Again... did you try a brand new spark plug yet?... the cylinder walls will not have any carbon build up.... the rings keep them scraped clean... the cylinder head and the exhaust port (of the cylinder) might have carbon build up.... just scrape those off with an old butter knife (don't use anything sharp).... also look inside the exhaust pipe for carbon build up.... and even try putting your mouth to the pipe and blow through it.... air should flow easily thru it.... on the piston skirt and cyl walls you are looking for heavy scuffing and gouging which tells you it has seized in the past.