H4 mag (counterclockwise impulse)

sgtbull · Nov 9, 2011

I recently acquired, and rebuilt, an H-4 magneto, only to later realize it wouldn't work on my H tractor, as it had a counterclockwise impulse. (yes, I know... I should have noticed that, but, I didn't... life goes on.) Really sucks, as it has an awesome spark.
They are surprisingly simple mags. What tractors do these fit? It has a "D" suffix on the mag serial # and I've been told that it fits both MD and W series tractors. Is that correct?
I have no desire to own an MD, but I'd like a W-4, in which case I'd just put this on the shelf and go on. IF I have no use for it, I"ll probably trade it off or sell it. Is it worth more than a regular H-4?

Anonymous-0 · Nov 9, 2011

Don t know for sure but I ll bet someone knows how to change it to clockwise. Probably in a manual somewhere.

Tom Fleming · Nov 9, 2011

Ok, H4 mags with serial numbers ending with a "D" are for the gas start diesels. They are counter clockwise rotation.

You can also reverse them to run clockwise. Remove impulse unit. reverse the pawl arms. Pull the pawl stop pin, install it on the other side. reinstall impulse. Then disaseemble rotor. change timing on it to the "R" mark. resassemble.

Good to go.

However, you are better served to sell the diesel H4 to someone looking for one, and buy a gasoline H4. IMHO.

Alont · Nov 9, 2011

I have worked on some mags in the distant past and
forget the details.
The direction of rotation could be reversed by altering the relationship between rotor and the points opening.

Perhaps an e-mail to the link would confirm/deny whether the change is possible
Untitled URL Link

Owen Aaland · Nov 9, 2011

In addition to the gas start diesels the W9 and T9 also use CCW rotation magnetos.

John M · Nov 9, 2011

Wont fit any gas engine. Well, sont work without the modifications already mentioned.

sgtbull · Nov 9, 2011

Already looked at switching the impulse stop pin, but the right side of the rear plate is not drilled to accept one. I suppose I could change out the rear plate, but was told that the armature was actually slightly different than the clockwise H-4, with the difference in the cam for the points. I noticed that the impulse cup appears to be different too, with an "L" stamped in it.
It sounds like it won't fit a W-4,which is really the only W series I'd be interested in, so I'll probably see if I can find someone needing one for a MD and swap or sell it. Hate to screw it up trying to modify it, when I'm guessing they aren't as common as traditional H-4s.

Tom Fleming · Nov 9, 2011

Ping Nebraska Kirk. I had a "D" H4, and he worked a deal with me. I got a CW H4 and he got a CCW H4. We were both happy.

John - OH · Nov 9, 2011

So correct me if I'm wrong. If I wanted I could take a cw H4 and turn it into a ccw H4? Just asking to know if it works both ways.

Owen Aaland · Nov 9, 2011

(quoted from post at 21:34:20 11/09/11) Wont fit any gas engine. Well, sont work without the modifications already mentioned.

Except the 9 series, the W9 and T9. Those gas engines also use a CCW magneto.

Tom Fleming · Nov 10, 2011

the conersion can go "both ways", however, it is not easy. you basicaly have to "reverse" the operation of the impulse. that requires moving the impulse stop pin to the other side. reversing the pawls, and all that goes with that.

to me, it is easier and simpler to just get the right mag. However, it can be done. I chose NOT to do that on one that I had.

Bob · Nov 10, 2011

Point cam/rotor alignment for CW and CCW is covered in the manual at the link below, pages 49 and 50.
http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html

Tom Fleming · Nov 10, 2011

Good point Bob, forgot about the cam. However, since it is a press fit, easy to adjust.

H4 mag (counterclockwise impulse)

sgtbull

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Anonymous-0

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Tom Fleming

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Alont

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Owen Aaland

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John M

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sgtbull

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Tom Fleming

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John - OH

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Tom Fleming

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Bob

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