Howdoyoudo everyone;
Just recently got a '96 500. The previous owner let the bike sit until the tank started leaking. He had the tank coated with the red schmeck by some shop, but wound up taking it back once because their initial application did not stop the leaking. Even after the second coating, it was still leaking so he got pissed and gooped some kind of epoxy material over the exterior of the tank (where it was leaking.) Then he supposedly had the carbs cleaned, but the guy had re-installed them incorrectly. Yes, throttle was a bit funky, but I rode it around town for about two weeks.

Then, had my mechanic re-install carbs, and he mentioned that they were also quite filthy (shortly after they were supposedly cleaned,) so he cleaned them again. Upon leaving his shop, everything seemed awesome, throttle/acceleration was quite normal. Two days after the cleaning, I take the bike on the interstate for the first time. Less than 5 minutes into cruising at 70-75ish mph throttle started vaguely surging/then losing rpms. Then it worsened. Then it got so bad I downshifted to 5th (while taking an exit) but just kind of stalled soon after. It sat for about 20 minutes, then I tried to start it, and it started fine. However, from that point on, it's been running crappy just like it did before the carbs were cleaned.

Mechanic says it needs a new tank. Thoughts? Could it be the traditional petcock issue? I've had my eye on a tank from a 2004... would that work on this bike without any modifications? If the new tank works should I donate the old tank to Buddah? That epoxy might have fowled it...

All input is much appreciated!

the new tank will fit and work without any issues but the seat will just sit up on the tank.  The newer bikes have the seat wrap around the tank and the older style rides up it but many people have put the newer tank on the older models with no problems.