I noticed my carbs were getting dirty and so I changed the inline filter, but soon realized the tank liner was delaminated. I worked to remove as much as I could manually (see pics) and then dropped a chunk in Acetone to see how long I would need to soak the tank to melt what is unreachable. About 5 days in the Acetone and it had barely even colored the fluid!
Any ideas for getting "whatever this is" out of the tank?
I've had good luck using heavy duty paint stripper. The stuff that requires mineral spirits to neutralize and wash clean. The water rinse paint strippers are much weaker. MEK is also worth a try. Realize that while the chemicals are working there will be an outgassing that occurs so make sure the tank is vented or it will blow up like a balloon and pooch out.
I second the MEK as well. gloves and outside- rotate the tank to keep it on all surfaces, its going to gel up and get nasty. I usually find 3 rounds with washing between, While I do find that adding SS hardware to the tank helps, its also can be PITA to get all of it out.
MEK mixed with screws or chain will do it. Been there, done that. You'll want to setup some sort of strain/seive to reuse the MEK. I think I used two 1 gallon tins for one tank. It wont blow up. Plug the petcock, add about 4 cups and some chain, close tge cap and shake for a few minutes. Strain and repeat.
Do you have any way to heat it? I find solvents work much better hot than cold. I try to do this type of cleaning on hot summer days. I have considered using an aquarium heater in the winter, but haven't tried it yet.
Acetone worked for me. My tank had sat for years with fuel in it and the sealer had delaminated from the tank and settled to the bottom. A few soaks and picking and scraping to get it all. Then a few days soak in apple cider vinegar to remove the rust. A hand full of sharp point screw and a few shakes on the last soak, and then a wd40 rinse to stop flash rust. Good as new.