Today I figured out why my instrument cluster on my '85 100RS has always cut out intermittently, particularly when turning the forks sharply. It was replaced (before I got the bike) with a cluster that is marked "9/90" on the back. Apparently BMW changed the electrical connector sometime between '85 and '90- the cluster has round pins, but the plugs on the bike have recesses for rectangular pins. The way that the plugs are clamped into the housing is different, too.
I can't think of a reliable way to adapt from the round pins to rectangular, so I'm looking for a working, good condition cluster with the rectangular electrical pins.
Thanks,
Andy