Does anyone know where I can download a BMW workshop manual for a 1989 BMW R80?
This is nice online parts manual. GS oriented, but airheads share lots of parts. http://www.xmission.com/~wendell/GS/ Not exactly what you're looking for, but still a valuable online resource. In conjunction with that, I usually slide by with copies of Haynes, Clymers, and an early '80s BMW manual that I've had for many years. By comparing the same section in a couple of manuals you can usually make decent sense of the job and arrive at trustworthy specs and clearances.