I have been running Enya 4 cycle engines for almost 20 years. They are no super powerhouse engines but will last forever if broken in right. I am puzzled by the "silvery" look to your exhaust. Usually if the back plate is being scored the residue will go through the engine and come out black, with possible metallic chips showing if the gouging is severe. Can you hear or feel any rubbing or scratchy sounds as you turn it over? If so, I would send it back as the previous poster recommended.