Just out cruising on my '90 GS500E and after about 30-45min there was this popping or backfiring and the bike bucked and surged unpredictably. Soon, the engine just cut out all together and shut off. After pulling over and checking the fuel level (fine) and kind of scratching my head it started up just fine, only to repeat above about 20mins later.
I'm puzzled, the bike just got new plugs, wires, and was rejetted (mechanic said 'it runs great now'). Could this be that fuel screen thing?
Thanks in advance for the help...

Possibly the petcock or a pinched vent tube.

Meaning I just need a new petcock or need to switch the selector? I checked the fuel lines and tubes and everything *appears to be in order...
Vent tube...is that the one with the breather filter on/in it?

I assume you tried switching from on to res on fuel petcock. Right? even though tank shows considerable fuel inside you may have run out of gas...just trying to eliminate all possibilities.