As I recall, the mixture or 'volume' screw is located inside a narrow hole
in the carb body. You have to approach it from the windscreen position
pointing forwards. Get in there with a very slim headed conventional
screwdriver. The process involves turning down the throttle stop until the
care is almost stalling, and then fiddling with the said volume screw slowly
until you find the fastest tickover. Repeat the operation, possibly three
times, until you are sure the volume screw is right. Then finally adjust the
tickover to the required rate using just the throttle stop.
Yes you are correct in your memories.
The idle mixture and idle speed control work together. The speed control
adjusts the throttle plate / accelerator pedal linkage. The idle mixture
adjusts the fuel flow in the "progression" range of the carb. For those
interested in old technology in a carb the throttle plate resticts the air
flow. When fully closed the engine would stall were it not for the
progession holes. These are one or more bypass feeds around the throttle
plate closure position.
To adjust the idle mixture turn the screw in till the engine wants to stall.
Note the position. Unscrew the position till the engine hunts/lumpy. Note
Split the difference in half turns and set to midway. Now adjust the idle
speed control. Set to desire speed. Probably 850 rpm.
Now adjust the idle mixture again. Go to lean/cutoff and unwind (count the
half turns) till hunting/lump occurs. Backoff to the midway position.
Check the idle speed.
Repeat as necessary :-)
To adjust other than idle mixture one has to adjust the jet sizes and this
can become quite an involved and repetitive exercise.
And the jets are two brass tubes, plus two shorter screws, that drop
vertically down into the carb body. Four screws in line at the top are
visible. I recall getting some benefit to acceleration, or pedal response at
least, by changing the longer ones for tubes with slightly bigger jet size.
Yes, the emulsifier tubes, with a scattering of holes up the side of the
tube. Worth swapping and experimenting with, if you get the opportunity. I
had several carbs with various jets, to play around with.
So U finally rembered the "emulsion" tubes!
Main jet is at the bottom. The emulsion tube in the middle and the Air
Corrector/Correction at the top!
For twin choke carbs one of course has two of these assemblies.
I must admit this brings back memories of tuning my Uno (1.3) SX on the
road. Standing starts, fixed gear timer accleration etc. etc. I soon got
it down to a fine art and had 6500+ miles race track fun with her. Modesty
hat on but Nick and his Uno SX is(was) was very well known around many UK
circuits/clubs and astounded many cars and drivers as to what could be
achieved with 46BHP at the wheels AND a good handling car.
Today I have still have a Strada Abarth, Fiat Coupe, Stilo Abarth and
Barchetta but really miss my Uno. Underpowered she was but bags of fun on
the track and respected! :-)
Call me sad or what!
wrote in message
I really liked my two Unos. If you think you are sad - I am seriously
thinking of getting one for a couple of hundred, just to play around with
it. Also, great for carrying bits of furniture, etc., around with.
I remember the problem that ultimately led to my knowledge of the
carburettor. I kept finding little bits of black powder in the chambers, and
the car periodically stalled and died for ten minutes, after which it would
start up without a problem. That plagued me for maybe two years. Even after
I switched carbs, and engines, it still persisted.
Answers anyone? I found it, but this is a quiz for the bank holiday.
The strange thing was that the cylindrical mesh filter where the fuel goes
into the carb was not blocking up or collecting anything, even though the
bits in the carb seemed a lot bigger than the mesh. But yes, it was a poxy
little length of black rubber tubing connecting fuel pump to carb. I was
just cleaning the carb out in my kitchen for the umpteenth time, but this
time happened to have the tubing still with it. I casually tapped the tubing
on the counter and a little pile of powder appeared. Can you imagine the
relief, after two years, and even after episodes of being stuck on motorway
hard shoulders, pushing the car around, taking off the petrol tank to clean
it out, etc??
Yes, absolutely right. Even the 'experts' failed to pick it up at the time,
but maybe I am giving more clues here than I did then. But not to take away
your glory moment....
Where would you like to be prised??
This is good news and I hope stability remains.
This is all kind of funny / sad / strange etc.
In the old days decent mechanics new exactly how to setup carbs but were no
so good on modern fuel injection technology.
Today the reverse is true. Plug in the computer and wait for the readout!
We had a Fiat Tempra that was pinking. Dealer checked everything out, max
rpm/limiter, timing etc etc. No fault found.
I went back to 1st principles, got the old fashion timing gun out and found
that the TDC sensor was misaligned by 5+ degrees. ECUs take their
reference point from TDC/BDC and measure everything from there. Put the
sensor in the wrong position and everything esle will be incorrect!
I'm not sure which era I prefer. Older simpler and variable technology or
the modern so called precise and stable technology that ver goes wrong (in
yor dreams). Old technolgy most can be fixed, bodged, bypassed but modern
stuff often requires a cheque book to sort out :-)
Live and learn
at some level I love the old technology because of it's simplicity. However
I love the new stuff because of the increased performance. Back in the day
a engine came from the factory with very wide tolerences and a good mechanic
could increase the performance and relability by blue printing the engine.
Which was little more than rebuilding acording to the spec. Today they come
from the factory much, much closer to the spec. As far as the mess of
computer controls, well the problem there is not the computer but the
training of the folks who do the maintenance. Even with the computer,
internal combustion basics are still the same. And if you got a program
plan that explains what should happen when a mechanic with a tach, a vacumm
gauge, a VOM meter and a timing light can do everything that the computer
will do and as you demonstrated sometrimes more accurately.
Computers are a function of action reaction....at a given set of conditions
this will happen. There is just more of it. I would love to have fuel
injection and turbo performance on my little Spider..........maybe this is a
project in the making.
Find a rotten Lancia Beta Volumex for an engine transplant.
Or, if you're feeling really evil, don't forget that the Delta Integrale
is a Lampredi lump, so there's an easy 200-odd bhp available from one of
Steve H 'You're not a real petrolhead unless you've owned an Alfa Romeo'
http://www.italiancar.co.uk - Honda VFR800 - MZ ETZ300 - Alfa 75 TSpark
Strada Abarth 130TC lump will easily do the trick. Standard form 130BHP
with 130ft lb torque. The torque curve is the killer spec. FLAT (well
almost) across the entire rev range. 1st, 2nd, 5th and you are still
smiling. Do that in an Integrale (or other turbo car) and one might as well
stop and get the lunch box out.
Lets face it. *ANY* Fiat/Lancia twin cam Lampredi lump (with or without
turbo or supercharger) is going to be the bees knees!
Nick ///// ( am I biased or bothered?......)
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