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#312463 - 05/09/10 9:58 pm B Magneto Help - No Spark  
Joined: Oct 2009
Posts: 34
maximini Offline
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maximini  Offline
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I was hoping that some of the experts might help me with a magneto problem. I pulled my B34 out after the winter and could not get it started. Checked it over and found no spark. I tested the HT wire and spark plug and both are fine. I did notice a very small spark between the contact breaker points. The bike worked just fine when put away for the winter.

I'm obviously no Lucas magneto expert! Does anyone have any hints.

Thanks

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#312472 - 05/09/10 10:56 pm Re: B Magneto Help - No Spark [Re: maximini]  
Joined: Feb 2006
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RGSROB Online content
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RGSROB  Online Content
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Posts: 607
Ontario , Canada
Assume you have all ready removed plug cap from HT lead and tried to see if there is a spark directly from the HT lead.follow this logic down to the pick up brush. Also the points can sometimes get a corrosion film on them that acts as an insulator -First try cleaning the points.
Also see if there is any evidence of up and down play at the points end. if so your petaled insulating washers around the mag bearings are goners and must be replaced.
I doubt if it is the condenser in the armature as they usually only decide to quit when hot.

#312838 - 05/11/10 9:11 pm Re: B Magneto Help - No Spark [Re: RGSROB]  
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maximini Offline
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Thanks for the reply Rob. I cleaned the points and set the gap. I notice that I am getting intermittent spark that will jump about a half inch to ground. I removed the pickup, cleaned it and then cleaned the slip ring inside the magneto. I tested the continuity through the pickup and it seems okay. When I kick it I get a pretty strong spark, but then no spark for the next several kicks, then one spark again. Any ideas? I'm stumped.

#312923 - 05/12/10 10:34 am Re: B Magneto Help - No Spark [Re: maximini]  
Joined: Feb 2006
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RGSROB Online content
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RGSROB  Online Content
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Ontario , Canada
sounds like you may have to take the mag off and disassemble.
First check for up and down play as i said previosly.
I have seen quite a few mags recently where the petaled fibre insulating washers are allowing the armature to go to ground

#313046 - 05/12/10 11:47 pm Re: B Magneto Help - No Spark [Re: RGSROB]  
Joined: May 2004
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BSA_WM20 Online content
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Sydney Australia
What type of HT lead are you using ?
This is exactly how graphite ( silicone) car leads behave.
It is essential that you use either a solid copper conductor or even better are the spiral wound leads any thing else will give you grief often intermittantly and drive you crazy


Bike Beesa
Trevor
#313209 - 05/13/10 11:47 pm Re: B Magneto Help - No Spark [Re: BSA_WM20]  
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maximini Offline
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I'm using a HT lead with stranded wire core. I am getting spark with the plug out, but if I put a plug in and create compression, no spark

#313454 - 05/15/10 9:41 am Re: B Magneto Help - No Spark [Re: maximini]  
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Sydney Australia
No spark with new "clean" plugs or no spark with old plugs ?
Modern "fuel" will quickly coat the electrodes and is quite conductive at cylinder pressure.
Pull one out , hold it upside down and "cook" the thread with a strong flame ( oxy ).
If there is a deposit there it will start to burn off and yield a quite yellow ( rich) flame.


Bike Beesa
Trevor
#313568 - 05/16/10 4:56 am Re: B Magneto Help - No Spark [Re: maximini]  
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Bodger Offline
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Bodger  Offline
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Santa Barbara, Cal.
Quote:
if I put a plug in and create compression, no spark


before tearing up the mag any further at least try a new plug...easy and cheaper and quick...then tear the mag down grin

under compression iffy plugs may not do it.

hey, you needed a known good spare, right?

#313648 - 05/16/10 3:13 pm Re: B Magneto Help - No Spark [Re: maximini]  
Joined: Sep 2007
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gREgg-K Online content
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Ottawa, Canada
The fact that you're getting a strong, but intermittent spark makes me think that perhaps your points may not be 100% cleaned up. Could be that you still have a spot of oxide remaining, which will prevent the points from making a good closed contact every once in a while.

I would remove the points and scrape them clean, ensuring there are no pits or oxide remaining. Then, for good measure, coat with a preservative like Electrolube.

.. Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#313969 - 05/18/10 1:02 pm Re: B Magneto Help - No Spark [Re: gREgg-K]  
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maximini Offline
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maximini  Offline
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Thanks to all for all the tips. I changed the points to my spares set, which are brand new and surgically clean and replaced the plug - but the problem persists.

I obtained a spare mag that was recently rebuilt from a friend, but the manual advance/retard control cable threads are stripped. Does anyone know if I can take a spare left-hand end cap(complete with cam face, etc.) and swap it for the stripped right-hand end cap?

I'll use the spare mag until I can get the original refurbished.

#314145 - 05/19/10 9:11 am Re: B Magneto Help - No Spark [Re: maximini]  
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Yes.


Bike Beesa
Trevor

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