A saying my Grandpa taught me while demonstrating how to loosen a frozen fastener with a torch . . . . "just cause it ain't red doesn't mean it ain't hot."
Do not completely disassemble the carbs on your vertical twin.
In the dark.
Under an overpass.
In the pissing down rain.
While you're monstered (before Nancy Reagan taught me to just say no).
Until you check for actual fuel in the fuel containment vessel.
Short version, change the petcock setting from RES to ON after fueling.