Sounds like maybe the petcock was off, it stopped getting fuel, or needed more choke?
They usually need the choke on for a while when it's cooler. I go full choke, slide the lever as the rpm comes up and keep the rpm about 1500-2000 until it starts warming up. If I just turn the choke off, it will die shortly and won't start without choking again.
It can take a few cranks to get the fuel going if it sits a few days.
Sometimes after warmed up then parked 20 minutes, I use full choke to fire it quicker, and as soon as it fires the turn choke off .
I have whole tank off the bike and I have long gas lines on the carbs. I use a small tank with a small nozzle that I fill the gas lines with. Then refill as I need. I am going to rig a bottle with a t in the lines to give constant gas to the carbs but I haven't done that yet.