Howard
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« on: 22.11. 2011 18:47 » |
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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.
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cyclobutch
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« Reply #1 on: 22.11. 2011 20:52 » |
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Either that or just keep it looking pretty and fit a bulb horn at MOT time.
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'58 Iron Head Flash Bitza
'59 James Commodore
'67 Bantam D10/D14
'80 V50 II
'89 XLH1200
'06 G11 Griso
'07 ZRX1200R
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trevinoz
Newcastle, N.S.W. Australia.
Forum Oracle
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« Reply #2 on: 22.11. 2011 21:47 » |
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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.
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Howard
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« Reply #3 on: 23.11. 2011 19:44 » |
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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
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nagrod
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1960 BSA Super Rocket
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« Reply #4 on: 29.11. 2011 14:08 » |
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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 |
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'Never again. But that's what I said the last time.'
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trevinoz
Newcastle, N.S.W. Australia.
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« Reply #5 on: 29.11. 2011 21:11 » |
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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.
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A7Paul
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« Reply #6 on: 01.12. 2011 22:36 » |
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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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trevinoz
Newcastle, N.S.W. Australia.
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« Reply #7 on: 02.12. 2011 00:47 » |
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Hi Paul,
Yes, it is a pain in the arse 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.
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mike667
A's best friend
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« Reply #8 on: 03.12. 2011 04:44 » |
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that blows
sorry could n't help it
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A7Paul
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« Reply #9 on: 07.12. 2011 14:07 » |
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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
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BearKat
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« Reply #10 on: 12.01. 2012 13:47 » |
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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.
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Ex RASC "DON R"1958/60,(BSA M20 /MATCHLESS G3)
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Sav
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Webmaster VMCC Men of Kent
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« Reply #11 on: 13.01. 2012 09:55 » |
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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. |
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1961 A10SR, spent a fortune at SRM
1961 A7SS, finally the right green
December 2011. New addition 1937 Empire Star, twin port, high pipes.
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