Motorcycle Repair: 1977 CB750K runs erratic, honda cb750k, keihin carbs

Question
I know this isn't model specific for you but maybe you can steer me in right direction. I have a 1977 Honda CB750K with 4 carbs. I have cleaned them several times but engine still acts like it misfires on at least one cylinder at low speeds. I checked all 4 plug wires with timing light=OK. I checked exhaust temps on each cylinder. At idle all read at or about 250 degrees except for #3 which reads 105. Is it too rich, no fuel, what do you suggest? Any help will be appreciated.

Answer
Sounds like the idle circuit on #3 is still clogged.  Did you take out the plug of #3 and have a look?  This will tell you if it is lean or rich.  My bet will be that it is lean compared to the others.  Since both 2 and 3 fire off the same ignition circuit, you can also change the plug and lead with number 2 and re-check temperatures to completely exclude electrical problems.  Again I think you will need to clean the idle circuit which is a pain on Keihin carbs.

Good luck,  Jan