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.

It's possible there wasn't any compression in that cylinder due to the tight valves. Put a new plug in that cylinder and fire it up. After it warms up pull the plug wire off that cylinder and see if the engine slows down/runs rough. If it does, that cylinder is firing now. If it doesn't, check the wire/cap/compression/vacuum leak.

Tom