Without any testing, anyone here would just be totally guessing.
My total guess, would be to test the fuel pump for pressure (50psi) and volume. The factory unit is a solid piece but it doesn't like sitting for long periods as these bikes sometimes do
You can find a replacement of the same WALBO brand that fits a 2003 V-6 Mustang (IIRC) for about $35 if you are the do it yourself kind of person. Lots of threads here on it, use the "advanced search" its much better than the regular search
The service manual has the procedure spelled out and you can find a free version at Buellmods.com or Buelltooth.com. A good cheat is to hang the rear of the bike from the rafters or an A-frame ladder to remove the rear shock and let the swing arm hang for clearance. That way you don't even pull the rear wheel off