Looking for electrical help.

I have heard of "flashing" the magdyno as meaning either setting the polarity of the system to negative or positive earth or renewing the field magnetism that is lost when a bike sits for long periods. I need advice on the loss of of magnetism after sitting. Symptoms are no lights or horn, ammeter stays in center. A 5-mile run, some at high revs doesn't kick it in.

My regulator (from Podtronics) has instructions for renewing the magnetism by (1) disconnecting the regulator (2) jumper wire between the dynamo F terminal and ground ("chassis earth") (3) connect a wire to battery positive terminal (4) touch that wire to dynamo D terminal for about a second (5) reconnect regulator. The instruction then says: "This should be sufficient to get your electrical system charging again."

My battery is low -- it is new but has sat most of the past year. I will charge that as the first thing. After that, are the instructions above correct? How do I disconnect the regulator? There is a fuse between the battery and regulator--just take that out? Beyond that I can follow the instructions-- is there anything else I should do?

My magdyno output reading following the M20 instruction sheets is below 1 volt. Is it likely the fully charged battery and this procedure will put the charging output reading back to 10++ when revving?

The magdyno was completely rebuilt 1-2 years ago and it hasn't been run much at all since then.

Thanks in advance for any help.

Rod
Hancock NH

email (option): perryhq@frontiernet.net

Hi Rod,

You can find the instruction for re-polarizing also here,
On the tech' section:

http://wdbsa.nl/lucas_dynamo.htm

In order to disconnect the regulator,
Do not bother to do it from the regulator side.
Just pull out the "D" and "F" wires from the dynamo,
And nothing is connected to the regulator anymore.

The reason for not charging, can also be down to the weak batt.
Some electronic regulators would work only if your battery
Has a minimal charge to it. funny, but that's how it work..

If you want to check your dynamo on the bike, without taking it off,
You can start the bike, connect a "Y" shaped wire (I will explain.. )
With one end to the "D" connector of the dynamo, another end to the "F",
and you have another free end of the wire:

You can rev the engine a bit, and MOMENTARILY touch the bike's chassis.
If there is a spark all is good.

Another way is to take a lamp / bulb, touch one pole of it to the chassis,
And touch the other pole with the said wire.
As you rev up the engine, the bulb should light.

If the dynamo is off the bike, you can shorten the "F" and "D"
Using the same system, connect the remaining end to one pole of a battery,
And the body of the dynamo to the other pole.

The dynamo should motor.

Good luck,
Noam.

email (option): noam10@gmail.com

Hi Rod,

It's called flashing the dynamo, it has nothing to do with the magneto part. If you have had the battery off the bike just make sure you have it the correct way round. Turning the lights on without starting the engine will show a discharge on the ammeter, if it swings to charge without the engine running the battery is the wrong way round. If you ran it like this you will damage the regulator if its the solid state type.
Firstly disconnect the 2 wires from the dynamo (F&D) make sure you have marked them so you know which way they go back. Now get a piece of solid wire I use thick welding wire and make a loop and connect F&D on the dynamo together, connect a volt meter and connect one wire to the new wire loop and the other wire from the volt meter to a good earth ( i use the earth screw on the magneto end cover under the points cover). Start the bike give it a rev and the volt meter should read between 10 and 16 volts depending if you have a short dynamo 45W or the latter long dynamo 60W.
If you are neg earth the leads from the volt meter should be Neg to earth and + to your wire loop when the volt meter is showing a reading.
Flashing the dynamo will reverse the polarity of the dynamo. To do this you need a charged battery.
Re-polarizing the dynamo is as follows

For POSITIVE earth, disconnect the 2 wires from the dynamo F&D connect the + of the fully charged battery to a good earth and flash the F terminal (on the dynamo) with the negative wire of the battery.

For NEGATIVE earth, disconnect the 2 wires from the dynamo F&D connect the - of the fully charged battery to a good earth and flash the F terminal (on the dynamo) with the positive wire of the battery.

