I tried starting the bike today for the first time in weeks after a full rebuild. Nothing, just solenoid click. Checked some connections, still nothing.
I jumped the terminals on the solenoid with the ignition off (should have been on though I think). Realized my mistake and turned the ignition on. Before I jumped the terminals I thought I'd try to start it again for the hell of it and it wa-la, started turned right over.
So what was the likely culprit here? It's working now, but having not discovered what the problem was it seems likely to retun at some point.