The correct manufacturer specified way to clean a foam air filter element is with warm water and dish soap. Using any kind of solvent (or gasoline) will destroy the foam. This is what they taught us in B&S service school many years ago (when MOST of their engines used foam elements) and was the ONLY factory accepted way of cleaning it.
After washing with dish soap and water, squeeze it dry (no need to let the water air dry out of it), saturate with clean motor oil (just pour a little on it, an ounce or two), work the oil in, then squeeze it hard to get the excess motor oil and water out. Whatever water is left over will dry out fairly quickly. If it is not oiled, dirt will go right through it! On two stage air filter elements (foam over paper) don't use very much oil on the foam.
