I am not an expert in electrical wiring, but I have replaced some of my wiring with 18ga multi stranded copper wire. On some wiring that I thought carried a heavier load I went with 16 ga.
I may have screwed up but I have no problems so far after 3 years. I am sure there is some formula that lets you calculate the wire size depending on what the load on the wire is, but I don't know.
Edit: I did a search on Google for "wire size for motorcycle" and one of the sites here will help.
webmaster10.com/ldr/formulas.htm
Electrical Wire Size
These are MINIMUM size, larger gauge wire (smaller number) is preferred
Up to 10 amps 16 gauge
Up to 20 amps 14 gauge
Up to 30 amps 12 gauge
Another link:
www.rbeelectronics.com/wtable.htm
and another:
www.powerstream.com/Wire_Size.htm
It seems 18 and 16 will be fine for most stuff. The battery cables positive and ground should be about 6 gauge. You need to look at what each wire will carry as a load, and figure out what you need. I think if everything was 16 and 14 ga it would work fine, maybe even be overkill, but I would trust it for anything. If you are powering an accessory, like a big horn, or electric vests, lot's of lights, then the wire size may change.
