16017 needle jets commonly fall out on their own, silently go missing....or sometimes stick in place, even when the emulsion tube is removed. There is no rule to determine whether one or both stay or go.
In any event, don't pound on them to remove, if they are stubborn, simply clean the inside diameter while its in place.
It IS, however, essential they be accounted for both during service and especially upon carb assembly.
Expensive little boogers, do not lose!
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