318 Engine stumble

No matter how it happens;
If the polarity get's reversed on the pick-up, you will be able to time the engine at idle. But as soon as she starts building rpm, the spark will scatter willy nilly,with timing all over the place, and with no rhyme or reason to it, and the engine will run just horrible. You can easily see this with the timing light set to zero/ no advance compensation. I made my boss $1500C one time figuring that out. Longstory. Yes I have seen factory pick-ups coded wrong lol. And not just Honda motorcycles either.