A "ring out" check of every single wire for continuity end to end and an isolation check on those wires from ground is common practice in aircraft wiring where a single wire lighting up from a short can take out a week's worth of work, or some VERY expensive equipment.
Once a satisfactory continuity and isolation check is performed, I'd advise on any "new" wiring job to pull all of your fuses and then connect an ammeter between the ground lead and ground and make sure you don't have a draw. Install fuses one at a time and watch the meter. A bike that is "off" should not draw any amperage from the battery at all. In this manner, if a particular fuse installation creates a draw you have isolated the problem to that part of the circuit right off the bat. This should not occur if the previous checks were good, but those are not a guarantee. As we say in the aircraft business, we have all day to get it right and no time to do it over, so do it right!
It would seem your starter circuit is bridged, and downstream of, or at the starter relay. Relay could be stuck, or a wiring error.
