On June 15, 2014, about 1110 Pacific daylight time, a Piper 28-180, N4931L, experienced a partial loss of engine power after takeoff from Gansner Field Airport (2O1), Quincy, California. The certified flight instructor and three passengers were uninjured, and the airplane sustained substantial damage. The airplane was registered to a private party and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, and no flight plan was filed. The pilot reported that he took off with 10 degrees of flaps. During the initial climb, the pilot retracted the flaps and the airplane started to lose altitude. He extended flaps again, and the airplane continued to climb, but once he retracted them a second time the airplane descended. The pilot realized the airplane would not climb and elected to make a precautionary landing onto a nearby field. During final approach, the stabilator impacted a fence post, before landing uneventfully. A postaccident examination by a Federal Aviation Administration inspector revealed compression on all four cylinders. The intake system was examined and revealed no restrictions or damaged components. The carburetor float bowl was removed and the fuel inside appeared uncontaminated. A light was shined in the forward exhaust pipe and it appeared to be partially blocked. Examination of the aft exhaust pipe revealed it was also partially blocked. Both the forward and aft mufflers were removed; in both cases, the muffler baffling separated from its mount and covered the exhaust port outlet. Review of the engine maintenance logbook records revealed that the most recent annual inspection was completed on May 15, 2014, at an airframe total time of 4,016.55 hours. The pilot reported that, at the time of the accident, the airplane had accumulated about 3 hours of operation since the annual inspection. The front muffler time in service could not be determined. The aft muffler time in service was 1,359 hours. During the inspection, an exterior inspection of the muffler system was performed; however, the exhaust system inspection recommended by Piper was not performed. The Piper Cherokee Service Manual states in part "…a very thorough inspection of the entire exhaust system including exhaust heater shroud assembly, muffler and muffler baffles, stacks, and all exhaust connections and welds must be accomplished at each 100-hour inspection. The possibility of exhaust system failure increases with use. It is recommended that the system be checked more carefully as the number of hours increase, therefore inspection at the 700 hour period, that the exhaust system has been in use would be more critical than ones in the 100 hour period. The system should also be checked carefully before winter operation when the cabin heat will be in use. NOTE: Piper recommends that all PA-28 airplanes be fitted with a new muffler at or near the 1,000 hour period of which the muffler has been used."