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Open contact breaker points #702114
07/18/17 2:17 pm
07/18/17 2:17 pm
Joined: May 2016
Posts: 7
Louisiana, USA
I
IkeIke Offline OP
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IkeIke  Offline OP
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Joined: May 2016
Posts: 7
Louisiana, USA
I'm working on a CB34 GS935 and have a question on whether the points should show a closed circuit when they are open. I'm using a static timing light and it's showing a closed current when the points are open. Is this normal? It has been my experience that the circuit should be broke when the points are open or a piece of insulated material is place between the contacts. I suspect the points are shorted out. The spark plug will fire intermittently when I turn the engine over but will not start. Just a very loud backfire every now and then. The attached photo shows a piece of plastic shrink wrap between the points and the light showing a closed circuit. Any advice? Not sure if the photo will be accessible as I'm not familiar with how to add a picture to this post.


BSA Gold Star Points.JPG[img]http://i61.photobucket.com/albums/h...ar%20Points_zpsqppi0s23.jpg?t=1500300733[/img]

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Re: Open contact breaker points [Re: IkeIke] #702119
07/18/17 3:56 pm
07/18/17 3:56 pm
Joined: Feb 2007
Posts: 488
Ewing. NJ
E
edunham Online content
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edunham  Online Content
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Joined: Feb 2007
Posts: 488
Ewing. NJ
Your experience is probably with a more common coil and points system. I doubt there is nothing wrong with your points. On a magneto, a continuity light across the points will remain on whether the points are open or closed. On my Velo and my Norton (K1F and K2F magnetos), the light will work if you remove the central screw. This is only accurate if there is a sufficiently tight fit on the taper that the position of the points plate won't be disturbed by removing the screw. You must remember to reinstall the screw when you are done-the bike won't fire without it.

Ed from NJ

Re: Open contact breaker points [Re: IkeIke] #702123
07/18/17 4:43 pm
07/18/17 4:43 pm
Joined: Sep 2013
Posts: 1,641
Pacific northwest
Q
quinten Online content
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quinten  Online Content
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Joined: Sep 2013
Posts: 1,641
Pacific northwest
All else being equal ,
You are simply tring to replace the .oo2 gap (cigarette paper) with a multimeter continuity test ?

I have read , probably somewhere on britbike , that removing the center fixing nut will allow a such a test .


Edit .... Opps , what Ed said ... first .

Last edited by quinten; 07/18/17 4:46 pm.
Re: Open contact breaker points [Re: quinten] #702657
07/24/17 7:08 pm
07/24/17 7:08 pm
Joined: May 2016
Posts: 7
Louisiana, USA
I
IkeIke Offline OP
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IkeIke  Offline OP
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Joined: May 2016
Posts: 7
Louisiana, USA
Thanks for the advice. I will try removing the center fixing nut. I that doesn't work, then I'll do the cigarette paper method. I'll keep you posted.

Re: Open contact breaker points [Re: IkeIke] #702658
07/24/17 7:12 pm
07/24/17 7:12 pm
Joined: May 2016
Posts: 7
Louisiana, USA
I
IkeIke Offline OP
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IkeIke  Offline OP
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Joined: May 2016
Posts: 7
Louisiana, USA
I assume the center fixing screw is the one at the opposite end from the individual contact points?

Re: Open contact breaker points [Re: IkeIke] #702664
07/24/17 7:58 pm
07/24/17 7:58 pm
Joined: Aug 2001
Posts: 7,028
scotland
triton thrasher Online content
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triton thrasher  Online Content
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Joined: Aug 2001
Posts: 7,028
scotland
Zero measured resistance across open magneto points is normal. The ohm-meter current is passing through the low tension windings, whoch have very low resistance. If you clip a low voltage battery and buzzer across the points, you might hear the tone change when the points open.


Amateur Loctite enthusiast.
Re: Open contact breaker points [Re: IkeIke] #702666
07/24/17 8:10 pm
07/24/17 8:10 pm
Joined: Aug 2001
Posts: 7,028
scotland
triton thrasher Online content
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triton thrasher  Online Content
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Joined: Aug 2001
Posts: 7,028
scotland
Originally Posted by IkeIke
I assume the center fixing screw is the one at the opposite end from the individual contact points?


What are you on about?

It's the hex head screw in the middle of this lot.

[Linked Image]


Amateur Loctite enthusiast.
Re: Open contact breaker points [Re: IkeIke] #702926
07/26/17 11:49 pm
07/26/17 11:49 pm
Joined: Feb 2014
Posts: 382
Cork Ireland
C
chaterlea25 Offline
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chaterlea25  Offline
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C
Joined: Feb 2014
Posts: 382
Cork Ireland
Hi All,
TT
The MO1 mag has a face cam and the centre screw head is underneath the outer point contact
that has to be removed before accessing the centre screw

Ikelke,
An electronic magneto timer can be bought that detects the exact contact opening point,
several here
https://www.eBay.com/sch/i.html?_fr...S0&_nkw=magneto+timing+&_sacat=0


John

Re: Open contact breaker points [Re: chaterlea25] #703429
07/31/17 9:43 am
07/31/17 9:43 am
Joined: Jan 2013
Posts: 185
Blue Mountains, Sydney Austral...
G
geordie Offline
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geordie  Offline
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Joined: Jan 2013
Posts: 185
Blue Mountains, Sydney Austral...
Anyone know what lurks inside the electronic mag timer? it might be possible to make one


58 goldstar
74 commando
70 Thunderbolt
81 Darmah
Re: Open contact breaker points [Re: geordie] #703448
07/31/17 2:07 pm
07/31/17 2:07 pm
Joined: Mar 2014
Posts: 564
Denver CO
J
Jerry Roy Online content
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Jerry Roy  Online Content
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Joined: Mar 2014
Posts: 564
Denver CO
Originally Posted by geordie
Anyone know what lurks inside the electronic mag timer? it might be possible to make one



BING oh! laughing

http://www.gasenginemagazine.com/Gas-Engines/Building-and-Using-a-Magneto-Timer

http://buzzzboxes.com/

CZ


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