Carb cleaner will work okay in some cases. If the material inside the filter is old fuel/oil residue, shellac, for instance.......carb cleaner is not very effective. Acid will break down the substance that is bonded in the tiny chambers within the composite filter much more effectively. If you have a rusty tank from old fuel remnants, acid will make it like new again. Problem is that the acid will remove most, if not all of the zinc as well and after that, the tank can get rusty easier. Old aluminum tanks will become like new again with no problems. You can put in some small crushed rock, or even 1/4 inch nuts, to shake around too. Muriatic acid will remove the rust and deposits, in most cases overnight. Final clean with hot water and baking soda, then clear hot water. Blow with air and/or vacuum then hair dryer. Carb cleaner or lacquer thinner or gasoline other small parts and your good.