Charging system

I am having a problem with my 81 CSR1000. The battery charging circuit is not keeping the battery charged. I have went through most of the old posts, and from what I can see, the charging circuit is working. I get about 12.5 at idle (1000rpm) and about 13.5 to 14 at around 3000rpm. What I have noticed is the wire that comes from the negative terminal of the battery to the case of the engine (Black/yellow) is getting really hot. Hot enough to melt the rubber around the wire connectors. What I am thinking is either the ground is not sufficient, and maybe I need to make another chassis ground, or I have a short somewhere that is dragging voltage to ground. I did check for a voltage difference between the negative terminal to the battery and the chassis, but it was tiny (Less than 1/8 volt). Resistance readings were all showing good continuity to Chassis and negative battery lead. I have thought about buying a new wiring harness to "shotgun" troubleshoot the problem, but I really don't want to dish out the cash for something that might not be the problem.

Here's what I have currently: 1981 CSR1000, big bore kit, dyna ignition, green dyna coils, vetter fairing, and a new high output battery. I have an OEM voltage regulator for the bike that I got off of ebay, and a new aftermarket regulator. New aftermarket regulator does not have the brown sense wire, just a red and black output going to the red/white and black/yellow wires in the plug/wiring harness, and of course the 3 yellow stator inputs. I get about the same readings with both regulators in the circuit. The aftermarket one gives me about .5 volts more than the OEM.

Any suggestions would be appreciated.

Welcome to KZrider!
How's your battery? A motorcycle battery will only last 2 or 3 seasons, normally. If it's low on water, or just old and tired, it will take a charge, but won't hold it for long.
Don't know about your hot ground lead, you'll need some electrical experts to jump in.

The battery cable is clad in rubber insulation. A few years ago, on a desolate road in a light, cold rain, I had the bike quit. Since I am a mechanic and the bike just DIED, I suspected catastrophic electrical failure which generally means a cable came loose or the main fuse blew. I FIRST checked the main fuse... A-OK. Then looked at the battery cables carefully... could see NOTHING wrong.

Got the missus to bring my pickup and trailer and I drug the bike home on a trailer. When I did a continuity test on the battery cable, it had none. HUH? The cable LOOKED A-OK! When I cut open the insulation, I found white powder and NO METAL... not a strand had survived. Darnest thing... but the ends were bright and clean and coated with dielectic grease... I think it was the hot cable (can't recall for sure). Anyway, resistance would go up if the cable was corroding inside the insulation and that would heat up the cable... can't think of anything else. If you had a short to ground, I would suspect that localized problems like fuse-blowing would occur and not the ground heating up.

If the cable tests OK or you replace it and still have problems, test the battery cells. Use a hydrometer; you can get them at any auto parts store... they look like an eyedropper. Get the smallest and use a piece of hose on the tip to draw fluid. If any cell shows some of the balls not floating, the cell has either begun sulfation or is sulfated (DEAD) and you need to replace the battery. Cheap bike batteries can sulfate in a heartbeat.