Ignition points fouling

[Will]

OK, this isn't even Lancia, so I'm posting it in misc, but I figured some of you older guys who had worked on hundreds of points ignitions might be able to help.

I have a Fairbanks-Morse magneto (similar to the Wix "snap box" type with the impulse coupling) and the points seem to be fouling like crazy.

I get about a half hour of run time and they are carboned up, the machine runs fine until I shut it off, then it won't start because of weak spark.

I can't get the points completely flat, I know they touch on one side first, the carbon seems to be in the middle. The points also arc (yellow) when they open.

Is this a condenser issue? A spark gap issue? I'm at a bit of a loss. Any/all help appreciated!

[Scott H]

Will,

I just saw this. The old way to remember how to tell which size condenser is pretty easy.

"If you are minus metal on the minus contact you need to minus capacitance."

To actually have this quite often means the condenser is no good. Most capacitors were sized too big and would be minus metal on the positive side of the points with a little peak formed on the negative side of the points. I remember a lot were in the 0.20 - 0.35 uf. I have never seen a spec for condensers. I had only heard the little rhyme from above and had experimented with it on my first car, a 240z.

Good Luck!

I can't believe I remembered this.

Scott

[Will]

Thanks Scott. The aforementioned troublemaker was on my trencher, replaced the entire magneto with an ebay special (solving the problem) and sold the trencher- next guy's problem now :)

When I posted I was in the middle of trying to get an irrigation system in and yeah, I'm pretty sure it was trhe condenser.

Thanks for the mnemonic- I'll commit that to memory.