It seems the guy before me put the wrong coils on this. One is 3.1 ohms and the other 4.1 ohms. Both are marked 12 volts. Maybe different brands and thus the slight different in ohm readings?
I hooked them up to a 12.6 volt battery as it came wired (in series). Total amp draw is 1.9. Voltage at one coil is 5 volts and voltage at the other is 6.9 volts. Note this is at a battery voltage of 12.6 volts. So I assume when voltage drops to 9-10 volts at cranking, those coils will only be getting 3.75 to 5.1 volts. I assume that means poor spark at cranking as wired.
This what Harley calls a "dual fire" system, but with four plugs instead of two. With breaker-point ignition Harley calls for a 4 ohm coil (more or less). I don't think there is any cost-effective way to make this 1968 a single-fire ignition. At least not with a cost within reason. Bikes a few years newer, yes.
If I could buy a pair of 1.5 ohm coils at a reasonable cost - I would go that route and hook in series. Since I have not found any at what I regard as a reasonable cost - I will try to use the ones I have. I am going to hook both in parallel so they have full battery voltage at cranking. I need to rig up something that makes the power to the primaries run through a ballast resistor once the engine is running. A simple switch would work, but that means I have to remember to use it. I am tempted to install a starter relay that has a built-in resistor bypass.
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