It should be smooth. Being jerky won’t affect it much but it will seize up sooner or later and that will cause problems. You might need to take it apart and grease it. The search function is your friend.
is it the valve itself that is jerky (i.e. when you take the cables off and turn by hand is it jerky) ? If so - probably have to remove, clean, and grease (as ciaran said). Or is it jerky when the servo moves it? if this is the problem then your cables may have to be greased as they may be causing the problem, or your servo motor could be struggling.
Good question - I didn't check which one was struggling. Is the servo at the other en of the cables kinda just to the left side of the seat?
When you say jerky... the EXUP servo does tend to move in a twitchy manner and that is normal. It's not simply a direct translation from throttle position or rpm, it's position will vary opening slightly at low rpm (~4k), then opening to approximately 60% by 9k, then fully open at 12k rpm (if i remember correctly). If there is resistance in the valve itself then it's wise to remove, clean and lube (check the service manual for the type of lube as it needs to be high temperature friendly). If the resistance isn't in the valve then i'd highly recommend lubing your cables thoroughly... else one of the cables is likely to snap soon.
