Well those look pretty good. Dang it! Would have been easy if you'd found this to be your problem. Looking at your spark plugs, #1 and #7 seem to have the most crud. So maybe check the seals in #7 as the others look fine.
I was now years old when I first learned of the Bon Ami procedure here in this forum, although my Dad and I did glaze break the cylinder in a lawn mower with Ajax cleanser, but that was pretty easy to get the head off and back on again! We just wiped the cylinder with it and then spun the crank.
