Runing Rich at idle or lean at mid range

[Pete Gant]

Carburettors have been fully reconditioned on 1973 V12 with new jets (correct size) set 1.4mm (0.055?) below the bridge. Needles where fine and not replaced. I am having trouble tuning the Carburettors. The car has no emission control and the temperature sensors have been made inoperative by winding the nut right in. The problem is I can adjust the mixture to get it right at idle but then it is to lean at mid range, when I get it adjusted at mid range correctly it is to rich at idle. I do not appear to have any vacuum leaks.
I have in other posts asked about the depth of the jets below the bridge and there seems to be a nominal figure of around 2.54mm (0.100?)
Should I be resetting the jets deeper from the bridge towards 2.54mm? Does the adjustable needle not do a similar action or is it a combination of the jet being closer to the fuel at 2.54 mm below the bridge that the adjustment of the needle then produces different results. Or is there something else I should be looking at.

[D COUPE]

My understanding is rich at idle (7 or 8 %) and they will weaken off as the revs build.

Just some info I was given when setting mine up.............

Or if Your eyes water when Your stood at the back thats about right!!!!
(The carb mans words not mine)

[Woolfi]

Just an idea:
Check the synchronisation of the carbs. Maybe there is a "mismatch", with a result , that one or two carbs are running to lean at midrange.
Regards Wolfgang Gatza

[Doddsy333]

Peter, how did you set your jets to 1.4mm below the bridge. Did this require a special tool? I have rebuilt mine but am yet to try to tune the engine.