your charging system may not be putting a charge back into the battery. Put a charger on the battery to bring up the voltage, record that number. Let the bike sit without riding for a couple of days, if you can, and measure voltage at the battery terminals again. Record that number. Did it drop a lot from just sitting? Ride the bike and measure the voltage when you get home. Should be the same or very nearly the same before and after the ride.
get a multimeter with amps (milli amps) and connect the probes between battery positive terminal and the positive leads (completing the circuit with the leads disconnected from the battery) and with the ignition off it will give you the current flowing. don't turn the ignition on, the pump and lights will blow the multimeter fuse on the ma setting.
6ma will kill a battery. remove fuses or unplug stuff until you find what makes the current draw go away, then go looking deeper. the voltage reg is connected via the maxi fuse, altho i don't know that a 93 has a maxi fuse. mine isn't complete, but i can't see one offhand. it must have. manual says it does, a charging system fuse of some sort anyway. maybe it's the stupid fusable link on the rh side of the headlight subframe.
Check for wiring worn through from rubbing the frame. It was my regulator wire, but it could be any of them after 26 years of rubbing. I cut all the zip ties and checked the whole harness. It doesn’t take long.