<VV> RE: YH Pump

[grant young]

<<In rebuilding my YH Carb, I noticed that the accelerator pump only
"pumps" when the throttle first comes off of idle. Thereafter, the
accelerator pump appears to be at its maximum extension. If you continue to
open the throttle, the pump link affects nothing for about an 1/8" and then
finally moves the metering rod arm only for the final 1/8">>

The pump is "pulled" down into it's cavity during operation by engine
vacuum or a pressure differential, as you prefer, so it does "pump" (push)
at other times than when starting and coming off idle. You appear to have
it adjusted and installed correctly. You will also notice that the pump
shaft connector link is bent to act like a cam of sorts when it activates
the pump. The upper springs that keep the metering rod arm in place were
changed in the Corvair application from a single heavy duty spring used in
the Corvette and Nash applications for whatever reason. It is not a great
design, having been developed in the early 50's, so there are a few flaws
you have to live with. You might want to check to be sure there is no wear
in the hole in the pump lifter link where the connector link fits, as this
will delay pump action. You can also switch to a later model carb to gain
1/8" in venturi diameter. Hope this helps,
Happy New Year,
The Carbmeister