Any clever Foccers out there?

[unfazed]

If cylinder 3 is firing that really rules out the coil as cylinders 2 & 3 fire from the same coil and swapping the leads from 2 & 3 more or less rules out the plug caps. Check to see if they are tight on the leads anyhow.

Lift the tank and swap the wires on coils for 2&3 with the wires on coils 1&4 and then swap plug leads 1 with 2 and 3 with 4
If 2 still does not fire then the problem is to do with that cylinder or the number 2 carburettor

When you drained the fuel from the carburettor did you let it run with the pump feeding it as it could be a sticking float or float needle.
Put a clear plastic pipe onto the drain plug holes of carburettor 1 and 2 to compare them, run it up the side of the carburettor and tape them in place, petrol should level around the top of the float bowl with the ignition on the the kill switch set to on/run. If it goes above this it is sticking open and below, it sticking closed.
Start the engine and see what happens.

If all this appears ok you could have a stuck ring. Unlikely but possible if where it was stored was prone to dampness.

Do a check on the filter and path to 2nd carburettor