Magdyno parts

[Barrie]

I am after an armature for the dynamo on my mag dyno (MN2) , I’ve got the part number for this item, does it cross over to another number, or is there a substitute part?
Is it the case that no new part is available, and it’s a rewind job
Barrie

[Tman]

I’d always get the existing item rewound, as it’s the only one guaranteed to fit perfectly. Too many “new” replacements seem to come from Far-Eastern pattern parts suppliers, where close enough is good enough… 🙄

[Barrie]

Thank you for you reply Tman

[efr215]

Magnetos despite having been around for 100 years or more are still something of a “dark art” to most of us and it seems there are precious few undertakings that have either the equipment and/or the in-depth knowledge to make a good job of a re-build. Therefore entrust such work only to someone with a proven track record.

Before considering a rewind it would worthwhile having the windings checked as they may well still be good.

One major pitfall is the capacitor buried within the armature. The original capacitor was a component that could be expected to well outlive the machine it was fitted to BUT its very construction meant that it had a life-span and one rather less than the 50+ years of even the most youthful of magnetos we meet today. Even a ‘new old stock’ unused OEM capacitor is well past its ‘sell by date’ now and should not be used. What makes matters even more difficult is that there are a very few modern capacitors that can stand up to what is a very onerous task. So make very sure what your repairer is fitting.

If the armature is removed from a magneto for any reason there will be an inevitable loss of 20% or more in the strength of the magnet(s) in the magneto. Do not imagine that a ‘keeper’ will save the day, the loss occurs in microseconds. The magneto on reassembly may well still work but its output will be proportionally reduced. The answer of course is to re-magnetise the unit but this requires an exceedingly large, powerful and expensive re-magnetiser particularly for the more modern magnetic material, how many re-builders have such a unit? I note that there are some people offering an “internal” re-magnetising service but given that the instrument has to be withdrawn before the armature can be replaced and the almost instant losses previously mentioned it is had to see how this method can be more than marginally effective.

[Barrie]

Efr , if you had bothered to read my question properly i’m not doing the magneto,i’m doing the DYNAMO ! I do my own repairs wherever possible ,at this moment in time I am correcting other peoples work, this mag dyno is a “rebuilt unit” , funny that, when the dynamo was not assembled correctly so it could not have given an output on test.

[Tman]

If the armature is removed from a magneto for any reason there will be an inevitable loss of 20% or more in the strength of the magnet(s) in the magneto. Do not imagine that a ‘keeper’ will save the day, the loss occurs in microseconds.

I don’t know where you’ve got this from, but how then is/was the mag manufactured without this “loss” occurring? Wouldn’t this apparent loss be inevitable, given the construction of the mag?
On this basis almost every mag in existence will have suffered similarly, but I have bikes with mags (as apparently do many of thousands of other riders) and they happily light up the mixture most satisfactorily.

[Barrie]

Thank you Tman, on the subject of capacitors , supplementary capacitors are available for a quick easy repair on magnetos

[chris wastell]

Hi Barrie. When they said the Dynamo was rebuilt, maybe it was…. but not necessarily properly! 🙁

[Barrie]

Exactly, human error was the factor.

[efr215]

Barrie — Sorry about that! Another ‘senior moment’! I saw the “Mag” in “Magdyno parts” and went onto autopilot.

I don’t know where you’ve got this from, but how then is/was the mag manufactured without this “loss” occurring? Wouldn’t this apparent loss be inevitable, given the construction of the mag?
On this basis almost every mag in existence will have suffered similarly, but I have bikes with mags (as apparently do many of thousands of other riders) and they happily light up the mixture most satisfactorily.

The magneto is magnetised when fully assembled. I would refer you to the Lucas publication “Remagnetisation of Magnetos”

[Tman]

Makes you wonder how all those many thousands of mags have managed to keep going over the last 60+ years, given that even a simple bearing regrease would need the armature removing.
Another of those situations where pragmatic reality has to overcome ideal world theory.

[Barrie]

Well luckily I’m not stripping the magneto, which does appear to have been done reasonably well
apart from one cracked H/T pickup which was replaced, and with the help of a damp morning I found it pretty quickly.
Hopefully next week I should of overhauled the dynamo and I should be able to take the machine for an amble

[Stan Thomas]

THE best armature rewinder is Tony Cooper in Brierley Hill (‘phone number 0121 559 2405) Tony acquired all the relevant machinery, tools and parts when Lucas closed their service dept down.

How the magneto is assembled without any reduction in magnetism is simple. It’s magnetised after assemby.

You stand it on a re-magnetising coil, switch the coil on, pick up the magneto a walk away backwards out of the magnetic field – making sure you don’t go arse over tip. See Roy Lambert, he has a re-magnetising coil.

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