I think it was Mike Warner who found an old SL70 that was stored for years and had the tank filled with transmission fluid. Once drained and rinsed with gas, the entire fuel system looked perfectly preserved. The inside of the carb looked brand new.
When I stored a K1 that I had for about 2 or 3 years, I drained all the gas and sprayed about half a can of WD40 into the tank and shut the valve. It worked.
ATF seems to be viewed as a magical fluid by some; that's nothing more than urban legend. Motor oil, kerosene, WD40, fogging oil, Kroil, axle grease...among other petroleum distillates would work equally well sealing-out oxygen and thereby preventing rust. The main differences are in ease of cleaning it out, come next riding season. I'll go a step further, downstream of the tank itself, anything but dry storage is a bad idea. The petcock packing is the sole exception; oiling that prior to storage limits shrinkage. Rubber that's been exposed to pump gas will shrink, if allowed to dry out. Fogging oil is, hands-down, the best choice for storage-proofing a gas tank; it'll also be the easiest to clear from the system, having been formulated for the purpose.
Circa 2020, real gasoline - as it existed prior to 2006 - has all but vanished. E10 pulls water from the atmosphere, but it's not the only oxygenate in gasoline. Short of buying gasoline from a specialty supplier such as VP Hydrocarbons, or filing-up at an airport, rust and short shelf life are all but inevitable. Personally, I won't run an unsealed metal tank anymore. (I seal brand-new tanks, prior to installation) As for sealers, POR-15 is the most forgiving and damned tough material, once applied. The downside is that the dark silver color tends to camouflage dirt and gasoline contains more garbage every year. KREEM is a temperamental product; if not applied to a perfectly-prepped surface, it will peel. The white pigment, however, makes it very easy to see how much crap has accumulated in the tank...as well as how thorough your cleaning really is.
