I've been working at this for a while. Got my 91 f2 in June 2012. Got it from a salvage yard. It had no lights, gauges, etc... just a running driving motorcycle, with nothin else. Slowly started fixing it. First issue I noticed right away was the starter button on the handle bars doesn't work. After replacing the button assembly and the solenoid, it still doesn't work. So I rigged a button to jump the solenoid, and that's how I start it. Eventually got it to where all I needed was the headlight bulb. When I got the bulb, the bike died within 30 minutes and had to be push started (I had power, but it wouldn't crank). I assumed it was the starter, but it earned perfect the next day. So, I replaced the stator and regulator, not the rectifier though. I also got a new battery. After riding maybe 5 miles, the engine died. Again, still had power, but it wouldn't crank, and this time I couldn't push start it. Got a multimeter hooked up to it after charging the (new) battery, and it read 12.55. Went for a short ride and checked it afterwards, and it read 11.46. Left it overnight, the next morning it still read 11.46. Turned the key and dropped to 10.53, then steadily dropped. When trying to start it, it dropped to 3.10 initially, then barely registered anything (same reading at the starter). Its obvious something is draining the battery when the bike is "on", I just don't know what. It did this with and without the headlight in, so I eliminated that, that apparently just speeds up the process. I'm out of ideas???

 

Ignition is electronic. It needs a minimum voltage to fire properly. When I removed the battery from my f2, it ran horribly and would not rev. In the beginning of your video it looked like the back of the headlight plug was touching one of the fairing supports. Check that area for signs of grounding. I have heard that higher wattage bulbs can overtax the charging system on f2s. Download a manual and trace the circuits from the headlight, starter switch, and the battery to the black box. Something is shorting to ground.