Fred Ki (ki@gf3.zycad.com) writes:
>> I have a '70 TR6 w/ ~140K miles, orig. engine, transmission & Z-S carbs.
>> After doing an engine tune-up (Platinum plugs, points & condenser, timing
>> & idle), I tried fooling around w/ the mixture (air/fuel) using the
>> special allen-wrench-in-a-barrel tool. Bad move. I think I probably
>> unscrewed the metering needle or something so that she runs with no high-
>> end power at all -- embarrassed to be overtaken by lunch trucks & beat up
>> Vegas on the highway doing 50 with the throttle petal floored. The mpg
>> drops to 1/2 of what I used to get (~20/2 = 10!).
Did you check the oil in your dashpots after adjusting the metering needles
(and after driving it for a few days). The dashpot in the Z-S (singular) on
my 1980
MGB would not hold oil for more than a day or two when I first got it. The
result
was very poor acceleration and a bit of "spitting back" under a wide open
throttle.
The problem was the "O" ring which seals the opening for the needle valve
adjusting screw in the bottom of the dashpot. If this is worn or dried out,
your dash pot oil
will leak out as fast as you put it in.
To replace the "O" ring:
1. Remove the piston from the carb.
2. Loosen the adjusting screw until the metering needle comes out.
3. Using a thin tool with a small hook on the end (l used a dentist's pick),
remove the star shaped clip which holds the adjusting screw in its place at
the
bottom of the dashpot piston. If you can get it to turn sideways, it will
come right out.
4. Remove the old "O" ring from the adjusting screw and replace it with a
new one. (Both the screw and "O" ring were available from VB for my MG).
5. Use your mixture adjusting tool to put the adjusting screw back in and
screw it back into the metering needle.
6. Drop the retaining clip down the bore on top of the adjusting screw and
use the same tool which you used to remove it to poke it around until it lies
flat.
make it lie flat. Then you can use a dowel and a small hammer to drive it
into place.
BTW, if your carbs _are_ holding oil, or if going back to NGKs fixed your
problem, ignore this advice. I have posted this to the whole net just in
case there
is someone else out there who might save the price of a rebuild for about
$4.00 in
parts and a half hour of labor.
Just as an afterthought, I have been using Champion N9s in my MGB with no
real problems. Does anyone on the net have any experience with a comparable
NGK?
Peter Schauss email: pschauss@aol.com
1980 MGB
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