilt the carburetor, replaced the spark plugs, safety wires, brake lines, wheel innertubes, checked cylinder compressions, drained old fuel, and replaced the trim tab. There was no maintenance performed after 2009 other than annual fuel filter replacement. According to the Rotax maintenance manual for the 582 UL engine, all hoses of the lubrication system must be replaced every 5 years.