Motorcycle Repair: re: cb400a, wiringdiagrams, bike on line

Question
Hi Bill

This is in reference to the 78 cb400a with the cdi problem. I got my hands on a timing light and tested it the way you recommended. During idle it stayed at "FN" and when I put it in gear and reved it up it stayed at "FN" also. I figured I needed a new CDI the problem is the shop I took it to 2 years ago put a cdi for a rebel 450 in the bike (I had a no start problem, it never ran right after that). I found this out (the cdi was for a rebel) when I pulled it and googled the numbers on it. It seems they changed the wirig too. I looked up the cdi for my bike on line and the wiring looked different. So, should I get a rebel 450 cdi, go back to the shop and have them fix it, or get a wiring harness and/or the correct cdi for my bike? This is a tough one I know but I feel I'm sooo close to having a great running bike.

P.s. I looked at my reciept and it said they installed a new stator/alternator/CDi.

Carlos

Answer
I would stay with the CB400T series parts, especially if the plugs don't fit readily. The CDI for an Automatic has way different functions than a 450 Rebel. There was a CM450A which may be similar. Interchanging the automatic and regular CDI units is probably not helpful.

http://oldmanhonda.com/MC/WiringDiagrams/MCwiring.php#class  Look at the CB400A wiring diagram option. I see a "change relay" listed, which may or may not have something to do with advancing the ignition timing.
There is a tie-in between the changing relay and the CDI module, so perhaps the issues are with that part instead, especially if the other parts have been replaced already.

I really haven't had a chance to research or work on the automatic models. Honda does clever things with these bikes, so you really should get a shop manual so you can do any specific tests they recommend.

And put the bike back to stock parts/specs again.

Bill Silver