+1 "....from what I can see in the photos, and proper maintenance is everything to the lifespan of these cars. I absolutely would not buy one without a complete verifiable maintenance history, but if you can find one that has been well cared for, then I'd jump on it in a heartbeat."
As i mentioned before, I've had several BMW's. Buying a 'certified' used one or one that's been owned by rich/anal previous owner, but may have ~100K miles on it, is the best way to go. If the previous owner can't document in detail that the big items have been taken care of, these things can be a huge money pit.
F650GS -- sold -- what's next?
“If everything seems under control, you're just not going fast enough.”, Mario Andretti
Indulge. Repent. Repeat.