Looks like your Coke is getting warm
That's a project that will be worth it. We use battery terminal cleaner on the connectors and wash them out with non chlorinated brake cleaner. Then dry them out with the air nozzle, and fill the female half with dielectric grease before reconnecting. The brass parts come out nice, shiny and clean.
We've had great success with this method and have only replaced 2 wiring harnesses in the two dozen bikes we've resurrected. Many of them started out looking like your bike. This 75' Honda CB 400-4 was as bad as your bike before we got to work.