Electrical can be "fun", in the same way being scratched up by a mass of cats then dumped in a bath of lemon juice is "fun", or cleaning the carpet after said cats ate something they shouldn't have is "fun"! At least it's not intermittent, that's the most kind of electrical fun...
Did you try squirting some starter fluid into the air intake (after removing the filter) while cranking? (or the carb bodies if the boots are off)? Any life? (Something like
https://www.amazon.com/STA-BIL-2200...ref=zg_bs_15719711_sccl_1/138-2492783-5258346)
You need 3 things for a bike to run, correct fuel/air mix (within a reasonable range), enough compression, and ignition within time. Something common to both cylinders has failed, which is either kill switch (as that's the cut off for the 12v power to both), the crank sensor, or fuel. Unless it was already only running on one cylinder, it's pretty rare to knock out both cylinders at the same time on a running bike, and has to be something common to both. I've had my Shadows run with a carb down and run with the electrical to a cylinder down, still easily producing enough power to haul my a$s.
With the key ON and the kill switch in the RUN position, do you have 12v on the black/white connector on the coils?
Can you get an inline ignition tester like this HF :
In-Line Spark Checker? I have the same type myself and while they cannot tell if timing is working, they CAN tell if you have spark. If you have dual-plug head you MUST have the other plug connected for this, as the path of the current goes from the coil to the first plug, through the first plug to the 2nd plug, then returns through the 2nd plug to the coil. These things light up quite nicely if you have spark, even a weak one.
If there's still no life but you have spark on at least one cylinder, we also need to check you haven't got a fuel blockage. Open the drain screws on each carb, see if you get any fuel out. Also check the quality of the fuel, in case you've somehow got water in the bottom of your tank. Does what comes out seem more like gas or water?
You mentioned on the 16th that you had good spark from the coils (at least as I read your post), but I cannot see fuel being checked.
You mentioned the fuel cut-off relay not being connected, and I wonder if the fuel pump is getting power?
I have seen fuel problems seem more like electrical, and vice-versa.
The other thing to do is check compression if fuel and spark seem OK. But that should only kill one cylinder, unless one was already down. Considering one of your cylinders is nearly the CC of my whole bike, you might not've noticed one dead pot. And one of my cylinders is well below "working range" yet she runs fine.
An '86 1100 is one of the models I'd kill for
. Don't give up, you'll enjoy this bike once you get past the PO's "work". My bike still has bits that I'm scared to touch, and while she runs I ain't gonna. A 750 (86), but a pleasure to ride still despite all the miles I've done on her.