Electrical gremlins, advice needed please...

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Liam Gallacher
Posts: 8
Joined: Fri Jun 15, 2018 5:06 pm
Location: Hampshire UK

Electrical gremlins, advice needed please...

Post by Liam Gallacher »

Hi all,
I am trying to get my 1953 AJS 350 rigid to spark. All I get is a weak spark every fourth kick. I get nothing at he plug and only the occasional spark from end of HT lead against cylinder fins.
I have cleaned the points and the gap is correct as far as I can make out. I have replaced the carbon bush in the HT pick up.
I have a Lucas N1-4 magneto, a Lucas E3 NLI dynamo.
My question is this; As I get an occasional spark can I assume that my dynamo and magneto are working?
Would it help if I fitted a bright spark condenser conversion to magneto?
Would it help if I re-flashed the dynamo?
Any other suggestions?
I have a very basic understanding of electrics so any help in layman's terms please.
As always thanks in advance for any guidance.
Cheers,
Liam.
Mick D
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Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Electrical gremlins, advice needed please...

Post by Mick D »

Hi

First thing to do is to stop considering the dynamo, it has nothing to do with the ignition.

If you haven't already done so, get a new: spark plug, nonsurpressed HT cap and copper conduit HT lead - wire these in and try again, (you're not wasting any money here, all parts should be replaced as a matter of course).
Before replacing them clean the slip ring with a Q tip moistened with petrol to remove any oil or carbon.

While you've got the petrol a Q tip inspect the earth brush and clean the armature where it contacts.

If it still only sparks intermittently check the points for burning which would indicate a breakdown of the magneto capacitor - which is an intricate task to replace, you may think it better to leave this to the professionals and get an Easycap fitted.

If you search the Brightsparks web site there's a wealth of info on there regarding magneto troubleshooting and maintenance - the Library has the Lucas manual for the N1 magneto:

http://brightsparkmagnetos.com/

Regards Mick
Andy51
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Joined: Thu Mar 31, 2005 1:00 am
Location: BERKS UK

Re: Electrical gremlins, advice needed please...

Post by Andy51 »

Hi Liam, you are dealing with 2 completely separate systems. The magneto is a self-contained entity that only supplies sparks to the ignition, i.e. the spark plug. The dynamo's sole purpose is to supply the other electrical accessories - lights, horn and battery. It has no connection to the ignition system and the engine will run happily without the Dynamo. An occasional spark is no guide, you need a regular and reliable spark. Look out there on the wonderful world of the interweb, there's plenty out there on testing magnetos. Have you looked at Christian Gylde's archives.jampot.dk? Most AMC related stuff is on there, including relevant manuals. Hope this helps, Andy
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spookefoote1956
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Location: Wales Innit

Re: Electrical gremlins, advice needed please...

Post by spookefoote1956 »

Sounds like a knackered mag. Either get it fixed or go Electronic.
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Rob Harknett
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Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Electrical gremlins, advice needed please...

Post by Rob Harknett »

Did you remove the points to clean them. You may see something nasty you would not see until points are removed. Like pitted burnt holes this would make points ark so you don't get the spark at the plug or lead. Set the gap right. Recheck brush is good , moves freely, have you put the cable wires through the washer and splayed out so the lead makes good contact. Maybe the special washer was missing and you did not know you should have one. Try a different lead, new plug cap and plug as you progress.. Which you should have spares of. It is often the simple things overlooked that are the problem. The mag is the last thing I would consider. I have never had to do anything to an actual mag. in 64 years. The fact you were unaware the dynamo has nothing to do with mag ignition, tells me you have overlooked something simple. Start at mag. points and lead connections towards the plug until you find the fault.
Liam Gallacher
Posts: 8
Joined: Fri Jun 15, 2018 5:06 pm
Location: Hampshire UK

Re: Electrical gremlins, advice needed please...

Post by Liam Gallacher »

Hi guys, thanks for all of your replies.
Situation update... I got it sparking! I replaced the HT lead, plug, carbon brush, cleaned the slip ring and re -cleaned and re- set the points gap. Result nice blue regular sparks.
Thank you all for your advice and guidance.
Cheers,
Liam.
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