Is my magneto bad?

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Idahocub
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Is my magneto bad?

Postby Idahocub » Wed May 29, 2024 3:17 pm

Running good then all of a sudden started running rough. Then died and can’t restart.
Have a j4 magneto. No battery or generator. Hand crank only.
Took the lead off the center of the distributor cab. Held it to the ground on the motor. No spark.
Tested the switch on/off continuity was good.
I have new point & condenser to install. But that’s after the magneto. I should have a spark prior to points, correct?

Eugene
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Re: Is my magneto bad?

Postby Eugene » Wed May 29, 2024 4:06 pm

Idahocub wrote:I have new point & condenser to install. But that’s after the magneto.
No, not really.
I should have a spark prior to points, correct?
Magnetism builds up prior to the points opening. Spark occurs when the points open, collapsing the magnetic field and also discharges the condenser.

First thing, remove the distributor cap and check the condition of the points.
I have an excuse. CRS.

Gary Dotson
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Re: Is my magneto bad?

Postby Gary Dotson » Thu May 30, 2024 8:00 am

Since the ignition switch, for the magneto, is a grounding (kill) switch, you can disconnect the wire from the side of the mag and check for spark again. You should have spark with it disconnected. Issues with the points is the leading cause for having no spark, I always look there first.

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SONNY
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Re: Is my magneto bad?

Postby SONNY » Thu May 30, 2024 12:51 pm

check the insulator thru the side of the mag for cracks too! They are bad for cracking/old age/getting oily/etc. and grounding out at that point.

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Re: Is my magneto bad?

Postby tst » Thu May 30, 2024 2:36 pm

coil does go bad also from old age so check it

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SONNY
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Re: Is my magneto bad?

Postby SONNY » Fri May 31, 2024 10:30 am

The problem I had with mags is the coils are always dead or go dead and thats why I convert to battery coils or dist.
Even with hand crank motors I use battery coils on the mags. Full charged battery will run several days before running down. Dad always changed the balers, combines, and tractors that way. Always worked good.


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