Relay Ride '81 KZ750 Ltd Some Signs Of Life Doctor

So, spent the afternoon working on the gf's bike.

Turned out we had the exhaust pipes in the right order in the first place, just a bent rim of a split collar making one pipe sit uneven. Problem solved.
Showed her how to install a new fuel line complete with inline fuel filter. No more fuel leaks. Problem solved.
I had strong signs of life a few weeks ago, then added fresh gas and now the bastard won't start. Nothing at all from the starter. Petcock on Prime, kill switch set to "RUN", clutch in, kickstand up, choke out, quarter tank of gas. I get running lights on the front left only. Hazards work all around, no blinkers on the right hand side. Brake lights, hi and low beams and horn all check out. Everything on the dash lights up as it should, no evil lights. Battery says fully charged on the smart charger, (supposedly a brand new battery from the PO).
I noticed that one lead for the fuel level sensor isn't connected, I'll square that away tonight, would that kill the bike? I'm wondering if I managed to knock something loose for the turn signals installing the battery, could that kill the bike? I'm not the most electrically savvy dude, maybe a fuse, but then why would almost everything light up okay? Maybe a turn signal relay, would that kill the bike?
I'll be spending some quality time with the FSM, but I'm hoping one of the KZ gurus will have an easy fix, maybe one of you guys can armchair diagnose from these symptoms.

If the tires for my bike don't get here in time, the 750 is going to have to be my fallback for the relay, could really use some help here. I already work 2 jobs and I start a US tax law course on Monday, time is not my friend right now. :sick:

Neither of those wires should interfere with the starter circuit.
At the Handlebar push button switch, I'd check for power coming in, then out once the button is pushed. It sounds like you could have a bad Button/ Switch, or a loose connection for it. Also the solenoid itself could have a bad connection. You can easily test the starter and main battery/ connections by jumping the two large posts on the solenoid with a solid metal object like a socket extension. If the battery and cables, then the starter are good the engine will spin over. Make sure its not in gear, or on the center stand if you have one. If this works, then the problem is in the control side, so either the button, or possibly the clutch lock out switch, or solenoid its self.
So do a couple of checks wen you have a chance, then post back.