On September 3, 1993, about 1844 central daylight time, a Piper PA-12, N2966M, registered to Christopher T. Carter, experienced loss of control during the landing roll at the Greenwood-Leflore Airport, Greenwood, Mississippi, while on a 14 CFR Part 91 instructional flight. Visual meteorological conditions prevailed at the time and no flight plan was filed for the local flight. The airplane was substantially damaged and the certified flight instructor (CFI) and pilot-rated student were not injured. The flight originated about 10 minutes earlier. The CFI who was in the rear seat stated that his son was flying the airplane. At the time of the accident the wind was 10 degrees to the left of the centerline of the runway at 10 knots. His son performed a normal wheel landing and after the tailwheel contacted the runway, the empennage swung to the left. His son applied full left rudder, brake and aileron inputs but the airplane ground looped damaging the left wing. He further stated that he was advised by the owner before he rented the airplane that it was difficult to taxi at low speed which he verified while taxiing the airplane. Examination of the tailwheel assembly by an FAA certificated mechanic revealed that the mounting bolt which secures the tailwheel assembly to the springs then the fuselage was severely worn. Review of the airplane records revealed that the airplane had accumulated about 121 hours since the last 100-hour inspection, which was performed on May 7, 1993.