Doesn't the jet have a screw slot in the end? Just to be clear, theres a tube extending into the float bowl and at the end is the main jet.. (#1 on that exploded view of the carb)
every jet i ever saw was screwed in.. when you put it back in, screw it in snug and then just a tiny bit more.. don't crank down on it... i think they are soft brass..
why are you taking that jet out? are you just cleaning things or did you already do a lean/rich test at top speed?