So to round it up you need a good output from the dynamo as above with the correct polarity before you connect the 2 wires back into the F&D terminals on the dynamo.
As i said you will damage a solid state regulator connecting it with the wrong polarity. The older mechanical regulators MCR1 and MCR2 will work either way round.

Hope it all makes sense.

Let use know how you get on with it.

Tim W

email (option): t.j.walker@btinternet.com

The key thing here is that electronic regulators cannot tolerate connection to an incorrectly polarized system. They are either +ve or -ve earth and the system must be set up to suit that..Most will also not last long if there is a short circuit...

It is important therefore, that the system is checked for short circuits and to establish that the polarity matches that of the regulator BEFORE connecting the regulator into the system and running the bike...

If you have inadvertently run with an incorrectly polarized dynamo you have probably already 'smoked' the regulator...Ian

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

Thanks to all for the information. The next issues for me are ….

The electrical is set up for -ve earth--I am quite sure of this. Could it be switched to +ve earth by mistake? How?

Does removing the battery to charge it require a new polarizing when it is re-installed?

Once i have a fully charged battery, should I "flash" the magneto to restore the field magnetism? Or just run the bike to see if the lights and horn come back?

This is complicated for me, and I want to do things right, so I would appreciate any advice.

email (option): perryhq@frontiernet.net

Rod,

You can tell if the battery has been connected the correct way round by following my previous instructions about watching which way the ammeter needle moves when you put the lights on (this is without starting the bike).
The set up on your bike cannot change polarity on its own. you do not need to flash the F terminal of the Dynamo (not the magneto) every time you take the battery off the bike.
If you read my above note fully you will see how it can be done, but as said in the last post if you have run it with the battery the wrong way round the solid state regulator will be cooked.

Tim W

email (option): t.j.walker@btinternet.com

For the sake of clarity the magdyno unit is divided into two separate electrical components joined together by a gear drive...

On top is the dynamo that provides current for lighting and charging the battery...

Underneath it is the magneto which provides the spark for ignition...The magneto plays no part (electrically) in the function of the dynamo and vice versa

The dynamo needs to be repolarised to suit the polarity of the system after an overhaul as a precautionary measure.
Also after a very long 'layup'..again as a precautionary measure...
and finally, in the case of an electronic regulator, if you change the regulator polarity from a negative to a positive earth unit or vice versa...

No other part of the system apart from the dynamo needs to be 'repolarised'...It is only necessary to make the battery connections correctly to suit the polarity required...So the negative side of the battery to the main earthing point for negative earth systems and the positive side to earth for positive earth systems...

All of this will be dictated by the polarity of the electronic regulator you have. The polarity of these units cannot be changed and the system must therefore be set up to match the regulator...Ian

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

Ian, how long do you consider a long lay-up to be ? Mine seems to lose it's residual magnetism after a month or less and need flashing before I can get anything out of it again...it then gives me an unregulated 8 or 9v just off tickover, so output seems OK once it's working.

What is the procedure Rik refers to in flashing the dynamo to renew residual magnetism after a layup?

Is that different than the procedure to re-polarize the dynamo? I understand that procedure now , and the risks of running if it is set up wrong.

Thanks again--
Rod

email (option): perryhq@frontiernet.net

Renewing residual magnetism,
Is the same procedure as re-polarize the dynamo.

In the first seconds of work,
Before the dynamo can start to produce electricity and energize the field coil,
It needs some small amount of magnetism to get going.
That would be the residual magnetism.
By polarizing, you get to chose if it would be N or S pole.

If your battery is full,
You first have to determine which kind of regulator you have-
(+) or (-) chassis, re-polarize once accordingly, just in order to know that all is correct,
And from there and on, you do not have to do it again, even if you change battery.

I have a WM20, 1945, which started charging after being in storage for 10 years,
Without doing anything, except installing a new battery.

Noam.

email (option): noam10@gmail.com