When the slave was trashed on my 2002 1150RT the clutch never made any noise at all, it just slipped under hard acceleration (engine revved but it wasn't going any faster). I'm with Jim, start with the easy and obvious thing first, a slipping belt. That's an easy check on the GS 'cuz there isn't any damned tupperware to remove. I have Hepko-Becker crash bars on mine that have to be loosened but not fully removed, then it's just removal of the plastic cover. If your bike has 80,000+ miles on it that's something you should check anyway. My 2001 1150GS has only 60K on it and still has the original belt (which doesn't squeal and looked fine last time I checked it) but I carry a spare in my kit just in case. The slave cylinder replacement or service really is not a difficult repair on the GS either because access is pretty good, unlike with the RT that was the impetus for this thread. Bleeding the clutch is very quick and easy as well. The last time I had a bike in to the BMW dealer several years ago their shop rate was $79 an hour and I'm sure it's higher now... BTW, the RT is purring like a kitten now, no issues with the clutch after I burned off the bit of hydraulic fluid that made it onto the clutch plate. I love my Beemers; they are remarkably reliable even though they're "old". I spend orders of magnitude more time riding than wrenching on those bikes.