How to remove severe rust in tank ('83 bike rebuild)

[marc]

I'm currently rebuilding a '83 bike that's been sitting 15 years and
left abandoned 5 years under a tree.

Thankyou guys that helped me with the carb cleaning: engine is
currently working and carb works great! Used Srinath's mixture
of gas and acetone, lots of WD40 and Nural/Pattex5000.

Now for the tank: There is gummy residue too, and severe rust in there.
I've heard of mechanical cleaning and chemical cleaning:

- Mechanical cleaning: drop diesel, sand, and all kind of metal bits
(a chain, screws, bolts, nuts, ...) into the tank, and then keep moving it
to remove rust. I've been told to wrap the tank (with all these in it)
in a blanket, and put it into the dryer machine with no heat. Of course,
the most difficult part is the Wife Acceptance Factor of the method.

- Chemical Cleaning: drop oxalic acid into the tank, and let it work for 24h.

Anybody been here before and can give me some advice?

[VTNewb]

When in doubt, a radiator shop will charge you just about 80-100 dollars to acid wash and coat the inside with some sort of polymer or something. THat's what I've always done, because it comes with like a 20 year warentee to not rust again.

[Blueknyt]

ok, no sand, no screws, nuts or bolts, the best thing ive fonud for mechanical scrub is a Dog chain, or swingset chain.  generaly i will remove the petcock and make a plate to put over the petcock hole so i dont hurt the pickup screen with the chain. put about a gallon of diesel(less chance of a spark ignition )  in with the short bit of chain, cap it all off and shake in all directions. kinda like a swirling action, if you use heavy hard items you could dent the tank from inside chiping paint outside.  while doing this take note of any leaks in seams specialy in "bottom edge" areas. pop the cap open hook the chain with a wire coat hanger and remove. put the cap back on, pull the cover plate for the petcock and drain everything out.  repeat acouple times on the rinse cycle witha final rinse of unleaded, 1/4 gal is plenty. back flush the petcock with spray carb cleaner making sure the screen is clean and clear. reinstall the petcock make sure the gasket/Oring is in good shape. at this point you can see about Treating the tank with either Kreem or Por-15 to prevent further rust, OR , buy about 3-4 of the little STONE type fuel filters (lets water pass where the paper ones dont) just to catch any remaining crude shaking loose, change them once aweek for a month (ride it for a tank a week) then you should be good to go for normal filterchanges.