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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

Bosch Du4 and AT4?


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  #1  
Old 03-21-2017, 09:43:22 PM
BobM BobM is offline
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Default Bosch Du4 and AT4?

First what parts do I need to Change rotation on the DU4
Need anti clockwise when done also source for an Impulse.
I also have an AT4 mag ready to go but know nothing about it
So any info be great.
Need info on timing and point gap on either mag
Thanks in advance
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Old 03-23-2017, 08:57:52 PM
Craig Gillingham Craig Gillingham is offline
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Default Re: Bosch Du4 and AT4?

Here's an old post where a similar topic has been covered before. Basically the easiest way to change the rotation on a DU4 is to replace the point assembly and re-time the distributor-armature gear. The gears should be marked with an 'L' 'R', or 'CW' ACW' etc, and I know that sometimes the armature gear is marked with a chamfered tooth, or a dot There were a few different types of Bosch impulses used, some of them are able to be changed clockwise to anti-clockwise, some of the other types of Bosch impulses I'm not sure about.

https://www.smokstak.com/forum/showthread.php?t=112927
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Old 03-25-2017, 01:23:11 AM
BobM BobM is offline
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Default Re: Bosch Du4 and AT4?

Thanks Craig I found that in a search but don't you need the correct parts to do the change
And is an at4 good replacement mag
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Old 03-25-2017, 06:50:06 PM
Craig Gillingham Craig Gillingham is offline
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Default Re: Bosch Du4 and AT4?

Bob, yes, using this method you'll the correct point assembly to change the magneto rotation.

I remember reading of one someone who re-timed their existing point assembly to the armature to change the rotation of the magneto. The point plate will have a key where it's timed to the armature keyway to open the points at the maximum current point, so what they would have done is taken the key off the point plate (filed it off?) and rotated the point plate so the points opened at maximum current for the rotation they wanted. Whether they put a new key on the point plate, I don't know. And it would mean that the fibre block on the contact arm would be pushing on the cam lobes instead of dragging. I've never tried this idea before, and I'm sure it would work, however, I don't know what problems could arise from this; does it lead to excessive wear on the contact arm, etc? I don't know for sure. Basically, you're on your own if you decide to try it.

I can't help with AT4 info, I know they will interchange with a DU4 regarding spindle height, bolt pattern, etc., but there'll be others on here that have had experience with AT4 magnetos that may be able to help.
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