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Dynamo testing

Well, thanks to Ron Pier's advice -

- I tried to motor the dyno and got success at the first attempt, but on the others it stood still. I checked the battery and there were 6,4 volts in it. Still connected, I turned it by hand and there it motored again, but I was unable to recreate again its self-motoring. So, before final death is declared, what will the best way be to test the dyno on a lathe? Would it be the same as if it was still mounted on the bike?
And is there a way to isolate the cause of the problem?
Thanks again for any help.

Re: Dynamo testing


Try a brief squirt of WD40 where the brushes contact the commutator and see if it motors again.

Do not use electrical cleaner, for some reason this seems to put a film on the commutator.

On my dynamo, sometimes it will not put out a charge, but this seems to do the trick.



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Re: Dynamo testing

Thank you Patrick.
I just "washed" it with WD40, still the same situation.

Re: Dynamo testing

Hello Michael,

I would not try WD40, as oil is an insulator.
I do not argue with facts, of course, if it did any good
To someone's experience, but generally, a good contact cleaner does just that.

As to your motoring issue:

1. May be the field is weak and shorten somewhere.
You can test its resistance. It should be:
2.8 Ohms for the E2L (60W)
3.2 Ohms For the E3N (40W)
2. The brushes should move smoothly.
Spring tension 16-20 Oz.
3. There may also be something wrong with the brushes.
Are they new? maybe the material is not correct.
There are few kind of materials for brushes.(But probably not the issue here)
If you have an old pair, I would try it...
4. There can also be a problem with few of the armature windings,
So when the brushes are touching either side of it,
There is not always magnetic flux to start motoring,
Unless you give it a "push".
It can be tested with a multimeter, but best to test with a glower.

Please see[2].pdf
For more info.

Best regards,

Re: Dynamo testing

Shalom Noam, that was very helpfull, appreciate it.
Thanks a lot, I will try all.
Best - Michael

Re: Dynamo testing

Hello Michael.

Hope it helps.

Reading my post again, I see I wrote "E2L", I meant E3L. of course.

Are you Michael Steinmann, asked here before regarding the sidecar and located in Israel?
If so, if you would like, please send me an e-mail or put your phone No. here,
(I currently have some problems with my cellphone...)
And I may be able help you further.

Best regards,

email (option):

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