Magneto help

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Magneto help

Postby wilsonjosh3307 » Wed Feb 23, 2022 7:15 pm

Hey I have a 48 cub with a 6v pos. ground and magneto. When I got it it was a wiring mess and I need help. It has a magneto and a distributor coil that is parts # ABC011 in the Steiner book. My understanding is that with a magneto I do not need that separate distributor coil correct? Also will I need a voltage regulator? I took the distributor out and wired the switch to the magneto just to try it and the switch wire melted down. Is that due to needing a voltage regulator? I am new to 6v and magnetos and need some help and what all parts I need and the diagram to wire them. Thanks for any help

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Re: Magneto help

Postby k hutchins » Wed Feb 23, 2022 8:18 pm

The distributor coil was probably added because the internal coil of the magneto has failed. The internal coil is available to replace the bad one. I would suggest that if you are going to tear into the magneto that far, that you also replace points, condensor, rotor button and possibly cap.
The information you seek is probably redily avaiable in the How to archives here. After your 2nd post you should have full access to all parts of this site. Including manuals. Others will be along with more technical info soon l'm sure.
Welcome to the forum, enjoy your Cub and the experience of working on them.

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Re: Magneto help

Postby tmays » Wed Feb 23, 2022 8:37 pm

When the mag coil was switched over to the abc011 coil, the switch was changed to provide power to the abc011 coil. The post on a magneto is connected to ground via the switch normally. Making it a kill switch. Do not put voltage to the post on mag. So unless you changed the configuration of the switch, then you put the power to ground, this burning it up.
Voltage regulator is for charging battery. A magneto runs separate from the charging system. So you would need the regulator only for the charging system
Edit: you don’t need the abc011 coil if the internal coil of the mag is good. Highly doubtful that it is good since it was switched to external coil.

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Re: Magneto help

Postby staninlowerAL » Wed Feb 23, 2022 10:06 pm

Welcome to the forum. As previously stated the magneto manual that you need to explain everything that you need to know about the Cub J4 mag is BLUE RIBBON SERVICE MANUAL GSS1012. The first 4 or 5 pages are detailed instructions on service, maintenance, repair, etc. Also search this site for others experience and posts. Special tools are required to completely disassemble the internal parts and can be damaged if not done correctly. Best to seek someone who has had some experience. Mcdonald Carb and Ignition is a good source of parts.
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Re: Magneto help

Postby Rick Spivey » Thu Feb 24, 2022 8:23 am

As stated above, do NOT put power to the magneto post IF you are trying to run it on the internal coil as a proper magneto. Yours appears to have been modified to add an external coil, which was often a "fix" used when the internal coil died. The external coil is much cheaper and doesn't require opening the magneto to make this switch. Completely rebuilding a magneto will cost anywhere from $60 to $150, depending on which parts need to be replaced. If you've never been into a magneto, please read as much as possible, and go slowly. You can break things that are no longer produced if you don't understand how it's put together.
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Re: Magneto help

Postby Eugene » Thu Feb 24, 2022 8:27 pm

The magneto with an external coil will work quite well.

Suggest before working on the magneto as a magneto, understand how a battery powered ignition system works. Get the current system functioning first.
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Re: Magneto help

Postby Glen » Thu Feb 24, 2022 9:34 pm

Below is magneto info, if you need it.

The magneto is originally separate from battery power, it makes it's own power for the spark plugs.
There is no battery power connected to the magneto.

The ignition switch for the magneto has 1 post, for 1 wire going to the side of the magneto, the switch grounds the magneto to stop the engine, when in the off position.

The ignition switch for battery powered coils has 2 posts, 1 is connected to a power source, the other to the wire going to the coil.

If the magneto is using the original style of coil, they have said on here to not connect battery power to the post on the side of the magneto, it can damage the magneto.

Below are parts from TM Tractor, you can look at the pics and see what the magneto has.
TM Tractor is at the bottom of the page.
The 1st part is the magneto coil, it is under the cap on top of the coil.
There is a rectangular bar that goes through the center of the coil, if you buy a new coil, you need to save it and reuse it with the new coil.

The rotor is gear driven.

Below are listings for the ignition switches. These are the new switches that are sold, the original switches in the 1940's and 1950's were a different style.
TM Tractor has lower priced switches also, it says.

They have said on here to not turn the magneto drive coupling, and make the magneto snap, without somewhere for the spark to go.
It can damage the coil in the magneto to make it spark with no place for the spark to go.

