While restoring the bike (a procedure that took many years), the dynamo was sent over to the UK some years ago for a complete overhaul that included new winding.
The light system was fine for a few rides and then past out on the sudden taking the unlucky battery with it.
Now I have a smelly burnt dynamo and an non-chargeable dead battery.
I need help with sourcing down the problem and the cause for it.
Any help is much appreciated.
Regards – Michael.

email (option): michasteinmann@gmail.com

The chances are that you are using a mechanical regulator. If as can happen the cut-out points remained closed with the engine not running, then the dynamo will attempt to motor which it will be unable to do. The windings will burn out and there would have been a dead short on the battery.

I agree with Ian,
And another reason can be- (especially if it happened while driving)-
A regulator that charges to a much higher
Voltage than needed, "Boil" the battery, and strain the dynamo
As it tries to charge the battery to a higher voltage than it is rated to,
Leading to constant maximum charging.(Like a 12V reg for 6V Batt)
This would melt the soldering down, and may cause the armature winding
To get heated and melt, or the insolating lacquer / varnish on it
To peel off due to heat, and cause a short-circuits between windings.

Or-
The same effect caused by a lose wire that was shorting to the chassis,
Leading to the same affect while charging.

Noam.

email (option): noam10@gmail.com

Michael
If you are up to doing the work yourself, I can email you all the relevant Lucas Service Notes on the affected equip. ie dynamo regulator and battery.
Keith H

I have done the same thing in the past...I trashed a NOS Lucas dynamo (that had been fully stripped and tested prior to use) during a 15 mile ride home from work one night...

The culprit was the regulator which, it turned out, had failed but on maximum output...Result a boiled battery and a dynamo that was so comprehensively melted that the lower part of the tufnol brush holder plate disintegrated...

What type of regulator were you using?....Ian

email (option): ian@wright52.plus.com

Thanks a lot guys for all the help.
If the regulator is to blame, then what do you guys use on your ladies? I'm sure it's an original Lucas type on mine, but don't know what part number. Will check tomorrow.

email (option): michasteinmann@gmail.com

Hi Micha,

It should be either an MRC1 or MRC2 if it is the original.

I am offering my help again with the regulator,
But first you would need to redo the dynamo.
Many M20s use the 6V "Bosch" WV beetle type regulator,
(Which also demands a minor electrical wiring change inside the dynamo)

If you can't find someone to do it locally in Israel,
(Not due to lack of technology, but because the guys like to work
With standard armatures, which they have the pattern for)
You can buy a complete new manufactured armature in a reasonable price on eBay.

Second thing to check, is if the field coil did not also boil itself to death..

Noam.

email (option): noam10@gmail.com