It does... If you needed a tune up because of real dirty plugs, forget it!
I used seafoam on my single cylinder motorcycle and it blasted chunks of carbon all over the white shed door it was next to, and cleaned the plug PRISTINELY. I coud not have done a better job with a q-tip and gasoline or a sandblaster- I was plumb amazed.
Basically I always have at least two cans on hand... I dump some in the motor oil before a change, put a little in the gas tank now and then... Really works its miracles with the combustion chamber though wow.