That's not good news. I feel your pain. Electrics are a worst nightmare. Some can be found and fixed in 20 mins. Other problems (like yours) are totally baffling and the producer of extended forehead veins (and now a sore foot from kicking it
)
Does it run a CDI unit or other fancy black box? Does it have a plug for diagnostics?
I think it's time to break out the test meter, and do EVERY wire in the loom for continuity.
Or, take the loom out of the bike, set fire to it and tell the customer it's shagged beyond repair. Or, ask him if he's insured, and then set fire to the whole machine. (erm, probably not a good idea! - Although tempting)) LOL!
You've done a hell-of-a-lot-of-work to this bike, and probably the bill is going to be more than buying another bike. Is there a cut off point where you say "bugger it...enough is enough"?
It's hard to say where to look now. Apart from the loom, as you've gone down all other routes. There
may be a break in one of the hidden wires (or a wire hidden in the wrapped loom by the headstock etc). Have a look at the exit points in the frame for the loom - are they tight / scuffed / torn?
A wire may appear in good nick at either end, and cutting back connections will reveal good copper - but if the break is say, in the middle for some reason, then the only way to find it is with a meter. Waggling each individual wire is no use!
Leave it a few days and ask yerself what your plans on progression are. Giving up IS an option. Getting a fresh pair of eyes and hands on it is also another option.
Even Einstein got help when he got stuck on stuff! Best of luck.
. happy days.
. but cheers lads for the help.