The jet moves down when the choke is engaged (it's not really a choke at all, but a means of enriching the mixture for cold starting) If it doesn't slide freely up and down it can stick in the "choke" position, or part way back up, giving an overly rich mixture in the relevant two cylinders.

With the choke linkage disconnected you should be able to move the jet easily by hand. Be careful when working with them as the plastic body is likely to be brittle.