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Magnetos, Ignition Coils and Spark Plugs Discussion about magnetos, buzz coils, spark plugs, ignitors and low tension coils.

Magnetos, Ignition Coils and Spark Plugs

Eisemann magneto for an Allis 20-35?


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  #1  
Old 08-21-2015, 11:11:53 PM
Jacob WI Jacob WI is offline
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Default Eisemann magneto for an Allis 20-35?

Hi all,

I have what I hope is an easy question for you. I have a 1927 Allis Chalmers 20-35 short fender. I am trying to figure out what type of magneto I should be looking for, as it is missing on my tractor.

From what I have read on other posts (mainly from this site) It should be an Eisemann GS4 I believe. Is this correct?

If so, I have also been told, and read, that it should be an ANTI-clockwise rotation magneto. Are ALL GS4 mags Anti-clockwise? And if not, how can I tell if it is?

OK, next (again assuming the GS4 is correct) I have read that there are three editions of the GS4. What editions were used for what years, or what edition should I have on my 1927 tractor?

I hope this makes sense, and you all can help me Thank you!
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Old 08-24-2015, 02:50:49 PM
Mitch Malcolm Mitch Malcolm is offline
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Default Re: Eisemann magneto for an Allis 20-35?

In my experience you need a GV 4 a bigger mag than a GS series,
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Old 08-24-2015, 06:19:14 PM
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FWurth FWurth is offline
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Default Re: Eisemann magneto for an Allis 20-35?

The Eisemann mag never was much when new, most were changed over to the Bosch or Fairbanks early on in order to have a reliable tractor when they were still working them. The anti clockwise rotation refers to the rotation of the mag at the impulse, simply stated the mag rotates the opposite direction compared to most other tractors. This is because the timing gear train of the motor has an extra gear in the drive that causes it to rotate the opposite direction.
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Old 08-25-2015, 03:48:32 AM
Craig Gillingham Craig Gillingham is offline
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Default Re: Eisemann magneto for an Allis 20-35?

Eisemann GS4 magnetos were made in both clockwise, and anti-clockwise. As Fwurth stated, the rotation is nominated from the drive end.

With a GS4 magneto, the only difference between a CW or ACW magneto is the point assembly. Possibly the arrow stamped on the front cover or oil cap, but that isn't a major issue. The distributor rotor gear has to be timed to the armature gear for CW or ACW, but there should be timing marks on the rotor gear, and a timing mark on the armature gear.

The most important thing is the point assembly. These are photos of CW and ACW Eisemann point assemblies. The one on the left is for a clockwise magneto. The one on the right is for an anti-clockwise magneto, basically, one is the reverse of the other. The way you tell is that the fibre block on the contact arm should trail behind the pivot point on the contact arm, when the armature is in motion. I hope that makes sense.
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Old 08-25-2015, 09:00:08 PM
Jacob WI Jacob WI is offline
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Default Re: Eisemann magneto for an Allis 20-35?

Quote:
Originally Posted by Craig Gillingham View Post
Eisemann GS4 magnetos were made in both clockwise, and anti-clockwise. As Fwurth stated, the rotation is nominated from the drive end.

With a GS4 magneto, the only difference between a CW or ACW magneto is the point assembly. Possibly the arrow stamped on the front cover or oil cap, but that isn't a major issue. The distributor rotor gear has to be timed to the armature gear for CW or ACW, but there should be timing marks on the rotor gear, and a timing mark on the armature gear.

The most important thing is the point assembly. These are photos of CW and ACW Eisemann point assemblies. The one on the left is for a clockwise magneto. The one on the right is for an anti-clockwise magneto, basically, one is the reverse of the other. The way you tell is that the fibre block on the contact arm should trail behind the pivot point on the contact arm, when the armature is in motion. I hope that makes sense.
Thank you for the info, I knew someone would know!
So let me make sure I understand what you are saying. Does this mean that I can find ANY GS4 (CW or ACW) and it is just a matter of timing it and putting the correct ACW point assembly on it for it to work correctly?
Or is it not that simple?

I realise finding the correct ACW mag is the easiest, but you know how that goes sometime

Anyone have any info on what years which editions were used?

Thanks!
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Old 08-26-2015, 12:12:32 AM
Craig Gillingham Craig Gillingham is offline
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Default Re: Eisemann magneto for an Allis 20-35?

Quote:
So let me make sure I understand what you are saying. Does this mean that I can find ANY GS4 (CW or ACW) and it is just a matter of timing it and putting the correct ACW point assembly on it for it to work correctly?
Yep, simple as that. A lot of the rotating armature 4 cylinder magnetos from that era are the same. The armature and the cam ring will be the same for both CW and ACW.
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Old 08-26-2015, 12:21:46 AM
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FWurth FWurth is offline
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Default Re: Eisemann magneto for an Allis 20-35?

You still have to deal with the impulse drive. The drive lugs will only engage when turned the direction intended. Not sure if they are reversible.
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Old 08-26-2015, 02:35:48 AM
Craig Gillingham Craig Gillingham is offline
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Default Re: Eisemann magneto for an Allis 20-35?

Quote:
You still have to deal with the impulse drive. The drive lugs will only engage when turned the direction intended. Not sure if they are reversible.
Good point, I'd overlooked that.
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Old 08-26-2015, 01:13:16 PM
stufforbud stufforbud is offline
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Default Re: Eisemann magneto for an Allis 20-35?

Most of the early Eisemann impulses are not reversible.
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