[magneto]

Further to # 6.
Coil failure.

Please refer to # 13, all that is explained holds for the above .

Condenser failure.

Condenser failure will reflect in the following symptoms;

Burning and frequent pitting of the points .

Misfire at high speeds.

Starting trouble once the engine is hot, but will start well on a cold engine.

The condenser used in a magneto is either a mica type or a foil paper type with a oil insulation.

The mica type is much superior and may work well after many years of service, and may get weak due to ingress of water or oil which causes the insulation to get weak due to corrosion.

The oil insulated condenser normally fails after a few years, even if it is unused and new.

I have never come across a good condenser of the oil type in my long experience, and all have been replaced .

The value of a magneto condenser is mostly a 0.33 MFD with voltage of about 600 v DC, and should be of a bi polar type.

The condensor can be checked for capicitance with a capacitance meter found in most multimeters.

To check the insulation, one would need a megger with a 500v range to check the resistance which should be infinity for a good condensor .

[magneto]

An interesting lesson on Magneto points;

I recently rewound a twin BMW magneto and the customer, complained that he was getting a very weak spark, so i rechecked the parameters on the test bench, and everything was normal, so the next thing was to remagnetise the magnet and recheck the timing, having done this still no luck, replaced the condenser, no go, then the customer tells me that he had replaced the point set with a new one, so on a hunch i tried the old point set and bang she started in the first kick.

Now the question, what was the difference between the old and the new set ?

On doing some research i have learned the the points used for battery operated coil ignition systems are made of a tungsten alloy, whereas the ones used for magnetos are based on a platinum alloy, due to their properties of low resistance .

How does one find out the difference, well the easiest method is to use a fine jewelers file, which will cut the platinum point, but will slip on the hard tungsten surface, or one can use a drop of nitric acid which will eat into the tungsten but will not affect the platinum.

More later. M.

[deutscheafrikar]

Dear Mr Ashar,
Thanks for all the info. Very interesting. In France there are more than a hundred BMW R12's which are used regularly. Some of them visited India in the late 90's to ride back from Mumbai. Then later did the Silk route and also recently rode in South America. I was curious as to where the French owners were getting their magnetos repaired.
Regards
Nigel

Originally Posted by magneto

Hi Nigel, sorry i did not answer you question about the French gentleman, Mr Michel DeThomasson, mdethomasson@wanadoo.fr, who is a world authority on magnetos and had come to India to judge the motorcycles for a VCCCI rally and was surprised to see all the magnetos on the cars and motorcycles working perfectly, on asking around as to who was responsible for this, someone pointed towards me and this was around 11 Pm in the evening.

[kylohere]

Hello!
There are quite a few who claim to be well versed with magnetos but I have yet to find someone who truly knows magnetos better than Mr. Magneto himself. My Matchless mag went to about three people, arriving back worse off than it was to begin with. That was until I got in touch with the man himself. Apart from doing a splendid job with it, I learned tonnes while seeing him work in his workshop, surrounded with stuff that would make any motorhead delirious. He's the most approachable man I know and he's happiest helping people with their mechanical woes. My Triumph mag has also been done by Mr. Magneto and it's ticking away perfectly. Thanks a tonne Mr Magneto (that sounds quite akin to a DC Comics superhero, really!) and I'm quite sorry for my little rant here.

Thanks and regards,
Kyle Pereira.

Oh, and lets not forget Mr Magneto's stable of some of the finest machines around...

Note from the Team-BHP Support Team : Please use the "edit" button if posting within 15 minutes of the first post, instead of creating another back-to-back post

[magneto]

Dear Nigel,
The R12 uses a Bosch magdynamo like the, "Lucas" ones used on Brit singles.

I have done couple of them, and i am working one one for harit.
These Bosch mags are of very high quality and would outlast the bike once they are subjected to proper reconditioning.

I am sure that there must be lots of reconditioners in Europe, but the surprising thing observed by me is whenever a BMW was restored in Europe, the coil was a original one and not a rewound one, like the R65 which was reconditioned in england by Bob Porecha, who is a BMW specialist in Birmingham. This is the very same coil i have rewound recently and mentioned earlier in the thread regarding points.

I believe that most BMW breakers are in Belgium and most people get their parts at a reasonable prices from there.

