I have a Custom Chopper with a 1992 1340evo, my voltage regulator rectifier came unplugged from the starter. I plugged it back in and it started and ran. The next day, I started the bike and it ran for a few seconds and then lost all electrical power and shut off.
So, my guess is that it ran purely from the battery, without receiving any charge from the stator, and then it stopped when the battery was depleted. This can be confirmed from measuring the battery voltage with a multimeter, with the engine running - you should see around 14v if it's being recharged, and from 12 to 13v if it's running on its own. For that you'll have to start your bike again - you probably will need to recharge your battery for that, or maybe just wait a couple hours - sometimes batteries will recover a little bit after some time, enough for starting the bike.