SU carburettor functional explanation101:
The basic secret of carb function is that inside each carb are thousands of
tiny gnomes; each with a small bucket. As you open the throttle, more of
these gnomes are allowed out of their house and into the float bowl, where
they
fill the buckets and climb up the carb's passages to the intake, where they
empty their buckets into the air stream.
But, if you don't drive the car for a while, bad things can happen. Tiny
bats take up residence in the chambers of the carb, and before long the
passages
are plugged up with guano. This creates a gnome traffic jam, and so not
enough bucketfuls of fuel can get to the engine. If it gets bad enough, the
gnomes simply give up and go take a nap. The engine won't run at all at this
point. Sometimes you'll have a single dedicated gnome still on the job, which
is
why the
car will occasionally fire as the gnome tosses his lone bucket load down the
intake.
There has been some research into using tiny dwarves in modern carburettors.
The advantage is that unlike gnomes, dwarves are miners and can often
re-open a clogged passage. Unfortunately, dwarves have a natural fear of
earthquakes, as any miner should. In recent tests, the engine vibrations
caused the
dwarves to evacuate the MGB vehicle and make a beeline for the nearest BMW
dealership. Sadly, BMW's are fuel injected and so the poor dwarves
met an unfortunate end in the rollers of a Bosch fuel pump.
Other carb problems can also occur. If the level of fuel in the float bowl
rises too high, it will wipe out the Section 8 gnome housing in the lower
parts of the carb. The more affluent gnomes build their homes in the diaphragm
chamber, and so are unaffected. This is why the car is said to be "running
rich".
If the fuel bowl level drops, then the gnomes have to walk farther to get a
bucketful of fuel. This means less fuel gets to the engine because the gnomes
get quite a workout from this additional distance, this condition is known
as "running lean".
The use of the device known only as the 'choke' has finally been banned by
PETG (People for the Ethical Treatment of Gnomes) and replaced by a new carb
circuit that simply allows more gnomes to carry fuel at once when the engine
needs to start or warm up. In the interests of decorum, I prefer not to
explain how the 'choke' operated. You would rather not know anyway.
Check out the new British Cars Forum:
http://www.team.net/the-local/tiki-view_forum.php?forumId=8
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