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magneto weights

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johncat07
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i am having trouble with the magneto fitted to my d6 8u pony. its seems to have good spark for 2-3 revolutions and then the spark is weak or none. however i purchased a magneto off ebay (good core rebuilder), i set the gap on points gave it a whirl while in the vice sitting upright great spark. when i flip it upside down to fit back on pony a weight slides out of opening on arrestor plate and prevents it from turning. i am wishing to take the good drive coupling assembly+weights of bad spark mag and transfer it onto good. can it be done and how?
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Fri, Apr 29, 2011 2:17 PM
STEPHEN
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The plate behind the impulse weights may need to be removed & reinstalled 180 Deg to convert the mag to upside down operation. Also need to check that the rotation is correct for your tractor.
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Fri, Apr 29, 2011 3:49 PM
John from Fresno
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Reply to STEPHEN:
The plate behind the impulse weights may need to be removed & reinstalled 180 Deg to convert the mag to upside down operation. Also need to check that the rotation is correct for your tractor.
Johncat07,

At the magnetos the same? Some of the D6's (early) had horizontal mounting and other (late) had the mounting at a slight angle. See pics. I don't think you can just rotate the impulse. You would be changing when the impluse winds ups and releases in relation to the points on the breaker plate. Becuase as you move the body of the mag, you rotate the breaker plate and points in relation to the cam on the shaft. :confused2: If you have a D6 8U you are probably looking for a Bosch MJK mag. There is an Eismann that looks like it would work , but the impluse only works if the mounting bolts are horizontal. This one is for the erlier D6's like a 5R.
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Fri, Apr 29, 2011 8:20 PM
Old Magnet
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Reply to John from Fresno:
Johncat07,

At the magnetos the same? Some of the D6's (early) had horizontal mounting and other (late) had the mounting at a slight angle. See pics. I don't think you can just rotate the impulse. You would be changing when the impluse winds ups and releases in relation to the points on the breaker plate. Becuase as you move the body of the mag, you rotate the breaker plate and points in relation to the cam on the shaft. :confused2: If you have a D6 8U you are probably looking for a Bosch MJK mag. There is an Eismann that looks like it would work , but the impluse only works if the mounting bolts are horizontal. This one is for the erlier D6's like a 5R.
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I can only relate to the AB mag but I suspect the Eisemann is similar.
The impulse couplings are not the same for the early and late D6 and only a few parts are interchangeable and none are adjustable.

The impulse event start is based on gravity so the arrester plate slot has to be on the bottom. To obtain this on the slant version the housing (spring), Hub and arrester plate are different.

My list of Eisemann applications and AB interchanges doesn't show an Eisemann application for the late D6, just the RC-2H for the early units.
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Fri, Apr 29, 2011 9:33 PM
johncat07
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Reply to Old Magnet:
I can only relate to the AB mag but I suspect the Eisemann is similar.
The impulse couplings are not the same for the early and late D6 and only a few parts are interchangeable and none are adjustable.

The impulse event start is based on gravity so the arrester plate slot has to be on the bottom. To obtain this on the slant version the housing (spring), Hub and arrester plate are different.

My list of Eisemann applications and AB interchanges doesn't show an Eisemann application for the late D6, just the RC-2H for the early units.
the magneto mounts at a slight angle.both magnetos spin in the same direction. both have opening in arrestor plate at bottom. both magnetos are bosch mjk the one fitted is 412360B-410 and the replacement is 4/2306C-410. the little slide weight seems too lose it just falls out. if you place the magneto in any other position it will spin without the problem, but you hear the slide weight scraping around inside of arrestor plate.
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Sat, Apr 30, 2011 10:26 AM
zootownjeepguy
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Reply to johncat07:
the magneto mounts at a slight angle.both magnetos spin in the same direction. both have opening in arrestor plate at bottom. both magnetos are bosch mjk the one fitted is 412360B-410 and the replacement is 4/2306C-410. the little slide weight seems too lose it just falls out. if you place the magneto in any other position it will spin without the problem, but you hear the slide weight scraping around inside of arrestor plate.
Will the coil and condenser from the new mag fit in the original one? If it's the same make and type of magneto that may be the easiest way to go.
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Sat, Apr 30, 2011 8:09 PM
Old Magnet
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Reply to zootownjeepguy:
Will the coil and condenser from the new mag fit in the original one? If it's the same make and type of magneto that may be the easiest way to go.
Those are the correct mags for the later D6. Have you had the unit apart to check for damage of the hub, weights and cam?
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Sat, Apr 30, 2011 10:23 PM
johncat07
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Reply to Old Magnet:
Those are the correct mags for the later D6. Have you had the unit apart to check for damage of the hub, weights and cam?
[attachment=8924]01052011.jpg[/attachment][attachment=8927]01052011(003).jpg[/attachment][attachment=8926]01052011(001).jpg[/attachment][attachment=8925]01052011(002).jpg[/attachment]
(new mag second pic from right, old fourth pic from right)

removed couplings off both magnetos, weights and plate all facing with letter C up. and the letter A down. however on replacement mag the plate was loose from coupling, so i placed in back where it should be same problem. i noticed on old mag the arrester plate has a gouge where the weight catches on replacement. ( as per photos ) i then flipped weights and plate in replacement mag so the letter A was facing up. seems to work, still heat the small end of the weights scraping but when fitted and running i imagine the weight would slide towards the larger/heavier end eliminating the scraping.
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Sun, May 1, 2011 6:51 AM
Old Magnet
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Reply to johncat07:
[attachment=8924]01052011.jpg[/attachment][attachment=8927]01052011(003).jpg[/attachment][attachment=8926]01052011(001).jpg[/attachment][attachment=8925]01052011(002).jpg[/attachment]
(new mag second pic from right, old fourth pic from right)

removed couplings off both magnetos, weights and plate all facing with letter C up. and the letter A down. however on replacement mag the plate was loose from coupling, so i placed in back where it should be same problem. i noticed on old mag the arrester plate has a gouge where the weight catches on replacement. ( as per photos ) i then flipped weights and plate in replacement mag so the letter A was facing up. seems to work, still heat the small end of the weights scraping but when fitted and running i imagine the weight would slide towards the larger/heavier end eliminating the scraping.
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Whoa there......lets back up a little.
The "A" and "C" are AB's designation for anticlockwise and clockwise rotation magnetos. You don't want to mix these parts. On these mags the "C" on the fibre drive gear, weights and cam (that you refer to as a plate) should face out. The cam should also be fairly loose on the hub and is held in position when assembled.

The weights are part of the ignition advance mechanism. In the at rest position they drop down in the hub slots with one leg triggering the wind up process for the impulse spring (and released by the cam). This also simultaneously retards the spark to minimize the chance of back firing. When the mag is up to 180 rpm or so centrifugal force moves the weights to the other end of the hub slots for normal timing.

If the weights are dragging on the arrester it's most likely due to wear in the hub slots and on the weight lugs. They do run close but should not rub. I have also seen units with damaged hubs, especially the ear tab, bent weights and dents to the arrester hub.

They really are a pretty ingeneous device but can be finiky if everything isn' right.
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Sun, May 1, 2011 8:12 AM
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