The GS/PD is a solid bike, and so well used that there's a fairly comprehensive list of things that will almost certainly go wrong. It's better to know these things, rather than be suprised (as one would be with a less familiar bike). I'm compiling a list - in order of likeliness (i've had 5 of these in one year, plus the rear shock was replaced by the last owner):

1) battery - the BMW batteries seem to last around 8 years.
2) alternator - especially the rotor - you'll need a spare and an extraction tool.
3) gear-selector return spring - breaks leaving you stuck in the current gear.
4) shaft-drive - check spline wear - this is definitely a design fault.
5) control cables - stuck out in the elements on each side of the engine, many seemingly serious problems are actually just caused by a sticky or frayed cable.
6)subframe cracks, only when overloaded (carry less!)
7)gearbox problems - said to be caused by water getting in, perticularly causing bearings to die and gears to go a missing (lost fifth recently, had a new box put on under warranty).
8) rear-shock - the original is a bit weak, but even expensive ones have been known to break (carry less weight!!!).
9) starter motor - uses a cheaper Veleo model that some people don't like.

Hope that's usefull.

Rob ('93 R100GS/PD)

[This message has been edited by Roboyobo (edited 06 December 2002).]