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Speedo/Horn Rebuild
Speedo/Horn Rebuild
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
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Re: Speedo/Horn Rebuild
- wa1nca
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Re: Speedo/Horn Rebuild
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
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA
Re: Speedo/Horn Rebuild
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
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Re: Speedo/Horn Rebuild
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
- pmtremblay
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Re: Speedo/Horn Rebuild
Thanks for that reference! I have 'fix old Bosch horn' on my list, this is great.schrader7032 wrote: ↑Wed Mar 27, 2024 6:30 amNot a Klaxon, but rebuilding of a Bosch horn was written in the Fall 2010 issue of the Vintage BMW Bulletin.
'66 R27
'22 G310R
- wa1nca
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Re: Speedo/Horn Rebuild
Volume 37, #3schrader7032 wrote: ↑Wed Mar 27, 2024 6:30 amNot a Klaxon, but rebuilding of a Bosch horn was written in the Fall 2010 issue of the Vintage BMW Bulletin.
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
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA