1935 JD magneto

Loftfield · Sep 2, 2015

Magneto on JD B (Brass tag #6568) has no spark at points. How do I check mag, coil? WICO mag #AP 1778 Ser No. 041442. I am new to JD-B, but have restored many Model T Fords and other mag tractors. Any help is greatly appreciated.

tractorguy2 · Sep 2, 2015

You shouldn't have spark at the points. Sparking points
mean they are dirty or the condenser is bad.

Test it by holding one of the spark plug wires about 1/4
away from the base while turning the drive with a pair of
vise grips.

When the impulse snaps. Spark should jump from the wire to
the base.

old · Sep 2, 2015

Being that fact it is a mag you can not check the point by looking for a spark when they open up. On those you have to have the cap on to check for spark. Clean the points real good put the cap on and then check for spark at to plug wires. You need to have a good blue/white spark that jumps a 1/4 inch gap or more. Plus you need a good working impulse tripping or it will not fire as it should also. When you turn the engine over you should hear the impulse trip if you do not then that could be the problem also.
I too own a 1935 JD-B and even have the owns manual that came with it when it was new.

John T · Sep 3, 2015

Sure, its POSSIBLE for coils or condensors to go bad HOWEVER a typical casue of no fire is the points are burned or pitted or not gapped correct. First thing I would try is to non abrasively as possible clean/buff/polish the points to see if that works. If they are badly burned or pitted using a points file to dress them may make her work, but if that bad Id get a new set. Of course, if the springs wind and trip impulse assembly isn't working (may be stuck from rust or dirt) making no loud sharp SNAP noise, she wont fire at cranking speeds although it may be possible to pull start it.

John T

1935 JD magneto

Loftfield

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tractorguy2

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old

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John T

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