FMJ Magneto, spark plug wires

BIGR · May 4, 2013

I have a '37 WC that ran last fall. Was in closed storage for the winter, I got in my head to put new plugs and wires in it over the winter.
Went to start it, and no spark. The wires I put on it were stranded metallic instead of solid core. My friend said I probably screwed up the mag by putting on the stranded wires and trying to crank it. Of course, I threw the old wires away. Any ideas? Any sources for solid core wires?
I got the stranded ones from Napa.
Again, ran good last fall.

old · May 4, 2013

Stranded wires are correct and no plug wire is a solid type single stand wire for plugs because the vibration would sooner or later make them break. Your problem is more then likely to be that the points have corroded from sitting over the winter and need to be cleaned or replaced. By the way if you need a manual for that mag just send me an e-mail and I'll send you the copy I have in this computer

John T · May 5, 2013

I suspect your friend may be confusing carbon core suppressor wires (NOT best thing for Magneto Ignition) with stranded wire core (better for Mag Ignitions) plug wires.

Still even if it had carbon core suppressor wires that alone dont stop her from firing.

Even oxidation on point surfaces can prevent a mag from firing, let alone carbon and burns and pits (much worse). Id non abrasively as possible try to clean/buff/polish the points n check the gap and try her. You could even drag a dollar bill (a $20 may do better lol) between the surfaces n see what happens. For carbon or pitting a points file may be more in order, but once you over file them a lot they dont last long.

Of course, she cant fire at low cranking speed unless the spring wind n trip impulse assembly is working, although they can still pull start n run if thats the case.

John T

bjb in TX from Ne · May 7, 2013

John T,

I have been meaning to ask, why are the carbon cores bad for a magneto system. I bought a set for my WC from Napa not knowing they were carbon core until I cut them to length. It usually starts right up when hand cranking (if i put enough gas in the tank). Will I ruin my mag if I run the carbon core wires? I normally only run it for about an hour when I am home in the summer.

Ted in NE-OH · May 8, 2013

Carbon fiber wires have a high enough resistance that won't load the magneto enough. This allows the output voltage to rise too high and may cause the coil to break down or arc.

FMJ Magneto, spark plug wires

BIGR

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old

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John T

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bjb in TX from Ne

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Ted in NE-OH

Well-known Member

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