Maggy fix.

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john.whiting
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Maggy fix.

Postby john.whiting » Sun Mar 11, 2018 3:59 am

Hello all.....I need to repair a couple of maggys (BTHs) and a Lucas on old motors,and Im looking into simply rewinding a primary on the armature,using either the existing points or solid state,and a small jap bike coil for secondary......any capacitior ,if required will be external...Theoretically this is the same idea as the old Lucas "energy transfer magneto",famously fitted to the ISDT bikes .....Is this idea available as a modified armature from a supplier?...Needless to say,by using an auxilliary flywheel with a couple of magnets set in it,I can use a $20 mower ignition system.,but that would be cheating?

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paul.jameson
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Re: Maggy fix.

Postby paul.jameson » Sun Mar 11, 2018 9:16 pm

Check that the existing capacitor in the magneto is disconnected. If it is duff (which it probably is) and remains connected, you will still get the engine warm misfiring characteristic of a duff capacitor despite fitting a good new external capacitor.
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john.whiting
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Re: Maggy fix.

Postby john.whiting » Sun Mar 11, 2018 11:48 pm

Paul,Im planning to rebuild the maggys from bits,with a purpose wound primary only on the armature.Instead of experimenting ,I am hoping to get a few details from someone who knows of a conversion that works.For instance ,turns and gauge of primary,whether a solid state breaker inside will work,etc.....One of the motors is/was unused ex army,but the BTH maggy coil has still failed from moisture /decomposition....The advice locally is to dump the motors and sell the maggys on ebay.

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Eero.Korhonen
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Re: Maggy fix.

Postby Eero.Korhonen » Mon Mar 12, 2018 6:49 am

Well that was not a good advice.
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Re: Maggy fix.

Postby nevhunter » Mon Mar 12, 2018 8:34 am

John I think something like what you propose was used on the later speedway JAP's. The "magneto" provides a low tension current only and the coil is near the spark plug with a short HT lead.. There is no slip ring involved with high voltage at all. Some two strokes did the same even back in the 60's. . Nev

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paul.jameson
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Re: Maggy fix.

Postby paul.jameson » Mon Mar 12, 2018 10:35 pm

I have seen this conversion done, very successfully, but the only description was "I wound a whacking great primary..." The resulting sparks were huge. My starting point would be the same gauge wire as the original magneto primary but perhaps up to a quarter more turns to beef things up a bit.
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Re: Maggy fix.

Postby nevhunter » Mon Mar 12, 2018 11:22 pm

It's better done with a rotating permanent magnet. (rather than the coil rotating) That eliminates the connections problem.. The more "juice" from it the better the result. You run the two lower voltage winding's in parallel.. Potentially two sparks per revolution unless you use a small chainsaw flywheel as your source. where you have one per rev. Nev

john.whiting
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Re: Maggy fix.

Postby john.whiting » Mon Mar 19, 2018 3:03 am

Thanks all,I want to keep the system looking original.......Im sure there was a comercial conversion used this idea at one time.But then I might be confused.......I was shown a miniature magneto for a model that used this system ,so maybe thats what Im thinking of.I know there are permag rotating magnet mags as replacement for the genuine article......in fact I think that is what the current BTH magneto is....Next item is to get hold of a AVO coil winding machine ,which a friend bought at a fleamarket for $10.Unfortunately ,he has passed away,and that makes asking to borrow the machine tricky.


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