barrman some time when you have time take you tank down to you local radiator shop and have them dip it and coat it and it will seal the rust and get rid of the crud had to do this to about 5 or six motorcycle tanks and they worked perfectly ever since just a suggestion us it if ya want but i tell you this much it is alot easier to do that once then to have to clean the filters a bunch of times. btw it unually costs around twenty or thirty bucks for this to be done. deoending on rust and time consumed cleaning it.