I have yet to try to restore a vintage bike without coming across a rusted tank. Some are beyond salvage, but some aren't that bad, it just depends. It depends on whether someone left it out in the weather for years, or kept it in a garage or barn with half a tank of premix in it. No matter what you do the first step is to fill the tank 1/3 full of nuts, bolts, nails or washers with a little solvent (or soap and water) and sit down and shake. And shake, then shake more. Then 3 hours later it's ready for Kreem. Well I hate Kreem, it seems to always fall off. I would prefer to just get all the rust out and then let my premix keep it clean but that is not always an easy proposition. At least not till now. Where I work we have several sizes of vibrator polishers the smallest of which cleans my 9 mm brass up shiny and new for reloading. So this got me to thinking and well just look at the pictures.
I used 5 minute epoxy to glue this 1/2" thick aluminum plate to the bottom of the tank.
This tank will need to be painted so I don't care if I have to scrape the epoxy residue off once I heat the plate with a propane torch and it falls right off.
Of course I don't totally trust 5 minute epoxy, so a little duct tape is in order.
I guess you can see the trick now, the vibrator under the tank.
I simply bolted the tank on the stud that clamps the lid onto the vibrator.
Here is a view of the special rocks used in this size vibrator but almost anything would work like pea gravel or nuts and washers.
I let this tank vibrate for about 90 minutes and I must say it looks brand new in side. It may have taken me a half hour to get those last 3 rocks out of the tank, but after that and a solvent bath it looks brand spanking new.