The emulsion tube is seated once you feel resistance from the threads. Do not reef on those threads, they'll strip easily (if the zinc casting doesn't break first) then you'll be really unhappy. Only thing I've not seen, so far, is the emulsion tube...out of the carb. Hate to keep harping on this but, unless every one of those minuscule wall orifices is completely clean & flowing freely, it'll never deliver normal performance. If you're rodded them out, using a thin wire, then you're probably done with that cleaning chore. There's still a slight chance that one, or more, could remain partially clogged...ask me how I know this. OTOH, if you're relying on carb cleaner and a wire brush, the odds of success fall dramatically.