This one may be wrong, but since you have tried everything else....I had a similar situation with an optimus 111t silent burner. Just could not get it to not run yellow. Ended up taking the burner off and boiling it in citric acid and a brass brush...really clean it like bare metal. With a magnifying lens I saw hairline cracks under the bell where the 4 pipes connected. I had a few of them. Ended up having to try silver brazing for the first time in my life but that was exactly what was wrong with it. Cracks = too much fuel = soot and orange flames from the cap. It runs on anything now (kero, aviation fuel, white gas) and it blue as glacier water. I think you should get a jewelers loop or something with high magnification and look for cracks. I could not see mine without it. My thread is in the fettling forum and has a lot of photos of the cracks
