You should always be able to slow the idle to a stall with the idle screw. If
you can't something else is holding the butterfly open. A vacuum leak is
often mentioned, but whilst that will cause a high idle *for a given throttle
opening* you should still be able to adjust it out with the idle screw, as the
engine can't run on air alone. If it is running then some fuel must be
getting past the butterfly. In extreme cases wear in the butterfly spindle
and bushes can allow mixture to get past an otherwise fully closed butterfly,
but that is easily detectable by waggling the shaft up and down.
Make sure you have some free play in the throttle cable with the pedal
released, you don't want the butterfly hanging on the cable. As well as an
adjustment either on the inner or the outer at the carb end there is also an
adjustable stop at the pedal. With a combination of these two you adjust
things so that the pedal *just* hits the floor or stop as the carb is fully
opened, but leaves a smidgen of slack in the cable when it is released.
If not those try pressing the spindle down by hand. If that stalls it then
the shaft or butterfly is sticking. You can also get the butterfly
mis-aligned on the shaft so it isn't fully closing off the throat, about the
only way to check this is to remove the carb and squint through it against a
light. If the butterfly is the wrong way round this can happen, it usually
has chamfered edges where it closes to the throat. It can also have a notch
in one edge which must be the right way up.
PaulH.
----- Original Message -----
So the '76 B that is now moving again, has a very high idle, like 2000
rpm.
.
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