By November 5, 2008

1980 Honda CB400T: Adama opens his one great eye

One of the cool things about my 1980 Honda CB400T is that I bought it to tinker with. I want to learn more about wiring, and do some of the light-duty mechanical work I used to do when I owned a 1974 Jeep CJ5 and a 1974 Volkswagen Super Beetle. I miss being able to change the clutch on my Jeep. Not really, but it was cool that I could do it. Twice.

Anyway, one of the not so cool things about a motorcycle that is almost thirty years old is that some of the technology is lacking. Adama has disc brakes up front, but a drum on the back. The headlamp was also woefully inadequate. The first time I took him out at night I almost shit myself. I should have duct-taped one of my LED flashlights to my helmet for all the good it would do.

I decided to replace the headlamp as soon as possible, but this turned out to be a little more difficult than I expected.

The first thing I did was take the old bulb out. It was a sealed beam bulb, which means it was a lot like a big ass filament bulb you would put in your house. I measured the old bulb — 7″ — and ordered an H4 halogen replacement headlamp from Classic Garage. The lamp arrived quickly. The connectors were the same, which made me happy. I was concerned I would have to get a wiring harness and splice it into the existing wiring. That was the easy part. The rough part was making it fit: the new bulb was too deep to fit in the original headlamp bucket.

I eventually got around to ordering a second lamp and bucket from I bought a plastic bucket because I figured the second bulb wouldn’t fit in the old bucket, either.

The inside of the old bucket looked like this:

That’s a shit-ton of wires. I think that represents the entire electrical system of the CB400T. I had to disconnect them all in order to take the turn signals off and remove the old bucket. I thought ahead and labeled all the wires and where they went. I numbered them, with “A” being one end and “B” denoting the other. I used masking tape and a Sharpie.

It took a long time, but I was glad I did it — especially after I got the old bucket off, put the new one on, and realized the new bucket didn’t fit properly.

I was going to have to use the old bucket. I thought I was screwed for sure, but I held the old bucket up to the new one … and noticed the new one was actually slightly bigger. What the fuck? Looks like I just disconnected all that shit for nothing.

I was very glad that I labeled everything, because the sun was going down and I was frustrated. Reconnecting the taped ends made it very easy. The hard part was folding all the wires in just the right way for me to put the new bulb in. Which just barely, just barely went on. I screwed the bulb into the housing, and Adama opened his one great eye:

The good news is that the new light is much better than the old one. The bad news is that it’s still way below Cylon or Raider. I have some auxiliary lights to put on, but that’s for another project.

Posted in: motorcycling

9 Comments on "1980 Honda CB400T: Adama opens his one great eye"

Trackback | Comments RSS Feed

  1. Starbuck says:

    Good Job!!!!! I like the numbering idea 🙂

  2. erin clare says:

    When you’re done, can i give that to me daughter? 😉

    And if you can’t cite the source of that line then I shall be REALLY disappointed with you.

    Actually, when you’re done can you come help me fix up a vintage BMW bike??

  3. drfaulken says:

    Lo, there do I see my Father.
    Lo, there do I see my Mother.
    And my Sisters, and my Brothers.
    Lo, there do I see the line
    Of my people, back to the beginning.
    They do bid me to take my place among them,
    In the Halls of Valhalla,
    Where the Brave may live forever.

  4. Rick C says:

    Looks good…My wife Has a 1978 CB400TII. Bike is in great shape but like you I need to replace the old bulb. I was going to ask if you had a part number for the bulb you used. I ordered a H4 replacement that didn’t have the same mounts as my old bulb but I didn’t order from the place you mentioned. Anyway if you happen to have a part number that would be great.

  5. Rob says:

    Please tell me you have a part number for that headlight. I just bought myself a 1978 Honda CB400T and I’m not quite sure whether the headlight is out or if the circuits are just bad. But please if you could get a parts number that’d be awesome.

  6. Rick C says:

    Yeah I posted back awhile ago looking for the part number as well but I have never heard back on the part numbers. Would still love to know the part number as well. If I happen to find out the number I will pass it on.

  7. Rick C says:

    Hey thanks for the info. I will be buying one of those today and reusing my old bucket like you did.

  8. Byron says:


    I was wondering if you could give me some help with a set of wires on my 79 cb 400t. Someone had previously installed a fairing on it, and now that I have taken it off, there doesn’t seem to be enough plugs for my wires. What I have right now are 4 wires to plug into, and six that need to be plugged in. I can get all the lights to turn on if I have 4 plugged in, and try and ground out the extra wires on the forks, but nothing flashes and certain ones go out when I put on the turn signals.