So I figured out why my tank leaked when the bike was on the side stand....wasn't just old gaskets:



The seat for the Cap assembly gasket was pretty badly corroded. I managed to brush the corrosion out but there's still some pitting as you can see.  Can I just sand it out or how can I ensure a good seal when I put all new gaskets on the cap assembly?  Or some kind of hylomar gasket-treatment?




Also from these images...the assembly itself is in pretty bad shape.  What do I need to do beyond the rebuild kit?  I'm a little worried about the side flange and everything that's flaking off of the assembly. 

That's not as bad as you think it is. A new gasket will take care of the pitting in the tank as long as the remaining surface is flat and smooth. The peeling stuff is paint; a PO had that problem on one of my K100s so he just cleaned it all off and it didn't seem to have any effect on sealing. The final pic is fuel deposits. Show them to a rotary brush in a drill.

Problem solved.