Should the throttle needle be fixed down?

I have been cleaning my dellorto carb and noticed that the needle valve just drops down loose into the throttle slide piston into a hole in the middle. My last scooter had a clip to fix the needle into place but this one just seems to sit in place with nothing locking it down.
Obviously when i throttle up it draws the slide up and pulls the tapered needle out of the main jet venturi. When i decelerate and the piston lowers again, does the needle simply drop with it under gravity?
Whats to stop the needle from catching and not dropping down into the main jet hole again?
As i said, my last one was held by a clip so it had no choice but to move up and down with the throttle action.
Im having jetting issues which is why i am checking that this is correct.
Also, if i enlarge the main jet, should i change the needle size as well so it slots down better?

 

sounds like you are missing the plastic holder thing.... is it a pbgh?

 

Phva 17.5 mm but i expected a metal clip retainer of some kind to hold it down?

 

on mine, it goes needle, steel clip on the needle (mixture adjustment), plastic bung type thing, spring, carb cap. yours if i recall (speedfight?) should be needle, steel clip, a funny spring thats a kinda M shape, spring, carb cap...

 

Mm, thought so. I'm running a speedfight... Well remembered....and a gilra dna50. Its the dna carb thats missing the white plastic bung. Ive managed to finally find a youtube video of a stripdown and it looks like the one that you describe. Ive ordered a plastic bung from dellorto so i appreciate the reply. Another good result from putting out on this forum, thankyou.

 

im helpful most of the time..... ive stripped so many of those damn carbs i could do it with my eyes closed. when you put it back together, make sure to clean the little choke jets thing in the float bowl...

 

I saw that, tiny outlet right by the copper breather, just hiding away like a gremlin. I sprayed carb cleaner and a can of air through it so should be clear. Float gasket is my new pain. New story, different thread but as i dont put any gasket sealants near my carb its a cereal box gasket until i order a new rubber one.