Gas tank cleaning on a 50 year old motorcycle.
I used white vinegar 5%
First wash out tank with some dish soap.
Then using 1/4 of a gallon at a time keep changing the rust colored vinegar.
I rotated tank both directions and forward and reverse.
This was a very bad tank to clean. As I was cleaning aquarium rocks started coming out?
I’m guessing someone use them years ago trying to remove rust?