On April 1, 2003, about 1815 eastern standard time, a Piper PA-28R-180, N4952J, registered to and operated by Cirrus Aviation, as a Title 14 CFR part 91 personal flight, made a forced landing in Sarasota, Florida. Visual meteorological conditions prevailed, and no flight plan was filed. The private-rated pilot and one pilot-rated passenger were not injured, and the airplane incurred substantial damage. The flight originated in Sarasota, the same day, about 1725. The pilot stated that he had flown to the practice area and had performed steep turns, slow flight, and steep spirals, and was on his way back to the Sarasota/Bradenton Airport, Sarasota, Florida, at 1,600 feet, when all of a sudden, the airplane's engine ceased operating. He said he saw a road and elected to land on it, but a car later turned onto the road, so he chose to land on a field instead. During the landing rollout the airplane collided with a curb and a sign, incurring damage to the wings. Postaccident examinations of the accident airplane revealed that the left magneto, manufactured by "Bendix", was found to have wear on the aluminum flange in the area where the bottom mount clamp is normally secured. The clamp installed that was intended for a "Slick" manufactured magnetos, and the Bendix magneto had become displaced from its mount. In addition, there was a discontinuity within the engine accessory section. There was the presence of oil in the area of the airframe/engine tubular mount structure, and on the lower left portion of the fuselage. The crankshaft gear bolt was loose and had a flat mark on one of the threads, the lock tab was bent and twisted, and the dowel pin had sheared. The gears within the accessory section of the engine, including the impulse coupling for the left magneto. were undamaged. There was also no damage to the crankshaft gear's teeth, and the center internal bore displayed signatures consistent with there having been a side load. The NTSB Metallurgical Laboratory in Washington, D.C., conducted an examination of the left "Bendix" magneto, the bottom magneto clamp, the dowel pin, the crankshaft gear, the lock tab, the crankshaft, and the crankshaft bolt. The damage noted was consistent with a loss of torque on the crankshaft assembly. The dowel was found to have fatigue fractures emanating from multiple origins at the outer diameter surface, consistent with having been produced by grinding and wear/fretting. Airplane records indicate that on September 1, 1993, the engine had undergone a field overhaul, and had accumulated 1450.35 hours since the overhaul. On October 30, 2002, the engine had undergone maintenance and had both the left and right crankcase halves replaced about 200 hours before the accident.