On a side note, would "Demon-Clean" work to clean-up oil & carbon deposits on a lawn mower SPARK PLUG?
Sure...spark plugs are cheap, but I hate to do another ring job on the mower.
Art:
Demon Clean will cut carbon. I have a couple motorcycle shops that buy it to do exactly that. Now, for a spark plug, it would probably just be easier (and less expensive) to buy a new plug. If you need to clean the combustion chamber, piston and ring groove, Demon Clean is the answer.
In reply to the person that mentions a striper, that stuff will not cut or chemically remove carbon in the combustion chambers. Watch out for the brass parts also (some sleeves, bushings, con rod bushings, etc...), it may not play well with brass.