Make sure we're the voltage regulator mounts to the frame has a GOOD ground. No paint, no powder coat.
Harley voltage regulators shunt excessive voltage to the frame.

https://www.electricity-magnetism.or...age-regulator/

 

Recheck the ground on the Voltage regulator.
Chances are it's not good enough.

 

It's a new regulator.. I run a ground wire from the back of the regulator to ground.. I also check regulator to ground at various points through out the bike including to rocker cover bolts and clutch release cover bolts.. I have great continuity every where..

 

The is no such thing as shunting to the frame.. That is a single point.. Shunting requires 2 points.. What they do is shunt the output of the regulator.

The examples in that link are not what HD does. For one using a linear device dumps all the excess energy. This create an excessive amount of heat. Early English and Japanese bikes got away with it as they had marginal charing systems. Not a whole lot of power / current generated..

I believe that HD regulators use SCRs or Diacs to chop the output of the regulator.. @bustert has the schematics that are close.. The alternator is like a current source. Shorting the output dumps less power then trying to regulate it with a linear device and reference or Zener diode.

I've not seen regulators spike but I've seen them go high after some heat.. I would expect that loose component inside the device could cause spike tho.

 

I honestly don't think that two regulators could be the cause.. I'm getting identical results with both with nominal output of 14.3.
Maybe it's just something within the speedometer head, I'll hook up another voltage regulator to see what that shows...

 

I just skimmed through this quickly, so I'm sorry if I missed something, but I had a similar problem with an idiot shop on the road working on my FXRS. They had a Dyna ignition which required a 5 ohm coil instead of the usual 3 ohm for most Evo Big Twins. There were many other problems with their work, but when I got them sorted out at my home shop the bike ran fine for a short time and then just started backfiring and eventually would only run for a short time before it had to cool down before it would run again. They had sold me a new 3 ohm coil instead of the required 5 ohm. Just make sure you have the right coil.

 

mp, I know from another thread several months ago that he has a 3 ohm coil and it's an S&S - he posted a photo of it.

But that's good you brought it up because he's been thru many ignitions in a fairly short time and the only constant is the S&S coil.

Hotrod, easy as it is to change on that softail, why not put a stock coil on an run it on dual for for a while, see if the single fire coil is acting up.

 

I do have a spare Single fire coil . I'll give it a shot..

 

Just because you put 2 new VR's and had the same issue
don't rule that they are both bad.
Everything, especially electronic stuff these days is garbage.

 

Deleted..