Speedo/Horn Rebuild

[Slash2]

Anyone ever take a stab at rebuilding these themselves?

I’ve torn a non-op horn down, cleaned it up internally and familiarized myself with the design and how it all goes together but I can’t say that I’ve effectively “fixed” one yet. Before I did anything I hooked it up to a 6v battery with a couple jumper wires and saw zero sparks when I touched the negative wire to the ground. I then tore it down almost completely, cleaned all the parts thoroughly and reassembled. Now I hear a very faint tone and see some weak sparking when I connect power. I haven’t installed the horn in the bike as I’m just bench testing. I tried turning the adjustment knob in/out but no real change was observed in tone. Is there anything written on this unit and how to restore it? Tips or suggestions?

I also have a few old speedos that are non-op and before I send them to some $500 a pop repair shop, I’d like to have a go myself. Surely they’re not a Rolex in there and I’ve got nothing to lose. Does anyone have any resources on rebuilding the speedo?

Thanks!

[Darryl.Richman]

The horn only sounds in a narrow band along the adjusting bolt. Keep track of where the bolt was set originally, then try it for each half turn in and then out.

[wa1nca]

Is it a Bosch horn and what model number

The placement of the curved washer and order of the other spacer parts are very important
I may have your model and will get some pictures if it matches mine

[Slash2]

The horns I’m working on are the French made Klaxon variety indicative of the /2 era.

Should these sound on the bench when connected to a 6v battery or am I missing something? Does the center rear stud need to be grounded as well?

[schrader7032]

Not a Klaxon, but rebuilding of a Bosch horn was written in the Fall 2010 issue of the Vintage BMW Bulletin.

[pmtremblay]

Not a Klaxon, but rebuilding of a Bosch horn was written in the Fall 2010 issue of the Vintage BMW Bulletin.

Thanks for that reference! I have 'fix old Bosch horn' on my list, this is great.

[wa1nca]

Not a Klaxon, but rebuilding of a Bosch horn was written in the Fall 2010 issue of the Vintage BMW Bulletin.

Volume 37, #3

The horns I’m working on are the French made Klaxon variety indicative of the /2 era.

Should these sound on the bench when connected to a 6v battery or am I missing something? Does the center rear stud need to be grounded as well?

Yes, best way to test and adjust to eliminate any wiring/switch problems
The center stud is only for mounting the horn, Only the 2 wires, battery + and _ to power the horn, polarity does not matter.

Note:
The Bosch and Klaxon both have several different working voltages (6-36 volts) and they look similar
Google your model # if not noted on the horn body

You also may have dirty contacts on the spring loaded electromagnet switch and need to be cleaned, should be close to 0 ohms

Also try 12 volts will not damage the horn
Still am using my Bosch 6 volt horn on a 12 volt upgrade