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1978 CB400A Hondamatic No Spark Faulty CDI Conversion

43K views 49 replies 17 participants last post by  Bill H 
1978 hondamatic cb400a

Hi all

Just wanted to put this up in case any other 400A owners land in the same boat as I did a few weeks back.

Basically, one sunny afternoon after work my 78 hondamatic refused to start. After taking the plug out and seeing no spark, I checked everything I could think of (sidestand, neutral, kill switch etc) but to no avail.

After getting it back home via pickup truck I did some tests on the CDI, the stator, and the coil as per instructions in the manual and found that my CDI was out of limit on a few. If you ever need to find a CDI for a 1978 CB400A let me tell you they are RARE!!!! After calling around everywhere i could, there was a dealership on the other side of Canada that could get one from japan for about 480$. Not wanting to spend that much i looked at ebay for some used ones. I only found 1 and that was 250 shipped.

But after doing some research I found others who had gone the used part route and had dead on arrival parts. I was directed to CDIMAGICIAN and contacted him. He let me know that he does not make new CDIs for the 400A, but his new 400T CDIs will work as long I replace the stator and flywheel with 400T parts.

So back to ebay I went and as most of you know, 400T parts are much easier to get a hold of then 400A parts!! I was able to pick up a stator and flywheel for 200 bucks plus the 100 for the CDI.

Overall I spent 50 dollars more for 1 new part and 2 used, instead of trying my luck on a risky used part (apparently 400A CDIs are known to break down consistently).

The installation was pretty simple, I had to buy a 10 dollar flywheel puller (bolt threaded for the flywheel that you screw in with an impact and it pulls the flywheel off the stator as it tightens). And just follow the manual.

Few notes on the install:

1) the screws holding the Fixed Pulser on the 400A are much shorter than that of the 400T so I had to swap out 2 of the crankcase cover screws to fit on the new 400T pulser.

2) your colour scheme will be slightly different when joining the wires from the new 400T CDI to the old harness from the 400A. It's simple when you look at it, basically you just match up the wires from the CDI to the ones connecting the coil and stator.

3) there are 4 fewer wires on the 400T CDI then there are on the 400A. Meaning you have to sacrifice the kickstand/neutral cutoffs (400A had safety cutoffs that shut down the engine if you put the kickstand down while in gear,. and also wouldn't let you start the bike if it wasn't in neutral). The wires left over from the "circuit board" near the rectifier (light blue and green/black) and the ones coming out of the kickstand switch (green/white and green/black) need to be taped up and tucked away. Same with left over wires coming out of the harness.

Tried out everything and the bike now fires and idles fine. Will be finishing up the taping and taking it out for a test drive soon with new plugs. Will update then!!
Hi,there.I'm having trouble not getting spark on my78 hondamatic cb400a and I saw what you Would advise here on the forum.I'm just wondering what year of the 400t I should get my parts of, like the flywheel and stator?Also the cdi ignition box?
 
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