My wife's mower wouldn't restart when she stopped it for a few minutes. I determined that there was suddenly no spark (starting fluid, looked for spark with new plug). This is an extremely simple "ignition system", just a coil with flying-magnets on the flywheel and the spark plug. Yeah, there is a kill switch, but I disconnected it right at the coil, no joy. I checked continuity of the HV lead and the primary/secondary coils, all seemed good. I reluctantly bought a new coil ($40+!) and installed it. I still had no spark at a test plug with that, but started wondering if I was spinning the engine fast enough to see it (spinning with plug out and a speed-wrench on the crank/flywheel nut). Well, I "played along with it" and finished assembling and it fired on the first pull. So, my wife resumed using it and it died again after about 15 minutes. I got it to start again and watched it run briefly and sputter to death; no spark again. No visible spark, and no joy with the starting fluid. I am open to suggestions as to what to look for. Photos of the (old) coil are attached.
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