Topic: CM 400A No spark

[steve]

I have a CM 400A with no spark.  2 experienced bike mechanics have given up on it.  I have checked the stator, kick stand switch, neutral switch, kill switch and replaced the CDI.  Does anybody have any suggestions or experience with a similar issue?

[calj737]

Older CDI boxes are not immune to issues. First thing to verify is the presence of 12v at the coil. Attached is the stock wiring diagram:
http://www.cmsnl.com/classic-honda-fansite/honda_wiring_diagrams/CM400A.jpg

The Kickstand switch should create a "GROUND" for the CDI, so you can bypass that by running a jumper from Green/White to a good known chassis GROUND.

Does the NEUTRAL light show on the dash? Can you provide some other, more detailed symptoms? Some history on the bike and year, perhaps?

[scottly]

Have you verified the correct resistance of the pulse generator pick-up coil? It should be a separate pair of wires associated with the stator; maybe white and blue? The resistance is typically around 500 ohms for most CDI type ignitions, but check the specs for your specific model. Have you measured both the primary and secondary ignition coil resistances? Again, refer to the specs for your specific model. BTW, don't expect to measure 12v at the coil with a CDI....

[steve]

Thanks, I am going through with your suggestions and report back.

[steve]

What power goes from the CDI to the coil if it is not 12V?

[scottly]

Upon being triggered by the pulse generator, the CDI discharges a capacitor into the coil, producing a brief, but powerful pulse of voltage. This brief pulse can only be observed with an oscilloscope. An inductive ignition, like points or Dyna etc, has a constant 12v applied to one side of the coil, which can be easily checked with a simple meter.

[strynboen]

dont think the cm 400 have a cdi ignision..but just a "normal" pick up...vho graunds the coil via a transistor trigged. ground konneltion..just like the cbx and cb 900..and other 1980 bikes

[steve]

It finally is fixed.  Even though the Stator tested fine, I pulled it and had it rebuilt by Ricks Electric.  Works great now.  Thanks everyone1