When testing the spark, the spark has to be able to go to ground.
Put a spark plug wire in the coil post, and hold it by the insulation so the other end is about 1/4" from the metal of the magneto case, or if the magneto is on the engine, a bare metal place on the engine block.
The spark should be blue or white, not yellow. Yellow is weak and needs improving.

The insulation in the side of the magneto where the end of the points spring is can get old and crack, then the power can ground there.
Check it and be sure it is good.
Below is a new one, it gives a magneto serial number in the listing telling which magnetos it fits.
I think the serial number begins with J4.

Below is a pic of aligning the rotor and pinion timing marks.
Clean the area under the rotor cover and grease the rotor and pinion gears also. :)
Cub magneto 4.jpg
Cub magneto 4.jpg (25.13 KiB) Viewed 277 times

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Re: Magneto help

Postby wilsonjosh3307 » Sat Feb 26, 2022 10:05 pm

Thanks for all the good info. After looking it does have the voltage regulator on top of the generator I just couldn't see it with the hood. I have a guy I go to church with that is the local farmall expert who I will ask about rebuilding the magneto for me. I plan to take hood off tomorrow and tear into the wiring more thoroughly. It looks like it has had some half way work done to it previously that I don't like being there. Thanks for all the help guys this 6v and magneto is all brand new to me and still trying to fully comprehend it all

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Re: Magneto help

Postby Barnyard » Sat Feb 26, 2022 11:24 pm

Check this out. You are only an hour and a half from a great Cubfest where you can meet many of the members from this forum. It is a great place to learn more about your Cub.
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Re: Magneto help

Postby Glen » Sun Feb 27, 2022 6:07 pm

wilsonjosh3307 wrote: I am new to 6v and magnetos and need some help and what all parts I need and the diagram to wire them. Thanks for any help

The magneto wiring is 1 wire from the 1 post ignition switch, to the post on the side of the magneto, to ground the magneto, that stops the engine.

The part on top of the generator is originally a cutout, or Relay, IH called it.
It is not a voltage regulator. The Relay was used before the voltage regulator came out.
IH started using voltage regulators on Cubs during 1950, they are on a bracket beside the gen, not on top of it.
With the Relay, you have to choose the charging rate yourself, using the 4 position switch on the dash, if it is still there.
The 4 position switch controls the charge rate, and the lights.
It has 4 positions, L, low charge, H, high charge, D dim front lights, B bright lights.
The Cub owner's manual below tells how to use the switch beginning on page 34.

The Cub owner's manual can help you learn about maintenance that the Cub needs.

Below is the 1949 Cub owner's manual. The experts on here recommend people read it. It has lots of info about operation, maintenance, and lubrication. There is a table of contents on page 1.
It shows how Cubs originally looked in it. The lube section begins on page 14. ... index.html

It shows the electrical system that a 1949, and 1948 Cub originally had.
Cubs made before mid 1964 originally had 6 volt, positive ground electrical systems.
There is a pic with the hood off showing the electrical system on page 33 in the manual.

The 10 weight motor oil mentioned in the manual for the Touch Control was changed later to Case IH Hy-Tran fluid. It is sold at Case IH dealers.
There are other brands, be sure it works with IH hydraulic systems before buying one.
The manual tells how to check and change the Touch Control fluid, and remove the air from the system.
Be sure to check the fluid with the arms in the rear, or down position, the manual says.

I would check or change all the oils before using the Cub. Using it with low oil in a gear housing can damage the parts in the housing.
There are 3 separate gear housings, with 3 separate oil levels to check, in the rear area of a Cub, the transmission, and 2 final drives.

The transmissions in Cubs commonly get water in them, from rain, or condensation inside the housing over time.

The air cleaner is an oil bath air cleaner. Dirt that is sucked in settles to the bottom of the oil cup. It should have clean, light motor oil in the oil cup to work right.

There is a search box at the top of the page, to the right of the Farmall Cub, you can find info in posts that have been made.

Nowadays there are voltage regulators that are made to go on top of tractor generators.
IH didn't put them on Cubs, they are not shown in the Cub parts manual.
You should look and see if someone put 1 on your Cub, so you can wire the Cub correctly.
The original Relay has 3 posts for wires.
The voltage regulator probably has 4 posts for wires.

Below is a wiring diagram for the Cubs with a Relay.
The 2nd pic, from TM Tractor, shows the back of the 4 position switch. The fuse is for the lights. :)
Cub switch 3.jpg

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