Magneto ignition on Speed 20 SA

The magneto on my Speed 20  SA had just undergone a full repair in the UK and worked perfectly bringing the car over to the continent and driving around here until  some malfunction occured in that the engine would slowly die down but no misfiring or similar. Switching  to distributor the engine ran smoothly again. Restarting some time later the magneto worked again for a while but on a 25 km drive it started to die down again only intermittantly firing the engin until it died down completely but the engin  again ran smoothly on distributor. Since then the magneto did not revive at all. Would any one have an explanation of what went wrong? (coils and condensator were new according to invoices). Thanks for any advice. Posted by Joachim Epperlein 10/08/2012 13:07:57

For many years (previous owner and me) my Speed 25 ran only on coil. Switching to magneto, engine immediately died. Finally, in 2008, I removed the magneto coil and sent it to Adrian Gorvin in UK who rewound. Since re-installing, it has worked perfectly.  That's all I can add.  Have you checked all connections within the distributor and to magneto coil are tight? Could possibly be a loose connection. Good luck! Posted by johnlayzell 11/08/2012 16:24:54

Joachim, Before having an expensive rebuild of the magneto, try changing the condenser.  This is very easy on the BTH CED.6 magneto. You just take the top off and there it is right in front of you.  I bought one from Maplins for £1.99 and it completely restored my magneto.  You may have to muck about with a soldering iron depending on what terminals you find when you open it up.  The correct size of condenser (capacitor) is 0.2 or 0.3 microfarads.  The precise value does not seem to be important, but it should be rated at at least 600 volt. Over a distance of about 100 miles my car began to run badly and then would not start easily. It gradually got worse until it conked out completely, and as I don't have dual ignition the RAC brought me home.  Since fitting the new capacitor I have had no trouble. This may not be the problem in your case, but it's worth trying as it costs almost nothing and is extremely satisfying if it works. All the best, Dudley Posted by Dudley Smith 11/08/2012 23:00:51

If the windings have been re-done,it is most likely to be the condenser that is faulty. For some stupid reason magneto overhaulers do not 'pressurise' the magneto/comdenser under the heat of working conditions; a bench test of one hour, not on a physically hot engine, will not show the fault.These condensers are inclined to fail when warm/hot and quite often begin to work again when cooled down until the motor re-warms. The condenser is located under the top alloy cover of the magneto; if you go in there, and it is a rather ancient flat-looking piece of kit with two wires, it may be the original....... I use a modern condenser and fit it externally with its wires leading through two drillings to the inside connections. This way I can try a substitute if it is suspect without a mag strip down.. Posted by Nickalvis 22/08/2012 20:58:44

just returned from the Cardiff IAD plus some 2850kms trip in my Speed 25 some days ago which was a very enjoyable experience. Thank you all for your advice on the Speed 20 magneto. I have been in touch with Adrian Gorvin since and he advised to send the magneto to him for diagnosis when the car is laid up for  winter. As the magneto repair should still be under guarantee the pain might not be so bad after all. Keep you posted once we know what caused the trouble.  Yours for longer bonnets and best regards Joachim Epperlein Posted by Joachim Epperlein 28/09/2012 13:40:53

The magneto returned home some weeks ago and put back worked perfectly though the car was not taken out yet due to weather. Adrian Gorvin mentioned the fault was due to a bakelite part that was broken and caused short circuits to mass. Probably something very difficult to find unless you are a magneto magician. Hope this will last for longer now. Cheers Joachim Posted by jofrey 11/04/2013 20:33:49