I like where you are goin though - i'm not exactly sure what you mean.
So with the gauge cluster off the bike 7v reg. hooked up i.e. test the gauges? I would put a jumper from the pos. side of the battery to the white/red wire 12v in on the plug and a ground wire to the ground in on the plug ?
That would mimic getting power from the bike and I would get lights presumably, volts, but no fuel and no temp (not hooked up)
am I following? If I have that it should mean there is a problem upstream as in break / disconnect in the wire that supplies power.
all questions in my mind. I am no elec. wizard