2-stroke carb question

[florida derbi rocket]

If I say this is about a Dellorto..nobody answers...Sooooo...here goes. I received spare carb parts with a carb I bought. The round cylinder that holds the needle has a # on it. #30. I have a slightly longer one marked #40...What is the reason for the choice?, and which is better? I thought the only adjustment was moving the clip on the needle? This is a new one on me.

[Zuma-Zuma]

You can change slide sizes, needle clip positions, you can change the needle and nozzle to different sizes. I'm not a Del'Orto man, so I can't say what it means in delorto. But if you look on the mikuni websites, they will explain what it means in mikuni. My guess is the difference will be in the midrange. Since WOT is the same with any slide, the cut-out portion may affect midrange velocity. It may also accept a wider range of needle choices. But these are guesses.