The emulsifier looks good, Paul.
As for the jet, I'll tell one of my interminable stories to set the scene for the next step. About 15 years ago I had the job of working on a couple of very old high performance cars. One had been rebuilt and ran badly, the other was in pieces. Neither had the original carburetor, which could not even be described, the cars were so old. The previous tenant had tried to get the engine running by modifying a completely different carburetor (from a Tiger Moth engine). My approach to making it run was check that the ignition, compression and valve timing were right, and then blame the mixture strength. It was misfiring too much for things like spark plug colour to make any sense. So, I drilled out the main jet in steps, finding it ran better with each enlargement. Finally, with the jet 0.120", it ran properly (it was originally 0.080"). The trouble was with that huge jet diameter, it wasn't vaporising the fuel, it was just spraying liquid like a fire hose, so in cold weather it went back to running badly. A colleague pointed out that when you need a huge jet, that means there isn't enough "venturi vacuum" generated in the carburetor, so we needed to try a smaller venturi in the same carburetor. The colleague turned up a smaller venturi, and I soldered up the jet and started again, with the result that it ended up running properly with the jet at 0.080". At that point it was vaporising the fuel properly too, so it ran in hot or cold weather. A bit of research revealed that the previous tenant had thrown out the Tiger Moth venturi and made his own, much larger one.
The moral of this story is that there is no great difficulty in enlarging the jet step by step, and observing whether it runs better. The modification is easily reversed by soldering up the jet and drilling a new hole through the solder. Furthermore even your enlarged 1.2 mm jet is only 0.047", which is not a large jet, so you aren't coming to the end of the road with drilling it out in steps. The issue is, unless there is something wrong somewhere, the right sized jet should be somewhere near the original size, and it obviously isn't going to come out that way.
What I would do, is enlarge that spare jet further, until it stops running better each time you enlarge it. Then we can see how well it is running, and whether we can find an explanation of why it needed the bigger jet.
