I am not the expert here but have rebuilt a few Z-S carbs. After a total
rebuild sans throttle shaft bushes I still could not get the idle to drop.
Same symptom as you describe. Snap the throttle and the idle would drop but
then creep back up. I pulled out the throttle shafts and polished them and
rebushed and the problem went away. Too much air. Now, if you want my theory
as
to why this "corrects" when you snap the throttle, I think it is because the
air fuel mixture balances temporarily, and the idle settles down. Soon the
motor discovers that the air fuel mixture is out of balance, and up she goes.
As I recall your original post, you have new shafts and bushes, bypass
valves, etc. I don't recall if you mentioned temperature compensators. If
those
aren't seating properly, this can contribute. See the VTR site for some
simple instructions on recalibrating the TCs.
I assume that you have:
Determined that your throttle plates are closed when the idle screw is
backed all the way off.
Determined that the cold start mechanism is functioning properly and is in
fact not engaged when the choke is all the way in.
Properly set needles and/or jets for initial start.
Properly set float level.
Determined that the bypass is assembled and set properly
Determined that temp compensators are seating properly
If this has all been done then I would do the following.
Warm the car up a bit and shut off. Disconnect your cold start cables and
make sure the mechanism is free to seat closed. Disconnect the brake booster
vacuum hose and plug at the manifold. Disconnect all other vacuum lines and
plug at the carb. Disconnect the carbs from one another at the shaft links.
Back off the idle screws all the way then advance until they just touch the
boss. Turn each idle screw in 1 - 1 1/2 turn equally. Start the car.
Report findings.
My car is a very early and I do not have the mandated plumbing, but
disconnecting and isolating should have no effect other than a few extra
hydrocarbons
for a few minutes.
David Lylis
69 TR6 CC26160L
60 TR3A TS74461LO
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