You could call all of the small engine repair shops and power equipment stores and ask about used parts or where to find them, or you could search ebay etc. for a place to start. If you knew anyone with the same engine family on their equipment you could try a parts swap; be sure to check the gap on the donor engine and reinstall the coil to the same gap when replacing it.
Toyota MDT in MO
Absolutely incorrect!
The voltage required for dielectric breakdown of any gas between the a pair of electrodes INCREASES as a function of pressure. A weak coil that will spark fine with the plug lying on the cylinder head may not be able to produce a spark AT ALL at normal engine compression. Back when coils were a lot more fragile than they have been for the past 30-odd years, that was a fairly common cause for a sudden "no-start" or a mystery misfire that would only show up at high manifold pressure (and consequently higher cylinder pressure.)
Its also 'exactly why we have pressure reglators on high-current gas dischcarge closing switches for pulsed power systems. Controlling the pressure in the switch controls how much voltage it will hold off before it self-triggers. I was a pulsed power engineer in a previous life (and still have all my fingers and toes, thank God...)
That's simple. just look up the dielectric strength of any common gas (air, for example) as a function of pressure.
It's a fairly well known fact. One of the reasons those long fluorescent bulbs bulbs can support an arc that is so long is because of the low pressure in side.
The fact that he has spark under normal atmosphere pressure doesn't mean it will fire under increased pressure of compression. The correct method to check if it will fire under compression is to widen the gap. The amount of voltage that the magneto can produce is proportional to the gap. On a lawn mower with relatively low compression the spark should be able to jump a gap of at least .1" to be considered good. although just having spark doesn't mean it is firing at the right moment.
-jim
The point of my post was the original poster had several more obvious and likely causes of the non-start problem to rule out before trying to fit an automotive coil to a lawn mower engine.
Why would anyone seriously consider doing that? Just asking...and marveling....
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As noted above: it was an _experiment_. I had some spark, but it looked weak. I wanted to see if it would run with a good spark. This was an idea to generate same.
George (OP)
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