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D7 17a magneto

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3 years 5 months ago #222546 by wj-ihc
D7 17a magneto was created by wj-ihc
Have a 17a (11237) with a 5M4071 wico mag. Pony hasn't been ran in a few years and dad pulled the mag off to check it out and did not note the rotor alignment when he removed it. The operator manual I have (17A1-up) shows a different mag than what we have, as we do not have an "A" Mark. The pinion gear has two teeth side by side with a beveled edge, and the rotor has a raised Mark directly over a tooth. Seems they should be aligned, but we aren't getting much of nothing, a rare backfire. Have swapped wires (even fire cap). My next step would be to just ignore and potential markings and just try to get it on #1 compression and start trying to bring the rotor contact into line with the #1 terminal on cap and see what happens.
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3 years 5 months ago #222547 by wj-ihc
Replied by wj-ihc on topic D7 17a magneto
Pic
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3 years 5 months ago #222554 by neil
Replied by neil on topic D7 17a magneto
Yes even without the marks, you should be able to get it close by a) setting it so the points are just opening at the correct time in the crank rotation (I don't know what the specs are for that tractor), and b) that the rotor is pointing to the correct post. Check both cylinders when you set the timing - they both need to be correct for your timing to be right - kind of obvious but that'll tell you if you're on the mark or 180 out. If that checks out, then the timing should no longer be an issue.

Cheers,
Neil

Pittsford, NY

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3 years 5 months ago #222568 by edb
Replied by edb on topic D7 17a magneto
Hi,
the mag in this link appears to have similar coarse gears as yours--down towards the bottom of the booklet is shown coarse toothed distributor plate.
Magneto gears are usually well marked for timing for either hand rotation that is :- CW--CCW Sometimes a beveled tooth end is used, a red painted groove white lettering for hand rotation and so on.
Once the internal timing of the mag. is settled the timing the mag would be as outlined in the grey OMI for an earlier edition mag. and much as you outlined above.
Am time pressed at present so I have not read thru the book but would be sure your query would be answered there.

It also seems by your pix that there is moisture damage and one would assume this has been addressed as also the points that appear to be seized in an open position.

oldcroak.com/xh-and-xhd-magneto-rx/

Hope this helps.
Cheers,
Eddie B.

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3 years 5 months ago - 3 years 5 months ago #222571 by Old Magnet
Replied by Old Magnet on topic D7 17a magneto
Your timing approach is correct, rotor mark between the two beveled teeth on the small gear.
The small gear beveled teeth go behind the rotor.

Beware this info was furnished by others. Seems more logical that the rotor timing indicator would be placed between the two beveled teeth. Probably wouldn't matter if your set to fire at that position. Other comments or corrections???

For reference the Cat 5M4071 magneto is a Wico model XH-2450CS
Will also require correct impulse timing.

Edit: After doing some more reading I found stated "the marked tooth goes between the two beveled teeth" I'm assuming that marked tooth is on the large gear mounted to the rotor. Not the mark on the rotor itself?
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Last edit: 3 years 5 months ago by Old Magnet.

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