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1950 j4 magneto - distributor problem - need you help

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Hobbeslog
5+ Years
5+ Years
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Joined: Thu Jan 08, 2015 7:27 pm
Zip Code: 15853
Tractors Owned: 1950 Farmall Cub "demo"
1952 Farmall Cub
1958 Farmall Super A

1950 j4 magneto - distributor problem - need you help

Postby Hobbeslog » Thu Jan 08, 2015 10:52 pm

I have a 1950 Farmall cub with a J4 Magneto. I took off the distributor cap to get to the points. I had to turn the motor to get to a screw but I noticed something that
might be the cause of it not starting. When I turned the hand crank, to rotor didn't turn smooth, it would stay in one spot and then suddenly jump ahead. Is there an issue
with the mag or distributor?
Thanks for any advise.
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John *.?-!.* cub owner
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Re: 1950 j4 magneto - distributor problem - need you help

Postby John *.?-!.* cub owner » Thu Jan 08, 2015 11:15 pm

That is normal operation at cranking speed. The impulse hits a stop and compresses a spring until it reaches a certain point, then it releases and gives the shaft a quick spin to provide the energy to fire the magneto.
If you are not part of the solution,
you are part of the problem!!!
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Eugene
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Re: 1950 j4 magneto - distributor problem - need you help

Postby Eugene » Fri Jan 09, 2015 12:00 am

Normal. Called the impulse coupling.

The magneto has two firing positions, impulse coupling which retards the spark to TDC at engine cranking speed and full advance, 13 degrees with engine above 250 rpms.
I have an excuse. CRS.
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Hobbeslog
5+ Years
5+ Years
Posts: 3
Joined: Thu Jan 08, 2015 7:27 pm
Zip Code: 15853
Tractors Owned: 1950 Farmall Cub "demo"
1952 Farmall Cub
1958 Farmall Super A

Re: 1950 j4 magneto - distributor problem - need you help

Postby Hobbeslog » Fri Jan 09, 2015 12:12 am

Thx for the information. Much appreciated.
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