Author Topic: Horn Not Working  (Read 2000 times)

Offline Howard

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Horn Not Working
« on: 22.11. 2011 17:47 »
The standard horn (Lucas I think) on my `51 A7 does not work.I bought the bike as a basket case and am now up to the stage of fitting the horn. I took it apart, cleaned it out but no go. Is there any thing that I should look at in particular ? I want to keep the original horn so need to get it going.

Online cyclobutch

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Re: Horn Not Working
« Reply #1 on: 22.11. 2011 19:52 »
Either that or just keep it looking pretty and fit a bulb horn at MOT time.

Various, including ...
'58 Iron Head Flash Bitza


Online trevinoz

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Re: Horn Not Working
« Reply #2 on: 22.11. 2011 20:47 »
Howard,                 
             If you have the original Altette from 1951, it is the worst type of all Altettes to get working. Especially if you don't have a clue how to go about it.
The first thing to do is clean the points and ensure that the resistance across them is as close to 0 as possible.
Check the coil resistance, should be less than 0.6 ohms for 6V.
Next, assemble and loosen the pushrod locknut and back off the pushrod.
Set up the horn on a bracket held in a vice and set up a dial indicator bearing against the centre of the diaphragm.
Apply voltage to horn and read movement.
The movement has to be set to around 0.010" by shimming with paper gaskets under the diaphragm.
Note that there must be an audible "click" as the armature contacts the pole with 0.010" movement.
If you get the movement right without the "click", the horn will sound weak.
Usually the correct movement without the "click" is caused by too much shimming.
After you have got this right, adjust the pushrod in the armature until the horn sounds right.
A front and back picture of your horn will enable me to positively identify which type you have.
If you were in Australia, I could have done it for you.
Good luck!
                      Trev.

Offline Howard

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Re: Horn Not Working
« Reply #3 on: 23.11. 2011 18:44 »
Hey Trev, sounds real techo for what should be a basic item, thanks for the info, I will give it a try however. regards Howard

Offline nagrod

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Re: Horn Not Working
« Reply #4 on: 29.11. 2011 13:08 »
you may want to check out this site   http://www.taffthehorns.com/     I bought parts for mine from him and he is a great guy to deal with and knows more about these things than I ever want to! I got mine to go from completely useless to working perfectly on the bench but barely bleating on the bike. Gotta work on getting a better ground across the steering head I think. Next spring!!

Just as a side note, does anyone know how these things respond to a 12 volt system?

Rick D
'Never again. But that's what I said the last time.'


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Re: Horn Not Working
« Reply #5 on: 29.11. 2011 20:11 »
Rick,
         The 6V horn works on 12V but the points may need a bit of adjustment, I have found.
Sounds a lot louder!
Obviously you would not hold it on for extended periods or you pay the price!

  Trev.

Offline A7Paul

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Re: Horn Not Working
« Reply #6 on: 01.12. 2011 21:36 »
Hi Howard and Trev,
Have been reading this exchange with great interest as my '48 A7 has a really poor horn volume.  I have taken the horn apart and followed Trev's tuning method.  I have now removed all the gaskets from behind the diaphragm and I still have more than 25thou movement.  Isn't it a long winded effort adjusting the throw of the centre plunger! In desperation I have put a washer behind the diaphragm and on the centre piece and am getting a better note, but I have difficulty centralising the assembly. Is it possible that my diaphragm is too deep/wrong and from where could I get a replacement? 
Paul

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Re: Horn Not Working
« Reply #7 on: 01.12. 2011 23:47 »
Hi Paul,
              Yes, it is a pain in the idiot setting some of them.
Have you got your diaphragm right way up?
If so, you could try carefully bending the sides until you get somewhere close.
Make sure that it is straight when you are finished bending.
The '48 horn should have a point adjusting screw on the back so it is a little easier to set than the '49-'53 types.

Trev.

Offline mike667

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Re: Horn Not Working
« Reply #8 on: 03.12. 2011 03:44 »
that blows

 sorry could n't help it

Offline A7Paul

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Re: Horn Not Working
« Reply #9 on: 07.12. 2011 13:07 »
Thanks for the advice and comments.  My horn must be a later version as it has no adjustment on the back.  I have had some success with flattening the diaphragm and that with a thin washer under the centre piece has certainly improved the volume and tone of the horn. Thanks again for your advice.
Paul

Offline BearKat

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Re: Horn Not Working
« Reply #10 on: 12.01. 2012 12:47 »
contact Taff the horn for a price!, he does a total refurb and you will be a happy piggy,i promise.He is a master.
Ex RASC "DON R"1958/60,(BSA M20 /MATCHLESS G3)

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Re: Horn Not Working
« Reply #11 on: 13.01. 2012 08:55 »
contact Taff the horn for a price!, he does a total refurb and you will be a happy piggy,i promise.He is a master.

Agree with this I have had two Altettes done by Taff the horn, superb! he does like a chat as well if you phone him!!

Sav.
1961 A10SR, spent a fortune at SRM
1961 A7SS, finally the right green
2011 New addition 1937 Empire Star, twin port, high pipes. Turned out to be the most unreliable bike I have handled.
2017 finally found the liner/barrel were flexing and causing all the overheating/nipping up. Early B33 barrel fitted and it's reliable at last!