QuestionHello,
I own a 1975 Honda CB360 that I recently took out of a four year storage and have gotten back in shape. All was going well until recently, a strange problem emerged with the left cylinder spark plug. I went to start the bike one day and noticed that the left cylinder was misfiring. I thought it was really weird because the bike had been running well only a few days earlier. I left it alone for a few days and went to start it again, and at this point, only the right cylinder would start. So, I took out the spark plug and grounded it to the cylinder to look for a spark and there was none. However, if I held the plug a few millimeters away from the engine, it would start sparking. I thought that it might have been a faulty plug, so I went out and bought a new one, and the same thing happened. It started out running just fine, then a few startups later, it was misfiring, and then a few startups after that, it wouldn't start at all. I can't understand what the problem might be. Is it a problem with the coil? Not sure of the reason for this strange problem. Any help or ideas would be greatly appreciated. Thanks!
AnswerRob, first check the ignition timing (point gap at .012-.014", set the point plate to where they open at the F and LF marks correctly). Good idea to check the function of the mechanical spark advance unit behind the point plate too. IT should advance smoothly and retard with spring pressure.
With clean points, gapped correctly, you can then check the resistance of the plug caps... should be in the 5K ohm range. Watch the points when the engine is running. If you see excessive arcing on one side then either the condenser lead is disconnected/loose or the condenser has failed.
Once you have checked out the ignition system and are sure that it is all in order, you can then consider that the carburetor may be fouling the spark plug. If that plug is coming out black after a few minutes of running then it is either getting too much fuel or not enough air.
Bill Silver
