Any idea what would cause this?

Posted by barelycompetent on
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Any-idea-what-would-cause-this-tp4039735.html

Im sure this has been discussed before but its just come up with me.  My 1,2 and 3 exhaust headers become hot when the bike warms up, but the #4 is just warm and can still be touched.  I pulled the spark plugs, I have iridium plugs in my bike, a 1981 cb750k, and 1,2 and 3 were good, you could still see the white iridium part, on #4 it was black and had oil on it.  In the pic the #4 plug is on the left and the #1 is on the right.  Is it possible I have three cylinders running lean and one rich?  The bike starts and seems to run just fine, other then my high idle lol.  Any input on what to check, or how to remedy this situation is greatly appreciated.  Thanks in advance.