Starting at wiring colors – why are they thus? Well from the early '60s a few companies in the motoring electrical world decided to standardize the cable colors so that we all know where we are when working on motor vehicles. The colors are not there to make it look pretty! They are there so that each color identifies each cable and its job.
The first thought when fixing or rewiring your motorcycle should be to obtain the right color cables. Failure to follow this point won't stop the motorcycle working, but the next time you or the next owner has a problem the job will take far longer and be fraught with unnecessary confusion and puzzlement, to say nothing of frayed tempers and, if you're really unlucky, loads of time off the road trying to sort the problem and maybe expensive smoke!
There are many suppliers of said colored cables out there, along with decent electrical connectors and other widgets for the electrical system, so there is no excuse. A few meters of cable is not expensive. If you are not sure of the colors get a copy of the wiring diagram of you motorcycle and follow it, or get a copy of the Standard Color Chart.
If you really are a 'cheapskate' then get an old loom and use the wires from that, but beware of the 'black death'. What's that? I hear you ask. Well, when you bare off the end of the cable to show the bright shiny copper to which to connect, you find the copper is more 'black' than copper, this is when the cable is tarnished beyond use. If you are stuck by the side of the road with this problem, then scraping with a pocket knife might get you a connection, but if you re repairing at home, get a decent bit or wire for your motorcycle. If you are rewiring your motorcycle and it is supposed to be standard, i.e. most of the electrical parts are in the same position the manufacturer originally put them and you are a bit in awe of this electrical stuff, then and aftermarket look might be the answer. However, be prepared to find several differences to sort out and to spend a fair amount of time poring over the diagram and the motorcycle, to find what goes where and what might need to be modified.
Any significant changes in position or type of electrical fitting will of course need a custom wiring job, which in actual fact can often take less time and be less confusing than the 'standard' look. A old 6v alternator machine changed to 12v will have several less wires. If you can read a map you can follow a wiring diagram.
So you have bought the right color wires and laid all of them on the motorcycle, nominally in the right place and nominally the right length! I often find that the extra 15 centimeters spare I left disappears to not a lot: so even a 30 centimeters isn't too much to leave initially.
Covering! Personally I do not cover the wires with sticky tape because it turns sticky, stiff and messy... and eventually falls off. The manufacturers often use a non-sticky tape which is quite flexible but even tying the ends often don't work too well to secure it.
PBC tubing is the best and easiest bet, perhaps with some self-amalgamating tape on awkward ends and around branchings. Don't make it too tight, especially around the steering head, make sure the wires in the tubing do not inhibit the motorcycle's movement and likewise the motorcycle doesn't hinder the wires. There is stuff called spiral wrap, which is useful for extra protection, but do not rely on it as the only protection, as sharp edges can get through to the wires inside, it shows the wires as well, not good.
Heat shrink tubing is also not the thing to use as a main wire or loom covering because it holds the cables too tight and doesn't allow for fitting of that wire you forgot! It is often thinner than PVC tubing therefore offers less protection – and it is expensive!
Do not bother fitting connectors until you have run all the wires. One job at a time I think is the best way to proceed.
I like to start rewiring a motorcycle from the rear light. Sort the rear mudguard, sort the rear stoplight, maybe pick up wires from the battery area and head for the headlamp. I run all the wires first, then sleeve them, Then return to the back connecting up and ending at the headlamp. It is always a nice time when you sit down on your stool with your coffee and the diagram and sort out those dozen or more wires in the headlamp. Well I think it's a nice time.
Often when fitting bits like rear lights, it is best to stick a battery on the wire that runs up to the light switch to test it before you close the lens. It also helps to sort Stop from Tail (stop is brown, tail is brown/green).