I get the same results with NAPA carburetor cleaner. I use it on my Browning Gold shotgun and my AK and FAL pistons. Works like a champ.spsrodco said:I saw your post for SeaFoam and it made me think of something you might want to try. I had to rebuild my Evinrude outboard last summer and I used Evinrude/Johnson carbon cleaner,I can't remember the exact name) to clean the pistons and internals. The stuff was amazing, it literally dissolved the carbon as I watched, even off the face of the pistons. Worth a shot maybe.