The wiring on older bikes is the Devils spaghetti.As Kawboy says, it’s most likely something simple. I had similar problems with my old Z1000j, it turned out it was a single black wire that had come loose.
Thanks, LareNuminen, I will definitely check them out.
McZee, that's an awesome chart! I haven't laughed that hard in awhile. I too had a J model. I loved that bike and wish I hadn't sold it. I was seduced in to doing so by a near pristine '79 MGB roadster.