QuestionMy 1981 Honda CM400C was running like a top, starting with the slightest effort. Then it started taking a tad more effort to start when the engine was cold. I rode it one day, parked it, and it would not start the next morning. Battery fully charged and spinning the starter really good. Plenty of fuel. Pulled a spark plug (new) and could not detect any fire through the spark plug. Someone suggested bad points. The bike seemingly has a coil and CDI. I have not been able to determine whether/whether not there are points. Someone suggested that coils rarely go bad on a bike and thought the handlebar off-on-off switch might be bad. Can the coil be checked? Are there points? The bike seems to have adequate compression. I had noticed of late, sitting at traffic lights a periodic short miss of the engine resembling a droplet of water passing through the fuel system. I was told by a dealer that the coil could not be checked and that I would just have to resort to parts changing till I found the problem. That can become expensive as I would rather replace with new rather than used parts. I do have a Clymer service manual. Your help would be greatly appreciated.
AnswerLOL... I hoped it would be a "Honda" manual... here is the extracts for the ignition system....
Pulse generator test 50-170 ohms Blue/yellow to Green wires
Alternator charging coil measure between all three yellow wires .6 to 1.1 ohms between leads
Ignition coil primary windings .1 to .3 ohms Rebel 450 .55 to .65 ohms all others.
Ignition coil secondary windings 7,200 to 8,800 ohms Rebel 450, 7,400 to 11,100 ohms all others
//////////////////////////////////////////////////////////
I found this just now.... FYI...
http://motoservicemanuals.blogspot.com/2009/03/honda-cb-400-service-manual.html
Wow... Honda 400T ignition woes two nights in a row....
Baseline facts... The system is CDI, does not have points/condenser.
An ignition coil primary windings can be checked with a standard ohm meter, as can the secondary windings. Spark plug caps should read out to 5k ohms.
CDI ignitions are self-powered. The only way to stop the sparks on a running system is to ground it out through the kill switch or the ignition switch.
Pull the wires/plug to the kill switch and check for spark, after you have checked the other components. Hopefully, the Clymer's book has all the specs for your model, as far as troubleshooting the ignition.
Pulse generator coils seem to be an issue with these bikes. They are mounted beneath the flywheel, adjacent to the stator. Disconnect the two wire connector and probe it with the ohm meter for a reading, which will probably be less than 500 ohms. I don't have the exact specs handy.
http://www.cmsnl.com/honda-cm400t-1981-usa_model7287/partslist/E++10.html
Disconnect the ignition switch, jump the starter solenoid posts with a screwdriver to spin the motor over and then look for spark. If you have both kill and ignition switches disconnected and still no spark, then the probable cause could be the CDI module, if you have checked out the pulse generator coils and the ignition coil/spark plug caps.
Spark plug caps fail more often than you might imagine. With a twin lead coil, any open circuit or high resistance will interrupt the spark energy that is circulating between the two spark plugs.
Bill Silver
