Vintage BMW Motorcycle Owners

I have a steel tank that is from one of my other bikes that was coated with an unknown liner by PO 15 years ago or so. After sitting half empty over winter (my bad) bad rust and gunk. I tried white vinegar for 3 days followed by muriatic acid for an hour or so and neutralized with baking soda and a good flush. Did a good job on the bare metal but the old liner is still there and pealing and appears to have rust beneath it. Any advise on a home method for removing the old liner. Wish I knew what it is but alas not. Thanks in advance.

Typically, the way to remove the older liner is to use a number of nuts/bolts/screws along with some dish soap and water. Then shake the tank in all directions and get the hardware into the corners. Every so often, I'd flush the tank with water, retrieve the hardware and maybe try it again. Inspect the insides to see how the process is going.

Set it out in some direct sunlight or under a heat lamp (not to hot) for a while and get it dried out as much as you can, it might take a day or two. A combination of a home made scrapping tool and high pressure compressed air will knock a lot of the loose stuff free. I go a little further and swish around some M.E.K. and let it sit for a while before rinsing.

Stay away from the muriatic acid stuff (might be to late) as it might be bad for the brazing/welds that secure the fuel spigots and lid.

If your not concerned about the paint job a good radiator shop can clean it up but it will probably remove the outside paint on it.

I just read that another person used a gallon of acetone to loosen it from the tank and pulled it out in big pieces using a pair of long hemostats. But it will also attack the paint.

I’ve used acetone or methyl ethyl ketone MEK. Both very poisonous and flammable.. be careful. Length of chain works well as the internal abrasive. Nuts and bolts or screws also work, but you have to count them before and after.