In my effort to sort out a no-start issue, I've emptied the fuel tank on my 1987 K75S. Sloshed water to clean things up a bit. I'll do a rinse with acetone. I'm then planning to use Red-Kote to seal things up and prevent potential future leaks (no leaks now). Right now, the inside of the tank looks really good. I don't see any of the varnish that others have shown. There was some relatively minor debris but nothing major, IMO. Thanks for any insight/advice.
+1 to the Mighty Gryphon.
After reading your post again, my advice is to
cancel this procedure. If your fuel tank is clean as you've described, if its various vents and ports are clear and if there is no sign of paint beginning to blister along the lower seams of the tank, it isn't the source of your no-start issue but might become one if you don't diligently follow manufacturer's instructions or interpret them in an unintended way.
The fuel tank will stay clean if it has fresh fuel run through it often. It will stay clean if it is stored with conditioned fuel—corn or no corn fuel hasn't mattered to my bike, but it's special :Rabia: —for approximately six months or less. For longer periods, store the tank empty with good air circulation, or empty and well-sealed.
If you intend to proceed in your quest for tank immortality, be certain all ports are sealed.
This post shows a small hole in what the post's author refers to as a burrito of the roof of the tank. If your bike has one of those, be sure it's sealed.