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1960 D7 returns after 25+ years
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MickP
Montrose, UK
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April 21, 2017 - 1:32 pm
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Hello all,

I should have been doing a project thread for this bike from when I got it more than a couple of months ago, but I was just too busy and basicly took almost no photos so I have decided it is best just to start from the point it is at now:

It had been off the road for at least 25 years and had its alternator/magneto removed and in bits. I was able to cobble together a charging system and have used a 6v ignition coil rather than the magneto. It is now running well, MOTed, taxed (£0), insured and in use more or less every other day.

BantamHonda.jpg

If I have done it correctly there should be a picture above. (The Honda CG125 is to donate its engine (and possibly other parts) at some point to the D14 frame that is sitting between the two bikes.)

I have a question regarding the alternators on these bikes. Picture below should show two types of coil windings:- one on the left is thiner wire and I estimate that it has about 200 turns on it where as the one on the right is thicker wire with something like about 130 turns. My assumption is that the battery lighting would use two of the 200 turn type and the direct AC lighting would use two of the thicker 130 turn type.

Does anyone know if this correct? I have used three of the thinner type with battery and ignition coil. It seems to be working and not over charging the battery. I am an electrical engineer - amongst other things - so don't worry about being highly technical with explanations.

AltCoils.jpg

Any help, suggestions, encouragement, etc. appreciated.

Michael.

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sunny
Norfolk
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April 21, 2017 - 2:59 pm
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hi  Michael         its  best  you   Identify   the  geny stator    with  its  spec  Number           to  start  with  as    your    bantam  looks  like  a single switch D7   thay   rum  the  headlamp   on  2  coils    and  the  batery   charging  with  1  coil     , &  the  mag coil   as you  know  is  separeted  electricly     sothat   means   3     systems   runing      at   the  same  time      ,,,also      the  same   with  2  switch   bantams       ,,  you   didnt  say  wot  size  wier       in  the  coils   just  from  wot  you  say    its a  none  batery  system   you  have

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MickP
Montrose, UK
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April 21, 2017 - 4:46 pm
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Hi there,

Yes, you are right, it is a single switch Bantam. It was fitted with a very dead battery but no stator/points at all. What I got with it was a box of about half a dozen stators in various states of dismantle. Some had the two main windings, a magneto coil and the small trickle charge winding, others were in bits. There were also three, what looked like, new old stock 200(ish) turn windings which I have used as the others looked a bit roasted. I gave up trying to use the various magnetos after damaging the kick start mechanism and fitted the third winding instead so I could use an ignition coil. There is a hidden switch to switch the ignition on and off.

I removed the trickle charge winding as I don't like the idea of having unmatched windings causing circulating currents and losses/heat (BSA obviously were not bothered) but with the indicators now fitted it might be an idea to re-fit one? - will see how it goes.

It now has all three alternator windings feeding the system, even when the headlight is off, as I have the indicators to supply as well. I always run with the lights on anyway but if the battery were to get a bit low, because of a lot of indicating, then I could just turn the headlight off for a bit. 

There are no numbers on any of the old stator parts but from what I can gather from the wiring harness and battery fitted (and the engine number) it was originally a battery model with magneto ignition. The diameter of the two types of winding wire are (in new money) about 0.45mm and 0.7 mm.

Hope that all makes sense,

Michael.

EDIT: I should have stated that I am running the lights from the battery as the wiring harness and light switch suggested that was the way it was originally (it originally switched the two lighting coils to the rectifier when headlight is selected).

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sunny
Norfolk
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April 21, 2017 - 6:15 pm
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hi  Michael      the   spec  no  is on   the  aly face     platy     below   post  1 &4     ,, staytors  didnot   get numbers  ,  that  were   rated  at  30 Watts   apart  from   the    frist    genymags  units       both  my  single switch bantams   come  up  to about   34 watts   &  have   HT coils   on  the  frame   after   winding   new  coils   to  replace   the   mag coil      ,

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MickP
Montrose, UK
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April 21, 2017 - 9:09 pm
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Hello again, 

I have 4 spare plates, spec numbers: 7156 and 7552 (2 of each type). The 5th is on the Bantam. It is kind of irrelevant anyway as none of them had anything mouted on them.

