How to know what horn fits my cm400a?
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Thread: How to know what horn fits my cm400a?

  1. #1
    Senior Member WoundedCyborg's Avatar
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    How to know what horn fits my cm400a?

    My horn stopped working. I have the manual but no luck seeing anything horn related in there. To my knowledge it's just a matter of the horn itself or the wiring. Battery is good, right now mentally prepping for the horn being the problem.
    How do I know what horn will fit my bike? Right now just eyeballing for two prongs for the connection and 6V, anything else more technical to go off of?

    (Right now looking for loudest horn under $50 if anyone knows of any to suggest)
    Last edited by WoundedCyborg; 08-10-2019 at 09:51 PM.
    1980 Hondamatic cm400a "Yoru"- first, my one and only.
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  2. #2
    Senior Member Alan F.'s Avatar
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    Connect a test light to determine if your horn circuit still works, connect horn directly to your battery to determine if your horn still works.

    I was not aware that the CM400A had a 6 volt system.
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    Super Moderator J-T's Avatar
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    It's not. 6v horn should work really good for just a little bit.

    Search for part number 38110-443-621. According to CMS it's common to 98 models.
    Bill H likes this.
    JT
    81 CM400T

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  5. #4
    Senior Member Bill H's Avatar
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    I have had luck taking them apart and cleaning them on other bikes but dont know if you can do that to a cm 400a horn.

    Bill

  6. #5
    Senior Member WoundedCyborg's Avatar
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    Quote Originally Posted by Bill H View Post
    I have had luck taking them apart and cleaning them on other bikes but dont know if you can do that to a cm 400a horn.

    Bill
    you mean you are unsure if an aftermarket horn exists for the cm400a?
    1980 Hondamatic cm400a "Yoru"- first, my one and only.
    The grape of a forum filled with fine wines.

  7. #6
    Senior Member WoundedCyborg's Avatar
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    Quote Originally Posted by J-T View Post
    It's not. 6v horn should work really good for just a little bit.

    Search for part number 38110-443-621. According to CMS it's common to 98 models.
    unsure where i got 6v from. Id rather not get the same horn if it can be helped, something louder if possible. If not louder since I'm assuming the voltage is limiting, at least cheaper than the price of a new honda brand horn. But I'm unsure how to search for a horn that's compatible with my cm400a. That part number seems to get me variations of the stock horn only.
    1980 Hondamatic cm400a "Yoru"- first, my one and only.
    The grape of a forum filled with fine wines.

  8. #7
    Senior Member Bill H's Avatar
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    I once had a free to me Mazda horn that I cut the bell off of and made a bracket to mount it on a cb77. It worked fine and if you didnt look real close it looked good.


    Bill
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  9. #8
    Super Moderator J-T's Avatar
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    Pretty much any "upgrade" will require some degree of fabrication. Most likely as simple as drilling a few holes in a piece of metal and bending it to make stuff fit.

    If you search for "motorcycle horn" you will find many sources, here's just an example:

    https://www.jpcycles.com/motorcycle-horns

    Here's a possible candidate:

    https://www.jpcycles.com/product/360...-low-note-horn

    If the description does not include a decible rating it likely won't make you happy. 90 db is loud enough to require hearing protection over extended periods, likely anything above that could fit your needs.
    JT
    81 CM400T

  10. #9
    Senior Member WoundedCyborg's Avatar
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    Quote Originally Posted by J-T View Post

    https://www.jpcycles.com/product/360...-low-note-horn

    If the description does not include a decible rating it likely won't make you happy. 90 db is loud enough to require hearing protection over extended periods, likely anything above that could fit your needs.
    This horn looks great to me, is this an example of one that will need a custom mounting bracket? Also, I think one of my core questions is voltage, this one is 12V- that's ok for my bike, but a 6V would be bad?
    1980 Hondamatic cm400a "Yoru"- first, my one and only.
    The grape of a forum filled with fine wines.

  11. #10
    Senior Member 80cb400t's Avatar
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    Voltage is how much electrical potential is required to get current to flow, so a 6V horn requires less electrical potential than a 12V horn. This means you can power a 6V horn with a 12V system, although you can probably see it's overkill. It will still work but might do weird stuff like be much higher in pitch or louder or last for less time, it's hard to say. If you're buying one just get a 12V for simplicity.

    Also, making a mounting bracket is quite easy and most aftermarket horns probably will need one. You might need a drill and one of hacksaw/grinder/dremel, and if you really get into it a vice and hammer would be very useful for making bends. I don't have any scrap metal laying around so I just walked around the hardware until I saw something for ~ 1$ that looked like it would work. This is your chance to express your creative side
    Last edited by 80cb400t; 08-12-2019 at 11:28 AM.
    1980 CB400T - 1 running, 1 parts bike
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