Do you have a link to the R12 tour,should be interesting .
Bye,
M

[deutscheafrikar]

Originally Posted by magneto

Do you have a link to the R12 tour,should be interesting .
Bye,
M

Dear Mr. Magneto
I can't find the latest one in South America I have it on the disk though, these are the earlier ones
Nigel

periples en R12

Google Translate

http://www.bmwclub.ca/IC/CouncilNews...ews_0104_e.pdf

[deutscheafrikar]

Dear Mr. Magneto,
Here is another link
Les routes de Moto-Net

Google Translate

[magneto]

Dear Deutscheafrikar ,
That was good reading as i do read a bit of french.
Doing 18000 Kms on a R12 with all that load sure needs lots of guts.

I have been busy with a huge backlog of magnetos and also i am in the process of storing my cars for the rains.

I think i should deal with the next subject on magneto problems which is worn out cams.

I have many a time told customers that their magneto timing was not proper, and they normally mistake that for the valve timing or the ignition timing .

There is a third timing which is the internal magneto timing. This timing is the position of the armature in relation with the magnet so that the magnetic flux is at its maximum position, so as to generate a high current in the coil, it is this very moment that the point has to open, so that a nice strong spark is generated on the secondary of the coil.
Now in case the cam is worn out on the leading edge, the result will be a late opening of the points resulting in a weak spark.

To some extent one can compensate this by reducing the gap in the point.

The other method is to change the position of the cam so as to advance it a bit to compensate for the wear .

I case it is too badly worn out, there is no go but to replace the cam.

It is very important to lubricate the cam with a good synthetic grease like the Wurth, HS 2000. so as to have a steady timing, and not a jerky movement of a dry cam.

That is all for today, Bye.
M

[deutscheafrikar]

Originally Posted by magneto

Dear Deutscheafrikar ,
That was good reading as i do read a bit of french.
There is a third timing which is the internal magneto timing. This timing is the position of the armature in relation with the magnet so that the magnetic flux is at its maximum position, so as to generate a high current in the coil, it is this very moment that the point has to open, so that a nice strong spark is generated on the secondary of the coil.M

Dear Mr Magneto

Your third timing is a very important point especially during kick starting the engine because then at the slow speed you can have the strongest spark which is need to start the engine.
I have a friend in Germany who is a fellow R12 owner, he has done some research on the Bosch Mag-Dyn for the R12. He is not yet finished though. This is his site
Bosch D-Magneto
DMAG: Producer
Maybe you could help him complete his research.
Regards
Nigel

[magneto]

Dear Nigel,
Absolutely on the dot, as one does need a strong spark to start a machine, and the rotation speed is pretty slow, and of course most old machines do have some issues and are not in peak shape.

One more interesting thing, almost all racing machines used magnetos and not the coil point kittering system using a battery.
This may be for two reasons, one is of course due to the weight of the dynamo/battery, and the second being that the current actually increases with rpm in magnetos and decreases on a coil/point system.

Did you know that under compression a spark deteriorates as compared to a strong spark in open air, which means that you need a stronger spark for a high compression engine, hence the term racing magnet with a slightly better performance then the normal one.

bye. M.

[Rehaan]

Originally Posted by magneto

.....One more interesting thing, almost all racing machines used magnetos and not the coil point kittering system using a battery.
This may be for two reasons, one is of course due to the weight of the dynamo/battery, and the second being that the current actually increases with rpm in magnetos and decreases on a coil/point system.

Did you know that under compression a spark deteriorates as compared to a strong spark in open air, which means that you need a stronger spark for a high compression engine, hence the term racing magnet with a slightly better performance then the normal one......

Super info magneto! Thanks for sharing.

Once again, it would be great if you could put up some photographs or diagrams of magnetos so that readers can have a better idea of what you're talking about.

Thanks,
R

[magneto]

Thanks Rehan,
I will try to add pics in future,let me have a go at it, to see how it works out, by posting pics of some coils in the condition i have received and after processing .



Bye.
M.

[wasif]

Pardon my asking but did they start out as three and ended as two ???

[deutscheafrikar]

Nope, they start out as one each, and they end up as one too.

[magneto]

Dear Wasif,
I think you got the point.
Closer look with two in the pic.
M.