Recently bought a 96 Virago 535 with the exact same problem. The carbs had already been cleaned and you could tell work had been done to the bike. We started at the fuel tank(belly tank under the seat) when we emptied it the fuel was orange, which was caused by rust. Called Yamaha and was told a new tank would cost 1k! Not gonna happen here! We went to our local auto parts store. We bought some acid and soaked the tank (read and make sure you get the right acid). Cleaned it out well, dried the tank WELL(harder than you think), then we bought some stuff to line the tank. We put a second coat in the tank to make sure we had it protected from future rust. Filled her up with a high octane fuel, added some seafoam, and she runs great! All for under $50! We have taken her out on the road and she runs perfect! This may not be your problem, but if your carbs have been worked on already try checking the fuel in that belly tank. If it is orange....your baby is starving! Good luck and we hope this helps others!!!