I de-rusted my tank last summer before letting the project languish until just recently. I had fogged the inside of the tank with WD-40 before I put it up, so it hasn't gone completely to heck. I planned to toss in some hard media and acetone and shake it clean again. I don't think I'll ever get it to shiny metal, but I will get all of the loose stuff out. Should I line it? I have a Caswell liner kit I am on the fence about using because I'm worried about it coming off and causing bigger problems.

My instinct is not to line.

It has worked for some, but I have also read some horror stories.

I think that the original tank tap should have a filter on it and you can add an inline filter - I'd go with that set up, at least to start with.

I agree, run for awhile, if you start to see a lot of crud in the filter then line it. As far as Caswell, it’s my go to and it’s on several of my bikes and no issues, I think it’s the best, IMHO.

Thanks, yeah, my instinct is not to line unless it leaks or is too cruddy. I have a couple filters on hand.

I'll only line a tank if it has pinholes and I can't find a better one.

Like MarkT says. I know you have a metal tank, but for reference if its fiberglass it has to be lined. Modern gas destroys it.
I had a really bad tank on my MX250, swiss cheese and holes all over the bottom. I ended up fiberglassing the bottom outside of the tank and heavly lined the inside. I probably should have found another tank, after finished with all the fiberglass and liner it was very heavy.

I ended up shaking it for 10-15 minutes with a cup of sheet metal screws and acetone inside. After that I did a few cycles of adding a small amount of gas, shake-shake-shake, drain into a jug, repeat until gas comes out clear. During that process the reserve outlet in the petcock clogged once (petcock wasn't installed for the sheet metal screw phase). I think all the loose bits have been chased out now. The main outlet has a filter, and I will run an inline filter as well.

I don't know how I can get it much better. I am tired of messing with fuel and chemicals. Anything further and I think I'll look for someplace to send it away to be re-furbished.

meadeam,
I'm in the Mark T camp of "no liner" unless there are pinholes in tank. If heavy rust I shake w/nuts & bolts as you have done. Then I soak w/Metal Rescue as it removes all rust. This time of year I place tank outdoors as MR works faster in warm temps. MR is approx $25 per gallon at Home Depot or Lowes. I typically use 2 gallons and flip tank later to ensure every crevice is rust free. Not much effort involved since you've completed the nut/bolt shaking. I remove petcock during process to keep crud out, but MR is non-toxic & does not harm paint, rubber, your hands, etc - just the rust.
Best of luck!!

I used red coat after a muratic acid wash and did 2 coats and let it cure for 6 weeks
It seems to be working pretty good after 2 years. Doug