Are you sure it is the two needle carb??? That is a very old Sirio carb which had a lot of problems to tune it correctly, and that is why they changed to the 3 needle carbs of late Sirios.
Any way, Sirio recommends the following base settings:
HSN needle 5.5 turns out
LSN needle 3.75 turns out (should be flush with the end of the slide body)
Mid Range Needle flush with carb body, than 1 turn out
Glow Plug Novarossi C7TGF
Sirios need a lot of fuel, they don't perform well if you lean them to much.
If you really have that 2 needle carb, better be thinking on changing it for a Nova based carb, or the new Sirio carb.
Hope this helps
AFM