I have had a Stihl FS85 string trimmer for more than four seasons. I have used it to start the season, trimming out only about 20 lawns. Today, while I was using the trimmer and moving from one bed to another, the trimmer was idling. I felt a bit of a "clunk," an unusual blip in the usual smooth running machine. It was nothing big, but enough for me to notice. I resumed trimming, but quickly noticed it didn't feel/sound quite right. When I went to idle, I realized the trimmer head was still turning. And, when I exercised the throttle, I then understood the head was in sync with the engine. When I finished, I saw the trimmer head stop in sync with the engine. When trying to turn the head, it wouldn't turn. Apparently, the centrifugal clutch has locked up. I continued to use on the next job, and learned it responded just a bit differently. The head is still locked up with the engine, but after turning it off, I was able to wiggle the head so that the clutch was freed. But, I hear a scraping sound in the area of the clutch. It is not a hard sound, but enough to notice. The head isn't totally free, like it should be. What has happened to the clutch? Anybody have this happen to their FS85 (or FC85 edger)? I can still use the machine. It is harder to start because the head is being turned too during startup. The lockup seems to happen quickly upon pulling the starter rope. What is involved in taking it apart? And, how? What parts may be damaged and needing replacing? Help!