Hi Lani, If I was in your position my first job would be to remove the carbs
from the head ( I know its a chore ) and check if the throttle plates are
closing. The best way to do this is to look through the ports from the
manifold side. You should see no light showing or very little, and the
important point is that both throttle plates should be about the same. If
the plates are not seating perfectly then slacken the two screws that secure
the plate to the spindle so that the throttle plate is loose and apply
pressure to the throttle spindle and the plate should seat perfectly.
Tighten the two screws while keeping the pressure on the spindle. Make sure
that both throttle plates are showing similar levels of fit.
The uncentred jet must also be rectified and several checks should be made.
1 Check that there are no dents on the dash pot flange so that it seats
squarely on the carb body, any imperfections will cause the dash pot to
"kick over" when the screws are tightened.
2 Make sure the needle is not bent, and that it is inserted in the piston to
the correct depth.
3Check that the piston moves freely in the dash pot bore.
These are the main problem areas, and if these solutions do not work then
check the condition of the throttle spindles and bearings, the bottom jet
bearing , and associated parts.
My bet is on the throttle plate not seating correctly!!.
Keep us informed,
David Tinker
----- Original Message -----
From: "Lani Spahr" <lani_spahr@agilent.com>
To: <mg-tabc@egroups.com>; <mg-t@autox.team.net>
Sent: Monday, July 17, 2000 3:18 PM
Subject: SU balacing
> Hi all -
>
> Yesterday I embarqued on the final stage of my first thorough tune up of
my
> TD (I bought it last summer) which is carburetter (!) tune up and
balancing.
> I followed the procedure as outlined in Knudson's T Series Handbook. When
I
> came to centering the jet on the front carb I had a bit of trouble getting
> it centered. The problem was that it was centered with the locking nut
loose
> but when I tightened it down the piston did not seem to go all the way
down
> and "click" on the jet. After several tries I got it to center (I
think -see
> below). Now for balancing the 2 carbs:
>
> I adjusted the 2 throttle screws as described (until they just touch the
> plate and then one full turn CW), started the engine (which idled very
well
> at a slow speed) and listened with my tubing/stethoscope to the air
intakes
> at each carb. The front one (the one that I was having problems centering)
> was sucking MUCH more air than the rear, so to balance them I had to
adjust
> the rear one CW several full turns. Even backing off the front screw (to
the
> point where it isn't touching the plate at all) to get a balance results
in
> a very fast (2500 rpm) idle speed. If I proceeded to adjust the mixture
from
> this point I doubt that I could get the revs down to an acceptable speed.
>
> Now to the questions:
>
> 1. Do I still have an uncentered front jet, i.e. does an uncentered jet
> result in a greater air intake that I observe?
>
> 2. If not #1 above, do I have something wrong with the throttle plate? Is
it
> adjustable somehow other than with the external adjusting screws? As noted
> above, when both screws are adjusted the same the front carb is REALLY
> sucking air.
>
> 3. Anything else?
>
>
> Cheers,
> Lani Spahr - 1951 TD #5550
>
> Bruckner Symphony Versions Discography
> http://people.ne.mediaone.net/lspahr
>
>
>
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