First off, the fuse that blows is the one labeled "injection" on the fuse box cover (not the one labeled "stop + horn" or "tail + turn") yet the bike runs fine but the brake light does not light up (tail or running light if you will, is on still). So, what's the deal with that? Is my fuse box cover mislabeled?
My guess is that the work experience student who made your loom stuck the stop light/horn wire in the hole at the back of the fuse box where the injection fuse goes, and vice-versa. If you pull the fuse box out, you can check pretty quickly by looking at the wire colours. The wire for the horn and stop light power should be violet with a black stripe. That for the ignition should be red with a black stripe.
Now, this only seems to happen when I take the bike out for a ride...few miles into my ride I'll stop to check the brake light and its no longer working. I can not duplicate the problem in the driveway with either the bike running or not... could this actually help me narrow this problem down? So far its only making it more frustrating.
Fuses blow because of short circuits. Shorts circuits happen because wiring is damaged and the bare wires occasionally touch each other or the frame. This only happens when the bike is running, because you need movement.
My bike has dual HID's which are wired in completely separate of the bar swich/ignition swich, it does not have turn signals or gauges(which I think can eliminate those areas from trouble shooting/looking for short) and I have gone over all the positive batt leads and grounds which are fine and clean as well as both brake switches, plugs and tail light housing, etc.
Check the loom where it goes past the steering tube. On mine, a couple of wires at that point were pinched by a cable tie and part way to cutting through.
