Dellorto carb questions

[David Rubie <David.Rubie@domain.elided>]

Some more experienced Alfisti might be able to help me with this.

Long story short:  Trusty the Alfetta has a set of 45mm DHLA carbs
in place of the factory 40mm items, replaced by the previous owner.
He (fairly obviously) never really got them to work properly and neither
have I satisfactorily, although I made a recent breakthrough which shed
some light which I'll detail.

I bought a Dellorto factory book some time ago but hadn't bothered
opening it until recently.  I've been driving around for a couple of years
with a massive flat spot off idle (which can be ameliorated with careful
application of the throttle) but just how bad it is was demonstrated when
a friend of mine drove the car (with me in it) and nearly stalled at every
intersection.

When re-fitting the carbs last time, I had forgotten to adjust the
accelerator pumps.  In fact, they were totally loose and not
contributing anything.  Once I had this (sort of) sorted out
the big flat spot has *almost* gone, but I'm still left with a
directly off-idle stumble that I think is now fixable.  I'm
not discounting the possibility of vacuum leaks, as the
carb rubbers are well overdue for replacement.

Does anybody have any idea about the steps used to get
the progression right from idle to accelerator pump
actuation?  The Dellorto book and the Haynes manual
give conflicting advice about where the idle screws should
initially be set at (Haynes says 4 complete turns, Dellorto
say 2.5).  I'm not 100% sure that the stumble is from either
a too-rich mixture or too lean, although the occasional back-spit
suggests too lean.  If anybody has been through this before, can
you offer me a few tips?

Thanks in advance,
dave.
1978 Alfetta GTV "trusty"
1975 Alfa Spider Veloce "rusty"
1994 Volvo 850 T5 wagon

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