Magneto Problems

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Owen
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Joined: Fri Jan 08, 2021 1:34 pm
Zip Code: 13060
Tractors Owned: 1949 Farmall Cub (Cletus)

Magneto Problems

Postby Owen » Fri Feb 04, 2022 11:38 am

I bought my ‘49 cub three years ago. Last winter I did an engine “overhaul”. Last summer I started getting issues. Whenever it rained the tractor would get hard to start. Eventually it wouldn’t start at all. My grandfather and I pushed it in the barn and it has sat ever since. After multiple unsuccessful attempts at starting the tractor I decided to see if I had spark. I was unsuccessful so I decide to take off the magneto. When I opened up the magneto there was at least 3/4” of water. I bought a new coil, points, condenser, and gasket set and I still don’t get any spark. Is there anything I’m overlooking? Any help would be appreciated.

69ranger
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Tractors Owned: 1948 Cub, 1952 Cub, 1953 Cub, 1946 Farmall A, 1949 Farmall M, 1956 IH 130, 1979 IH 140, 1959 Farmall 240.
Several Brand X Green tractors that sound strange when they run.
1969 F-100 fully restored, 1969 F 100 original paint, 1973 F 100, 50 K original miles all original, 1978 F250 repainted, 1978 Bronco, 1967 Mustang, 1973 Mach ! Mustang.
Several single cylinder Honda motorcycles from the early 70's. Adding more junk all the time.
Location: Parsons, Kansas

Re: Magneto Problems

Postby 69ranger » Fri Feb 04, 2022 12:21 pm

Welcome to the forum.
If the magneto is still on the tractor remove the kill wire, to eliminate that, as the switch will some times fail.

Magnetos are not that difficult to work on, but that said everything must be correct, and nothing grounded out that not supposed to be, for them to work correctly.
Water is the mortal enemy of any ignition system, or electronics of any kind. Aside for the obvious problems with rust and corrosion it can also cause the spark to go to ground easier, and weaken or kill your spark.

So is everything clean and free of water now? If yes, then what are the conditions of the inside of the magneto? Things need to be clean in there, and all connections free from corrosion. If there has been water in it, what does the impulse spring look like? Working?
Are you points set to .015? You are on the right track replacing the coil as most of them have not been replaced and the are approaching 75 years old now. When you replaced the points and condenser did you make sure the wires did not get against the case?
Did you time the gears up when you put it back together?

There is a couple of pretty good videos on You tube that cover Cub mags. Watching these can shed a lot of light on how these work and help you repair yours. There is one that a young lady does that gets pretty in depth and show the mag taken completely apart.

Take a look at what the video shows, and check a few of these things out, and let us know how you come out.

Good luck with your project.
Last edited by 69ranger on Fri Feb 04, 2022 10:29 pm, edited 1 time in total.

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Mike in Louisiana
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Re: Magneto Problems

Postby Mike in Louisiana » Fri Feb 04, 2022 12:25 pm

Did you line up the timing marks on the gears. Someone else with more knowledge on mags will probably chime in.
You can also search on here, how to time magneto
1975 cub (LouAnn) serial # 245946, 1941 John Deere Model H

Good judgment comes from experience,
and a lot of that comes from bad judgment. Will Rogers

Eugene
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Re: Magneto Problems

Postby Eugene » Fri Feb 04, 2022 12:31 pm

69ranger wrote:Are you points set to .015?
.013.

Edit: You can drive the magneto with an electric drill and correct socket. Place magneto in a vice, plug wire and spark plug with the spark plug grounded to the vise.

Check the magneto rotation before using the drill. You may have to back up the magneto rotation before the impulse coupling to get it started.

What I'm suggesting is that you can work on and test the magneto on the bench.
Last edited by Eugene on Fri Feb 04, 2022 12:57 pm, edited 1 time in total.
I have an excuse. CRS.

staninlowerAL
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Tractors Owned: Cubs: (3)'49's, (1 is parts), (1)'57 IH Cub LoBoy w/FH, (2)154 Number Series Loboys, (1 is parts), '76 Longstripe w/FH, Mowers: C-22, Bush Hog 412, Pennington 59, Woods RM42CF, Woods 42, assorted FCub plows, planters, discs, etc. OTHERS: '49 AC B & Ind. Sickle mower, '61 AC D12 Ser 2, '52 8N, '56 Ferguson 35 Deluxe, '47 & '49 Avery V, '53 MM BG (offset), '51 JD M (regular), '56 JD 420C, with Blade and fire plow, '85 JD 850 (Yanmar) w/72" belly mower, '76? Yanmar 2TR15 1500 & Bush Hog SQ42S-2 mower, '78? FORD Dexta, '86 FORD LGT14D & 48" Mower, (3)Cub Cadets & Mowers (MTD), (4) Sears Surburban's, other MTD mowers, Jeeps & other misc. "treasures"
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Re: Magneto Problems

Postby staninlowerAL » Fri Feb 04, 2022 12:39 pm

Magneto coil replacement requires critical sequential steps to be followed, which have been covered by other posts on this forum, try a search for the topic at the top right corner of this page. Also check the HOW TO subform for information. Some things to be careful to observe are timing which the coil replacement process should begin with the engine at TDC on the compression stroke. Once this position is achieved, do not move the crankshaft again until all repairs are made to preserve the "in time" position. The points can be replaced and gap set and rotor and pinion gear must be installed with the timing marks correctly aligned. The spark advance should also be checked and serviced while you are making repairs. It's possible that one or both of the springs might need replacing. This requires a special tool to remove the parts necessary to check and repair/replace them. One more post and you can access/download the manuals at the Quicklinks tab (top left corner of this page). Look for GSS1012 Electrical Equipment, the first 5 pages give detailed instructions on cleaning, lubrication, maintenance and repair of the J4 magneto. Good luck with your project. Stan

tst
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Re: Magneto Problems

Postby tst » Fri Feb 04, 2022 12:47 pm

as mentioned did you install it correctly for timing, did you set the points to .013 ? did you rotate it off the tractor to see if it snaps ?, if all those are ok maybe a bad coil

