Basically, what Rick Fisk said, Mike.
Is your Weber (kit) specifically set up (calibrated) for your motor?
Or, to put it another way....
is your motor in the same config. (state of
tune) as the carb. kit which is meant to serve it?
As otherwise, carb. calibration will normally require "tailering" and almost
always in
terms of the accelerator pump "shot" by
either quantity, quality or rate to avoid
an off-idle flat spot ("bog") when the foot goes well down quickly.
Another thing, in terms of sudden WOT,
variable choke SU's are very user friendly
when it comes to engines down a bit on
compression (vacuum). Fixed-choke carbs. like Webers are not, and most
especially so if the timing is a bit advanced.
Yet, another thing is most Spridget 948 or 1098 set-ups run 4.5 aux venturis.
1275's can run the same but some kits feature a 3.5 size which brings the main
system in sooner, the difference being most apparent
upon sudden, WOT (or nearly so) acceleration below 2.5k rpm or so. The
difference can help "cover" for an accelerator pump "shot" that's not quite
"right" for the specific motor, in terms of
an off-idle "bog" or flat spot when the foot
goes down quickly.
Anyway....let's start with the kit. Is it "proper" for the motor to begin with.
For
back when there used to be two kits out
there. One for a tuned Mini-Cooper S and
another for the stock 1275 Spridget. The
former comes with (among other things)
38mm chokes, the latter with "34"'s.
Put the latter on a stock Series A 1275 and
it will "mimic" exactly the symptom you are
experiencing.
Cap'n Bob
Basic Frog
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