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Re: [T3] Fake dual carb adjustment?


You can rig up a manometer to compare the vacuum with a length of clear
plastic tube - maybe about 1.5 metres (4 or 5 feet) would be enough.  Put
some kerosene (no worries if it gets into the engine) in the pipe, and let
it settle in the centre sag of the pipe to give maybe 6" each side of the
mid-point (amount isn't very critical, but put an elastic band around the
U-tube part to keep the arms close together).  Remove the air cleaner and
tape the ends to the air-cleaner support screws, symmetrically in each carb,
pointing down.  The movement of the kerosene surface in each arm shows the
amount of imbalance in the carb vacuums.  It's very easy to see if they are
balanced at speed too, but as you say, it isn't very critical due to the
balance-pipe(s).  Well-balanced carbs are really nice to drive with though.

I disagree that the mixture screws are used to adjust the idle speed.  The
VW method is to turn them in until the engine begins running unevenly, then
undo about 1/4 to 1/2 turn until it is smooth again.  Later info mentions
using a CO meter to check this.  The idle (throttle-stop) screws are used to
set the rpm and the balance (then the right-hand adjustable connecting rod
is matched to the distance between the spigots so it does not disturb the
setting).

If you have a spare air-cleaner assembly, you can solder a small spigot in
the air-cleaner over each carb and attach the manometer device, then adjust
with the engine under normal operating conditions for an even more
reassuring result.  I inherited such a device from a PO - much better than
inheriting problems!

Dave.
UK VW Type 3 & 4 Club
http://www.hallvw.clara.co.uk/
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