Just for reference: The original ‘79 battery cable is composed with a 3 gauge (0.2294”/5.827mm) tubular braided cable (that’s right – braided, not stranded, wire). The cable is heavily soldered into the two terminals. The cable itself is about 5.5” long, from terminal crimp-to-terminal crimp. The stretched length, between the center of the terminal post holes (including the 90° bend at the solenoid post end) is about 7”. Maybe helpful info if you want to build your own cable.
TimsCBX has a set of nice replacement battery cables: the starter solenoid-to-battery cable and the starter solenoid-to-starter cable. These are both made with what appears to me (without taking the cable apart) to be 4 gauge stranded copper wire. The terminals, anyway, are marked for 4 ga. X ¼" post holes. And best I can measure, 0.210 or so wire diameter, which is consistent with 4 ga. Both have very thick double walled insulation, which makes them a bit stiffer than the stock cables, but doable. The terminals are crimped, without solder.
Apart from the thicker insulation on the battery cable, the only mounting difference is that the Tims battery cable is a skosh shorter than the stock cable, measuring 5.25” of cable, crimp-to-crimp, (vs. 5.5” stock), and the center post hole-to post hole is about 6.75”, vs 7.0” stock. That makes the stretch up from the solenoid to the battery post a bit tight, but it works.
As for the drop in gauge, from 3/0 to 4/0, this is nominal, as the distances of the cable runs are quite short in terms of amps over distance.
Here’s a photo of the stock cable and the replacement side-by-side. If you take a look at my old original cable, where the insulation has been removed, you can see why it might be a good idea to consider replacing these cables. Where the old braided cable has to be bent 90° to mate with the battery, you can see how the braiding has separated over time and shows signs of excess resistance and overheating.
CBX B-cables 2.JPG
And a close-up of that oxidation. FYI the cable was fully insulated all the years it ran on the bike – I just removed the insulation for these pics.
CBX B-cable oxidation.JPG