1984 Honda Shadow VT700 Taillight/All other rear lights out.

I recently bought a Honda Shadow, and it needs some work but otherwise runs fine. It backfires when I decelerate, and the rubber mounts for the directionals have dry rotted and they all hang down. But my main problem that I'm concerned about is the electrical problems. The brake light won't work at first, then it will for a minute or two, then it won't for the rest of the ride. The tail light itself won't work, nor will the rear directionals. The tachometer is the same way as the brake light, works for a little bit, but then it stays at 0-1 the rest of the time. I replaced the bulb on the tail light to no avail. Oh, and the licence plate light won't work either. I've checked the wires and they all seem fine. I'm scratching my head on this one. Any suggestions?