HELP--My 1978 CB400A Hondamatic Quit

BobM

Help, help. A couple of years ago after riding all day on my 1978 Honda CB400A it just died at a traffic light. A mechanic said he knew what the problem was and installed a kill switch on the side of the headlight bracket. Most of the time it would run fine just like it always had, but occassionally I would have to use the "new" kill switch to kill the engine. At those times even turning the key off would not stop the engine. Last week I parked my bike after riding all day. The next day when I tried to go for a ride, the engine would turn over, but it wouldn't start. No spark at all. A new mechanic checked out the "new" kill switch and said that it should never have been put on. He disconnected it and checked and cleaned the old kill switch and fuses (I had already checked them). He said that the problem is in either the stator or the CDI unit. The Honda dealer charges a little over $700 for these two units. A local salvage yard has them for $120. Does this sound right? Should I replace these two units and see what happens? And, do you know if the stator and CDI unit is the same for the hondamatic as it is for the straight shift? Many thanks for ANY help or suggestions you can offer. Very Happy

Bob

Steve Adams · Posted: Mon Mar 31, 2008 9:23 pm Post subject:

Bob,
I had a similar problem with my CB400A last year before I went to the Cumberland Gap rally when it would die and would not start. One thing is that when I turned off the ignition switch, it would sometimes backfire through the tailpipe. I checked the pickup (Pulse generator) with an oscilloscope and confirmed that it was working properly. I cleaned all the connections and it would start and run for several days or weeks without a problem. Then next time it wouldn't start and had no spark. I found a CDI unit on Ebay that was supposed to be the right one but after I got it turned out to be the wrong one. I later found another one on Ebay that was the correct one. I installed that one and have had no further trouble with it. Look at the manufacture name and part number on the CDI and let me know, the one that I have that was wrong for mine may fit yours. The right one for my CB400A was made by Hitachi.

Steve

BobM · Posted: Mon Mar 31, 2008 9:39 pm Post subject:

Hello, Steve. I sent you an email, but you were out of town! How did you know that the first CDI unit you got was the wrong one? And that the second one was the correct one? By the way, I have the microfiche for all of the parts for the 1978 CB400A if you would ever want to borrow it. It has 64 printable pages. Thanks for the suggestion and offer! I'll let you know.

Bob

Steve Adams · Posted: Mon Mar 31, 2008 9:51 pm Post subject:

I compared the part number and brand from my old one to the photo that the guy took of the second CDI that I bought. The plugs didn't match up to the wiring harness on the first one I bought. I think I paid $40 for the second CDI and the ignition coil came with it too! If your numbers match the one I have that is wrong, you're welcome to it. BTW, I haven't been riding since Sept. 19th, a lady in a minivan tried to occupy the same piece of road I was riding in. Managed to avoid her but messed my leg and knee up pretty bad in the process. I still can't quite bend my knee enough yet to ride. Though I did ride all 3 bikes around the yard very carefully about 3 weeks ago.

Steve

Steve Adams · Posted: Tue Apr 08, 2008 8:22 pm Post subject:

Hey Bob,
Did you ever get the numbers off your CDI?
I got courage up today and climbed on the CB400A, found that my knee will bend enough that I think I can ride it! YEAH!!!!!! Couldn't get it started though, gotta have a new battery. Goona have to wait till the weekend when I can get a new one installed. Look out, if the weather's good this weekend, I'm gonna get my first ride in 6 1/2 months, can't wait!

jeepurz · Posted: Wed Apr 09, 2008 7:02 pm Post subject:

if your needin a manual ive got one on file host, shoot me your email , dont think you have to join to down load it. ive also got some misc cmA parts. also have cb 125 & cb 360 if anyone needs em

macattak · Posted: Thu Apr 10, 2008 6:58 am Post subject:

My guess is it is the CDI, I wouldn't think it was the stator. If it was, the bike would start and run until the battery died. I might be wrong, but I don't believe so. If it turns out to be the stator, try Electrex for a replacement. Not much more than the $120 used one and better quality.

Steve Adams · Posted: Thu Apr 10, 2008 7:24 am Post subject:

It possibly could be the pulse generator that is down close to the stator. It's the thing that looks like a magnetic tape head. As the flywheel turns, a magnet passes over the pickup generating a pulse which is the trigger for the CDI. There are two wires that come out of the left side and run over to the fuse panel to a plug. Carefully unplug that cable and spray the connector with electronic contact cleaner. Sometimes you will get enough corrosion there to cause the pulses to not be strong enough to trigger the CDI.

Steve

sjsartwork · Posted: Mon Sep 08, 2008 12:25 pm Post subject:

does anyone have or know of a schematic for a cdi unit off of cb 400a or cm400a....im interested in rebuilding mine but all the eectrical numbers are missing off capacitors diodes,resistors etc.

please help