My Zen has had about 10-15 gallons (atleast) thru it and the cylinder still looked new when I sent it to O'neill for a little work. There are always a few bad lemons from any company..... Zenoah is not know for engines that blow easily. This is either the result of a lemon that mad it out or operator error. In either case, mistakes happen and things don't always work like they are supposed to.