On October 18, 2015 at 0745 central daylight time, a Beechcraft 23, N2339J, was substantially damaged during a forced landing near the Humboldt Municipal Airport (M53) Humboldt, Tennessee. The fight instructor and student pilot were not injured. The airplane was registered to Old School Aircraft, LLC and operated under the provisions of Title 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions were reported near the accident site, and no flight plan was filed.The student pilot arrived to the airplane and conducted his preflight inspection, and confirmed oil and fuel quantities of 6 quarts and 33 gallons respectively. The fuel was strained, and the indications appeared normal. When the flight instructor arrived a short time later, they verified the fuel and oil quantities again. The flight instructor reported that the preflight and engine start were normal. They taxied to the active runway for takeoff. At an altitude of approximately 950 feet above ground level (agl), the engine started to lose power and sounded like it was "missing," according to the student pilot. The engine was generating partial power. The flight instructor took over the controls, checked the fuel, magnetos and applied carburetor heat with no improvement noted. He made a right turn back to the departure airport in order to avoid a residential area immediately north of the airport. He made a series of S-turns to lose altitude and land on runway 22 at M53. Realizing that a highway was immediately off the arrival end of runway 4, and there was a possibility of landing long, he elected to land in a bean field. During landing roll in the field, the nose landing gear sheared off after striking an incline, which resulted in the nose of the airplane striking the ground. Federal Aviation Inspectors examined the airplane after the accident and noted substantial damage to the engine firewall. The airplane was recovered to a storage facility for a more detailed examination. A compression check was performed and all cylinder with the exception of the no. 2 cylinder had compression above 72 psi when a compression tester was used. The no. 2 cylinder would only produce 8 psi of compression. Further examination revealed that carbon deposits were visible on the intake and exhaust valve seats and their respective valve faces. The intake valve would not seat fully due to deposits. The no. 2 cylinder exhaust pipe flange was separated from the cylinder exhaust seat face by about 0.25 in. on the outer left side and the stud was missing the nut and both washers. An examination of the right magneto revealed that it was inoperative. Further disassembly revealed that the permanent magnet breaker end bearing had failed and 6 teeth were missing from the large distributor timing gear. The no. 2 cylinder spark plugs were removed for examination and testing. The top plug tested satisfactorily on a test stand. The bottom plug tested marginally with a weak spark and there were lead deposits found on the electrode. An annual inspection of the airframe and engine was completed on May 15, 2015. The engine and airframe had accumulated 3,082 hours total time and the engine had accumulated 861 hours since the last major overhaul. About 31 hours had accumulated since the last annual inspection on May 15, 2015.