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MD Magneto Help

I

IAtractorKid

Member
Hey guys! Ok so I am going to my parents farm tomorrow and hoping I can get my MD back into comission. A month ago, it started up and ran perfect and then the next weekend it would not start; no spark out of the coil. Plugs and wires (including the manifold switch wire) are new, cap and rotor were in good shape but thats all the farther I got. I have zero experience working on a magneto so if someone could walk me through it that would be great!

P.S. - Tractor is 12V if that makes any difference. Thanks!!!
 
Did you use copper core wires? And, what is a "manifole switch"? Next I would check the ingnition points. If you pull off the cap and rotor, you will see a raised round area around the shaft with two screws, leave those screws alone. Split the magneto just below the cap by removing the three screws, two inside under the cap, and one outside. Then set the points to speck. Crank the engine to see if the points then spark.
Best Regards,
Charlie
 
MDs have a cutoff so that the mag doesn't spark and wear out points when the engine is running on diesel. Also, all MDs were 12 volt from the factory.

I think that manifold switch can go bad. I would guess you can just unhook the wire to double check that it isn't the switch.
 
I unhooked the manifold switch wire and it made no
difference; still no spark. I oiled the mag drive
and impulse coupling, filed the rotor and inside
of cap, filed and reset points to .013" as per my
manual. Cleaned and greased as per the manuals
instructions too. None of this made any
difference.

What next????

I did notice the coil wire is cloth braid so I am
guessing the coil has a few years on it! How do I
get it out and is there any way to test it? Thanks
for the help guys!
 
I think you mean condenser. If it had a coil it wouldn't have a mag. The condensers I have seen are held in with one flat head screw. Then there is a wire to unhook.

Did you get your test light out to see where you are losing power?
 
The condenser does not have a wire, just a stud on the end. The coil, as you have found, is under the cap on top of the unit. Original coils (at least the really old ones) had a date printed on them. Unfortunately, without a coil tester there is not a whole lot you can do to check a coil. You can check resistance through both windings, but I can't tell you what a good reading is on an H-4 coil. Maybe someone else has some numbers.

The best test may just be to use it. Make sure your points and condenser are good, then see that you have a good spark and still have a good spark when it is hot from running it a while.

Follow this link to the IH magneto service manual. It may give you some useful information. The H-4 section startes on page 39.
http://www.cleancomputes.com/Cub/Bl...s/GSS-5035 Service Manual Magnetos/index.html
 
My bad, I worked on my neighbors VAC and I thought I remembered a short wire from the condenser.

Also sorry about the coil thing. I thought it was only a coil when it was the big round thing on top.
 
I was in fact talking about the condensor as shown
in illustration 77 on page 39. From what I read in
that manual it does not sound like I can test the
coil or the condensor without special equipment.

Anybody know of a good place to have one rebuilt?
 
That wire is attached to the stud on the condenser but is a part of the coil. Condensers are cheap. When they are suspect, people generally just swap in another. Coils usually become suspect if the spark is poor after the cheap fixes have been tried.
 
Thats a good point...I'll go ahead and order a tune-
up kit and see if that fixes the problem. Will
update in a few weeks with the results. Thanks
 
(quoted from post at 19:10:29 06/08/12) Thats a good point...I'll go ahead and order a tune-
up kit and see if that fixes the problem. Will
update in a few weeks with the results. Thanks
Click to expand...

TSC and Farm & Fleet carry them right on the shelf. I think both are Tisco, but F&F is for sure.
 
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