Hi there, I have this very cool Sputnik sidecar (not sure of exact year, but likely from the 1980's?). It came mounted onto my 1984 BMW R100RT, but I've decided to keep the bike and sell the sidecar/mount. The sidecar itself is in great condition, with nice functional covers and rubber in good shape. It also includes the DMC mount ($1000 value itself) specific to BMW R100RT (I would imagine it would also work on other BMW R100s?). When I have time I will call DMC to confirm...or you can.
If you were to buy all of this new, it would run you over $6000 plus labor. I am happy to help you mount the sidecar, though I am no expert. My understanding is that this hack was setup by a sidecar specialist dealer in VA, so the current mount/settings should be appropriate for a different R100. It rode well when I used it previously. There are four adjustment points (like tie rods) to dial it in further however. Please let me know if you have any questions and or want more pictures. Also, please note the mount is still on my bike, but I will have it removed this week. I may be willing to split the sidecar and mount. Thank you!