Martin: I futzed around with my Dellorto 40's for Years before I finally threw in the towel and sent them to a professional at Blackline Racing here in the states.
When they went out to them, this is what I had installed for jetting:
These carburetors come stock with:
60 idle jets
140 Main jets,
180 air correction jets,
35 accelerator pump jets and
34mm venturiis.
I had drilled the Mains out to 162.5 (happens to be a drill size) to overcome transition hesitation, which never went away.
This is what they had when I got them back from the rebuild, set up to my engine specs by Dave Hogland at Blackline Racing in Utah, who set them up on a flow bench and then tested them on a 1915cc engine (mine is a 2,110).
The jet sizes are:
.45 idles
1.30 mains
160 air correctors (to slow down the fuel through the main jets to overcome hesitation)
.35 Accelerator pump jets
32mm Venturis
E-Tube = #2
They are now so smooth they feel like fuel injection. I love 'em.