Well, I got back to this again. What the link Nickb2 posted reminded me of was an "inconvenient truth" I am prone to ignoring: magneto systems have not only the flying-magnets and coil, but must have some sort of "breaker-point" arrangement. I don't understand how that works with a mag system, so tend to ignore the need to interrupt the coil primary. I kid myself that the primary is only used as a means to kill the engine, by shorting it out. The coil on this engine is the "integral" type, with the primary triggering module buried in the coil. Alas, B&S calls this system "Magnetron". If you search for that term you have to wade through quite a bit related to microwave oven magnetron tubes... Previously, when I thought there was only the plug, coil, and magnets, I had replaced both the coil and plug and was thinking the problem must be bad magnets, as unlikely as that seemed. I even toyed with the idea of trying to charge the magnets. Now though, I am reminded that the electronic triggering in the coil assembly could also be bad. In fact, reading resistance across the primary (on both old and new coil) shows that same low resistance now matter which polarity I use for the meter leads; as if they were just simple windings. I would expect that resistance would be different depending on polarity, since there is some active electronics in there. Worse yet, sometimes the new coil does show a difference, like ~1 ohm vs. hundreds of ohms, but it is frustratingly inconsistent. Can that be possible, or is there something flaky about how I am connecting the meter? Oh, wait, that is how the engine is acting, intermittent... Could it really be I bought a bad coil? I got it from a long-established B&S dealer, but that may not mean anything. They won't allow me to return any electrical parts, because any damage I do to them won't be visible. But, I bet that policy doesn't apply to their service techs as they "throw parts" at a problem in the shop. I would like to prove conclusively what is going on here, even if just for my own peace-of- mind. (Mowers are too inexpensive to make this effort practical!) I'm thinking now of opening up the old coil to repair/modify the interrupter circuit and prove the magnets and coils are OK. Anybody have good info on what is actually inside those coil assemblies?