Owen
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Joined: Fri Jan 08, 2021 1:34 pm
Zip Code: 13060
Tractors Owned: 1949 Farmall Cub (Cletus)

Re: Magneto Problems

Postby Owen » Fri Feb 04, 2022 1:27 pm

Thanks for all the replies. The points are set at .013. I would have timed the gears up again but the gear is so worn that there no longer a mark. I will check for more things tomorrow.

tst
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Re: Magneto Problems

Postby tst » Fri Feb 04, 2022 1:29 pm

the marks are on the rotor and top of the gear, no wear at those spots, look in the manual and it will show that

staninlowerAL
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Posts: 4260
Joined: Fri Oct 29, 2010 11:34 pm
Zip Code: 36558
Tractors Owned: Cubs: (3)'49's, (1 is parts), (1)'57 IH Cub LoBoy w/FH, (2)154 Number Series Loboys, (1 is parts), '76 Longstripe w/FH, Mowers: C-22, Bush Hog 412, Pennington 59, Woods RM42CF, Woods 42, assorted FCub plows, planters, discs, etc. OTHERS: '49 AC B & Ind. Sickle mower, '61 AC D12 Ser 2, '52 8N, '56 Ferguson 35 Deluxe, '47 & '49 Avery V, '53 MM BG (offset), '51 JD M (regular), '56 JD 420C, with Blade and fire plow, '85 JD 850 (Yanmar) w/72" belly mower, '76? Yanmar 2TR15 1500 & Bush Hog SQ42S-2 mower, '78? FORD Dexta, '86 FORD LGT14D & 48" Mower, (3)Cub Cadets & Mowers (MTD), (4) Sears Surburban's, other MTD mowers, Jeeps & other misc. "treasures"
Circle of Safety: Y
Location: AL (Southwest)

Re: Magneto Problems

Postby staninlowerAL » Fri Feb 04, 2022 3:38 pm

tst wrote:the marks are on the rotor and top of the gear, no wear at those spots, look in the manual and it will show that

Excessive wear on the rotor and pinion gear will also affect the timing.

Eugene
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Re: Magneto Problems

Postby Eugene » Fri Feb 04, 2022 5:56 pm

We have a no spark situation.

Check to see that the terminal on the side of the magneto is not grounded out to the case. Grounding the terminal kills the spark.

Go back through the magneto - disassemble and check for grounds and that it's internally wired correctly.
I have an excuse. CRS.

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Glen
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Re: Magneto Problems

Postby Glen » Fri Feb 04, 2022 7:18 pm

Hi,
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 to make it spark with no place for the spark to go.

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.

Below are listings for a new rotor, and pinion gear at TM Tractor, if you need new ones.

http://www.tmtractor.com/new/el/294fp.htm

http://www.tmtractor.com/new/el/615fp.htm

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.

http://www.tmtractor.com/new/el/957fp.htm

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. :)
Attachments
Cub magneto 4.jpg
Cub magneto 4.jpg (25.13 KiB) Viewed 292 times

Magnum
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Re: Magneto Problems

Postby Magnum » Fri Feb 04, 2022 8:51 pm

Any luck on this yet ? I'm curious to see if it was the kill switch .

Jim Becker
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Re: Magneto Problems

Postby Jim Becker » Fri Feb 04, 2022 10:30 pm

69ranger wrote:. . . There is a couple of pretty good videos on You tube that cover Cub mags. . . . There is one that a young lady does that gets pretty in depth and show the mag taken completely apart. . . .

If it is by the young lady I have in mind, I would encourage you to look at something (anything) else.

Bob McCarty
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Re: Magneto Problems

Postby Bob McCarty » Fri Feb 04, 2022 11:02 pm

Jim Becker wrote:If it is by the young lady I have in mind, I would encourage you to look at something (anything) else.

:Dito: Especially if it's the one on the carb rebuild!!!
"We don't need to think more,
we need to think differently."
-Albert Einstein

69ranger
5+ Years
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Posts: 185
Joined: Sun Jan 20, 2013 10:36 pm
Zip Code: 67357
Tractors Owned: 1948 Cub, 1952 Cub, 1953 Cub, 1946 Farmall A, 1949 Farmall M, 1956 IH 130, 1979 IH 140, 1959 Farmall 240.
Several Brand X Green tractors that sound strange when they run.
1969 F-100 fully restored, 1969 F 100 original paint, 1973 F 100, 50 K original miles all original, 1978 F250 repainted, 1978 Bronco, 1967 Mustang, 1973 Mach ! Mustang.
Several single cylinder Honda motorcycles from the early 70's. Adding more junk all the time.
Location: Parsons, Kansas

Re: Magneto Problems

Postby 69ranger » Fri Feb 04, 2022 11:19 pm

I agree, that her methods are not perfect I'm not saying that I would follow her on everything, but it shows some one that has never worked on one where everything goes, and how it comes apart.
There was a fellow who had some classes at one of the shows I attended. Its been 10 or so years ago, and I cant remember if it was at red power or at cub-o-rama? He put on a good presentation, and since I knew nothing, about mags then, I learned a lot.

I have a set of manuals that came out of an old time mechanics shop. They worked on magnetos, and about everything at one time in that shop.
When the shop closed I was able to buy a few things. The owner, who is still alive and active at 95 years of age, was extremely skilled at many things, and probably forgot more than I will ever know.
So far so good on what I have worked on.

I am anxious to see it the O P has figured out anything on this Mag yet?


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