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Wico C Magneto

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Mark Poss

08-04-2013 16:31:24

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I have a 1939 JD H with a wico C mag. I am getting good spark on the flywheel side and weak spark on the pulley side. I just replaced the coil and rotor cap recently. It will not start hand cranking but will fire right up when pulled. Could the problem be a weak impulse spring? Any help is appreciated. Thanks, Mark.

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John T

08-05-2013 05:12:35

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Re: Wico C Magneto in reply to Mark Poss, 08-04-2013 16:31:24

The SAME set of points and coil fire BOTH sides, so if ones stronger then the other things Id suspect are;

Cap problems like a crack or carbon trace or the inner contacts..... .

Plugs or plug wires, swap them side to side to see if that fixes the problem.....i.e. is it still ONLY that one side regardless of plug or wire???

Insure on BOTH high cam lobes the points gap is the same due to a worn bushing or shaft problem maybe causing wobble. If so, sometimes a wider point gap is a band aid fix..... ..

A weak impulse spark but still a strong running spark (cant hand start but pull starts easy) can be a sign of a weak impulse spring or other impulse assembly problems.

It should yield a loud sharp SNAP each 180 not a faint thin wimpy dull clunk. Look for a deep visible blue spark not a faint thin wimpy yellow.

The start impulse timing needs to be right at TDC for good starting ID CHECK THAT and the points gap on both lobes

John T

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Mike M

08-05-2013 07:28:00

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Re: Wico C Magneto in reply to John T, 08-05-2013 05:12:35

Not uncommon to see a stronger spark on one side then the other. You can usually see this while testing one right at the coil without the cap or rotor installed. Don't know if it is due to a weaker pole on the magnet,worn lobes or other parts or a combination of all the above ?

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John T

08-05-2013 08:10:48

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Re: Wico C Magneto in reply to Mike M, 08-05-2013 07:28:00

One reason is the polarity changes each spark, one fires electrode to ground strap the other ground strap to electrode as the rotor magnet is obviously a North and South

John T

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Paul from MI

08-04-2013 20:05:07

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Re: Wico C Magneto in reply to Mark Poss, 08-04-2013 16:31:24

Common problem on Wico C mags is worn armature bushings. I'd check to be sure that's not your problem.

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Mark Poss

08-04-2013 18:39:42

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Re: Wico C Magneto in reply to Mark Poss, 08-04-2013 16:31:24

When hand cranking the mag impulse seems to have a good snap to it.

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D-

08-04-2013 17:41:28

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Re: Wico C Magneto in reply to Mark Poss, 08-04-2013 16:31:24

Do you hear the popping/clicking while hand cranking?

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husker44a

08-04-2013 16:39:24

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Re: Wico C Magneto in reply to Mark Poss, 08-04-2013 16:31:24

If it will start pulling it but will not start by the flywheel. Yes, replace the impulse spring. Might even get her a good tune up with new plugs,wires, points and condensor.

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