As some of you know, I have had trouble with backfire through the carb. At first I adjusted the valves using the push rod 'spin" method, but today I went through them again using the method described in the tech reference section. Man did I have those rocker nuts too tight!!! My question though is that when I took out the plugs, all but #4 had carbon deposits. This plug must not have been firing. What could be the problem and remedy for one of the cyclinders not firing. It is possible that the plug was bad, but any other ideas or suggestions would be great.