Join Date: Sep 2008
Location: Honolulu, HI, USA
just found this old thread, and as a former owner of two '85 K100RS, my suggestion is to get, read and understand the wiring diagram. It looks like spaghetti at first, but you can isolate and sketch a particular subsystem and study it more clearly.
If the signal wires run through the check relay (forget what it's called exactly) you should know that relay goes bad occasionally. If you study the diagram, you'll be able to apply a couple jumpers that will take care of a bad relay. It's also possible to remove the relay entirely and connect the appropriate wires under the seat for functional turns.