[WintrSol]

Removing and reinstalling the tank can easily kink the fuel line, just enough that the pump isn't strong enough; something to check. Old fuel lines can partially collapse, too.
There are fine screens at the inlets of the carbs that can get clogged, which are often overlooked.
Also, the petcock has a fine screen above it, in the tank; bad gas and debris can clog it over time, too.

One more thing: check the Voltage at the battery and maybe clean all the connectors, including the connection of heavy black ground cable at the frame. This engine runs on battery power, and a drain to the battery that the generator isn't overcoming the discharge will cause the engine to die. The Voltage with the key off should be 12.6V, or a bit higher, and with the key on, no less than 12.4V, or your battery is getting weak. At idle, depending on your meter, the battery should be over 13V; because of how the charging system works, some meters have problems with the actual measurements, but the Voltage should rise some if you rev the engine. Look for the connector between the stator and rectifier/regulator, the one with three yellow wires; if it is discolored or burnt, your charging system will begin to fail.

 

[WintrSol]

Yeah, the non-California models have a little ball in the vent, to prevent spillage in the event the bike went down. I don't know if it ever worked, but the ball can cause problems if it gets sticky in there. It can be taken apart and cleaned, if that is the problem. Cali models are a different story, of course