Author Topic: magneto rotation  (Read 5376 times)

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Offline steveale

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magneto rotation
« on: 20 Mar 2015 at 16:01 »
I've searched but not seen this question directly addressed.  I have the opportunity to purchase a spare but different mag to my original, it is on a complete motor which would also serve as my spares source.  My original is the Bosch ZA2 with clockwise rotation.  The spare would be an EIC with counter-clockwise rotation.  Is it possible to change and not have problems?  I saw some reference that the advance cable may have improper slack with that type of replacement/change.  It would be spare for my upcoming cannonball run in 2016.

I don't want to purchase the motor at the asking price if the mag is a no-go.  thanks in advance.

Offline Frank Lyn

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Re: magneto rotation
« Reply #1 on: 20 Mar 2015 at 18:30 »
The points are completely different between a Clockwise and Counterclockwise Magneto. Most other things are the same.  Look at a set of points and you can immediately see that they have directionality.  Note that the direction of rotation is referenced to the DRIVE end so a set of points that are spinning clockwise are on a anti-clockwise machine.

The advance cable is a separate issue with a wide verity of implementations.  e.g. some pull to advance, others pull to retard.  I suspect that, ceterus paribus,  if you found a set of points to convert a CCW to a CC then if you originally pulled to advance, you would now pull to retard.

It is fortunate that points were fairly standard so there is a chance of finding a set to convert the magneto from CCW to CW (or the other way around.)  You may even be able to use the Bosch points on the EIC but I cannot say that for sure.


Offline steveale

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Re: magneto rotation
« Reply #2 on: 20 Mar 2015 at 20:04 »
So if I did a complete magneto swap with a unit that has the proper points and just reset the timing and insured the cable would operate properly there should be no issue with rotation?  I figured since they fire at 180 degrees the rotation wouldn't be critical like in a 45 degree magneto...

Am I missing anything?

Offline Earlyriders

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Re: magneto rotation
« Reply #3 on: 21 Mar 2015 at 04:31 »
Hi, changing rotation is not that simple. Besides changing the points plate the slip ring on the armature must be changed as well. Twin cylinder magnetos have a segmented brass ring on the slip ring (this is so that when the magneto sparks it doesn't spark on both plugs at the same time). If you just change the points plate when the points open there will be no corresponding brass segment on the slip riing to make contact with the HT pick up resulting in possible damage of the armature. Hope that this makes sense. Regards.

Offline shuswapkev

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Re: magneto rotation
« Reply #4 on: 21 Mar 2015 at 10:46 »

 my eic magneto sparks both plugs..same time
wouldn't spark at all until I put a bunch of rare earth magnets on my dead maggy magnet

Offline steveale

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Re: magneto rotation
« Reply #5 on: 21 Mar 2015 at 18:31 »
Sorry guys I am not making my question clear.  Can I swap a COMPLETE counterclockwise EIC in place of a COMPLETE  clockwise Bosch za2. No part/piece swapping between the two.

Offline Earlyriders

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Re: magneto rotation
« Reply #6 on: 21 Mar 2015 at 18:50 »
Simply - no. Regards.

Offline eddie

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Re: magneto rotation
« Reply #7 on: 21 Mar 2015 at 19:24 »
Hi,
          I am a little confused by your initial posting in this thread - you say you have found another engine complete with a magneto, but the mag is of the opposite rotation. Now, all 2¾HP Douglases from 1912 onwards had the same rotation magnetos, so are you assuming this second mag is of the wrong rotation just because it is stamped with an arrow showing that direction? (it could already have been reversed!). With regard to the different make - Bosch mags were the preferred magneto in the early 1900's but with the onset of World War 1, supplies to Britain and it's allies soon dried up, so several manufacturers in England started producing replacements - EIC being one of them.
 
      Regards,
                   Eddie.

Offline steveale

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Re: magneto rotation
« Reply #8 on: 22 Mar 2015 at 00:20 »
Thank Eddie,  the engine is a 1920 according to SN.  The eic mag has a counterclockwise arrow at the back top of the mag.  I just assumed this arrow would be correct.  The engine is unknown, it could have just been parted together.  I was only looking at it for spare parts for my bike for the endurance run.  It's also my understanding that most engine components for 2 3/4 machines were fairly interchangeable from the teens into the early 20's.  As always thanks for your insights, there are not a lot of experts on these old gals...

Offline douglas1947

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Re: magneto rotation
« Reply #9 on: 22 Mar 2015 at 17:10 »
The main components of a clockwise or anti clockwise magnetos are the same.

The difference are the cam ring (and position of the points on the plate), because the power for a strong spark is only at an special point, when you turn the armature.

When you turn the armature the wrong way, you got a weak spark.

Are you shure for the direction of the magneto?

Michael

Offline douglas1947

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Re: magneto rotation
« Reply #10 on: 22 Mar 2015 at 17:13 »
The main components of a clockwise or anti clockwise magnetos are the same.

The difference are the cam ring (and position of the points on the plate), because the power for a strong spark is only at an special point, when you turn the armature.

When you turn the armature the wrong way, you got a weak spark.

Are you shure for the direction of the magneto?

Michael

 

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