I'm working on tooling up to make new battery cables for pretty much any machine. Right now 6 gauge wire only, but my 16 ton crimper can do some very large sized wires, 6 gauge is 2nd to the smallest die of the set lol.
I'm also upgrading the fuse holder to a water proof designed one, also uses the more modern mini fuses so should be really easy to find replacement fuses if one ever blows.
Here's the positive battery cable to starter solenoid wire I made for an 84 atc200es.
I've also started making a kit for an ATC250SX, waiting on the crimper for crimping the larger fuse housing terminals for 14 gauge wire to finish it up (this one actually is going on my 250sx). Don't mind the mud on the machine, it's a true rider and Michigan gets plenty of mud/rain to make things nice and dirty lol.
Some quick specs on the parts used.
Marine grade battery cable (high stand count, tinned strands) - 6 gauge
Delphi Mini Fuse holder
Smaller wire is high temp fuel injector grade wiring, way over kill for this area of the machine.
Marine grade adhesive heat shrink (dual walled and sealing type)
Just about everything is USA sourced except the bullet terminal that goes to the red wire on the harness.
I used 6 gauge wire because of the better support for the terminals/lugs, OEM appears to be 8 or 10 gauge. It won't make much of a difference besides lower voltage drop through the wire, so the starter should spin slightly faster.
Anyone interested in some sets? I'd have to run the numbers per machine, but it's looking like it will be around $50 for both battery cables and the starter cable. I also can rewire a newer Honda solenoid if your old one isn't aging well. I'm also looking into wire end caps to cover up the starter, solenoid, and positive battery ends, those will have to cost extra if you want them. OEM might be able to be swapped over.
I do have very limited supplies since I'm not sure what kind of interest this will have. Here's a pic of 100ft of wire and the battery lugs.