I know things... A lot of things.
Join Date: Feb 2015
Motorcycle: GSXR 750 K4
Re: Blown box with ground cables ?
Splices, connections and even wires themselves, have some resistance, which produces heat as currents pass through it. Normally, an electrical installation is designed with this in mind, so that it doesn't cause failures, assuming proper use and maintenance. Things can go wrong for many reasons though: adding electrical bells and whistles, that the system wasn't designed for, can increase the currents and hence heat at connectors and parts of the wiring, as can shorts due to bad maintenance. Exposure to the elements (in combination with design flaws or, much more likely, mods and bad maintenance that increase the exposure of parts of the electrical system - e.g. wires pulled along with their insulations from connectors, missing pieces of fairing, improper routing, etc.) can allow the connectors to collect rust or grime, raising their resistance and hence heat. Once connections start to overheat, the rate of deterioration is accelerated, as they expand or deform.
The solution, is generally to replace the wiring or connectors in question, but given the state of your electrics, perhaps you should consider replacing the whole loom with a used part. Even with bad luck and a small budget, you can probably end up with something that'll be a substantial improvement.
Regarding the specific problems you mention: the earth block is probably just that, a point where all the grounds are spliced together. Overcurrents and shorts, usually lead to the problem you've encountered. More importantly perhaps, having an unfused fuel circuit of all things, can lead to shorts and intense heat near or inside your fuel supply. I assume I don't have to draw you a picture...