Of the 4, one has a larger centre hole which did contain a needle roller bearing rather than a bush.

Also, the measurements I made suggested I was getting about 35 watts, which I thought was a bit low but now know that it is not the case - it might struggle to run the indicators!

Michael.

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cocorico
Central France
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April 21, 2017 - 9:23 pm
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I would suggest that as you are starting from scratch, as it were, you convert to a 12V system. In which case you could use your 3 coils to feed a 12V rectifier / regulator to charge the biggest battery you can fit. Then you can still have coil ignition, indicators and better lighting by using LED indicators, tail and brake lights and a small Halogen headlight.

1956 D3 running, lights to sort. 7 other bikes in the Barn. 1950 D1 engine being rebuilt (slowly).

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MickP
Montrose, UK
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April 21, 2017 - 9:31 pm
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Yes, I did consider changing to 12volts, but only after I had ordered 6volt; bulbs, flasher unit and regulator/rectifier (still to be fitted, if there is any point - it will only create more losses). I did order an electronic flasher unit so that i could switch to LED bulbs - just have not had a chance to source any yet.

I will try and get through the summer with it as is but might do a proper 12volt system over the winter - amongst other things.

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sunny
Norfolk
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April 22, 2017 - 11:50 am
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hi  Mick     the  ezyest   way  to  go  12  volt   is  with    classic & motorcycle   mechanics   bantam   conversion       

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MickP
Montrose, UK
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April 23, 2017 - 12:40 pm
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Thank you all for the input, But - can anyone answer my original question?

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sunny
Norfolk
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April 23, 2017 - 5:41 pm
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with   16  difering    spec  no   on  my    55 TYPe   list         i  can  say  yes          " your  spec no s  NOT  on   my     list  "    8  motorcycle  makers  each  with  own  spec  no s   ,,  at lest    2    or  mor   batery  gens   system     have   2 coil  in    SERIES  i  dont    ,    some  spec  no s  cover  2  wiering  looms       ,   just  on  bantams    ,    so   not   an  ezy   ancer    Mick    sorry      to  add  to  that   5   sizes    of  wier 

3   can  be  in  the same   geny    

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mike p5xbx
E-Sussex
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April 23, 2017 - 5:47 pm
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MickP said
Thank you all for the input, But - can anyone answer my original question?  

three permutations of coils fitted are on this page
(although there are two different bottom charging coils)
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D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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mikef
Chatham Kent
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April 28, 2017 - 7:03 pm
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Hi Mick.
      I can understand your confusion. I am trying to figure out what those thinner 200 turn coils are used on.
If you go to the link in the post by "mike p5xbx" you will see the various configurations of coil used.
I was asked a few weeks ago to check out a problem on a twin switched D7 where there was insufficient output from the generator to power the headlamp. The twin switched D7 uses the outside pair of coils in parallel to power the headlight and rearlight when the headlamp switch is turned to the "H" position. The headlight is direct AC. The fault turned out to be the coils. They were both the thinner coils that you described. I changed them for the thicker wired ones and the headlamp worked fine. On a twin switched D7 all of the 3 coils in the generator should be the same.
Referring to the link in the previous post, you will notice that the shape of the centre coil used for battery charging of the single switched D7 is different. I guess because it's output requirement is lower due to the fact that the single switched D7 had magneto ignition and therefore only had to trickle charge the battery and not power an ignition coil.
I still don't know what the coils with the thinner wire are used on, but Sunny did mention a generator with a 30 watt output. Maybe an earlier incarnation of Bantam.
Don't ask me I'm only the technical officer !!!
As always learning and open to suggestion.
Good luck.
              Mike.

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