Solex 30 PICT/2 Carburetor Adjustment
This procedure also applies to the 30PICT/1 and 28
series carburettors having a single adjusting screw
on the side of the carburettor.
Before you begin to adjust the carburetor, the valves, points,
and timing should be set. This is important, and they should be
set in the order given below -- start with the engine cold, and
finish with it warm. These topics are addressed in the following
See our procedure for adjusting the
engine must be completely cold to set the valves.
inches is the factory setting for pre-1971 engines. Some folks
find that results in the valves being too tight when the engine
warms up, and use 0.006 inches.
1971 and up engines use 0.006 inches. The aim of the tappet setting
is to provide virtually no gap when the engine is at operating
See our procedure for setting
set the points at 0.016 inches. If they are pitted or damaged,
or if the rubbing block is badly worn, replace them. Put a small
dab of grease on the cam lobes whilst you are at it. Also pull
off the rotor arm and have a look at the spindle it sits on. If
there is a felt pad in there (some have it, some don't), put a
few drops of oil (engine oil is fine) on the pad to help lubricate
the distributor. Don't overdo it - just a few drops.
See our procedure for setting
usual timing is as follows:
with single vacuum distributor - 10BTDC (Before Top Dead Center).
This is set with the engine off (static timing).
with single vacuum distributor - 7.5BTDC. This is set with the
engine off (static timing).
with double vacuum distributor - 5ATDC (After Top Dead Center).
This is set with the engine idling, so that the retard vacuum
line is operating. It would be unlikely to see a double vacuum
distributor on a vehicle equiped with a 30PICT/2 or earlier carburettor,
as these have only one vacuum point on them, so this last paragragh
is included just to point out the difference in the double vacuum
set-up. It is conceivable to use a double vacuum distributor with
the retard vacuum line disabled, (then using the 7.5BTDC setting),
but the advance curve of this distributor may not suit the earlier
Any VW aircooled engine using the Bosch 009 or other centrifugal
advance distributor - 28-30 BTDC at 3000+rpm. It is important
to set the 009 at the maximum advance point - the total advance
varies on them, and the maximum advance is more important than
the idle, which usually ends up somewhere in the 5-8 BTDC range.
If you have non-oxygenated fuels of high enough octane (exact
octane requirements depend largely on compression ratio), you
can use 30-32 with the 009.
is very common to see the 009 distributor being used as a replacement
for the original vacuum distributors (which can be hard to find),
but you should note that the 009 was never developed for the beetle,
and was never used on beetles by VW. They do work, but not as
well as the appropriate vacuum distributor - often leading to
flat spots on acceleration, and a lack of 'pick-up'. Because they
have a lower maximum advance amount compared to vacuum distributors
(which can provide up to 40-42 degrees advance under the right
conditions), 009s will result in slightly increased fuel consumption.
See our procedure for adjusting the automatic
warm the engine up, take the aircleaner off the top of the carby
(if it's the oil filled kind be careful, you don't need a shoe
full of oil) and check that the choke butterfly is standing vertical.
If it isn't, run the engine some more to make sure it's throughly
warm, and check the choke butterfly again. If it is not standing
vertical, the butterfly needs adjusting or fixing (another topic).
It's important to set the valves, points timing and check the
choke before setting the carburettor, they all work together for
a smooth running engine.
Adjusting the Carburettor
The Brosol 30/31 Carburetor
There is a lever on the left side (left is left
side of car) with a cable connected to it. This is the Throttle
On the throttle lever is a small screw which sticks
out towards the back of the car. This is the Idle Adjustment
The idle adjustment screw rests on a strange-looking
flat piece of metal with steps cut in it. This is the Fast
Idle Cam, and works with the choke to give a reliable idle
on a cold engine.
The engine must be warm to set the carby, so that
the choke is off, and the Idle Adjustment Screw is sitting
at the bottom of these steps (at the BOTTOM, not on any of the
steps themselves). Directly beneath the fast idle cam on the left
side of the carburetor you will see a screw with a spring wrapped
around it. This is the Volume Control Screw.
On the side of the carburetor body is a barrel-shaped
object, about the size of a pen-light battery, with a wire connected
to the outer end. This is the Idle Fuel Cutoff Valve (solenoid).
This shuts of the fuel when you turn off the engine, to prevent
'running on'. Be sure the wire is connected and runs to the (+)
terminal on the coil. (This usually runs off the same wire which
attaches to the choke.)
Also make sure that this solenoid is screwed into
the carby snuggly, and not rattling loose. Don't overtighten it
though, it's got a fine brass thread and screws into aluminium
- both quite soft metals. You can test the operation of this solenoid
very easily. Turn on the ignition, and pull off the wire on the
valve. Touch the wire on the connector, and you should hear a
clicking sound as the valve inside moves. If not, check for 12
volts on the wire (small trouble light, voltmeter etc), and replace
the solenoid if required - if it's not working, you won't get
a proper idle, and you'll get rough running at traffic speeds
As stated previously, make sure your engine is
warm and the choke butterfly standing upright. Make sure the air
cleaner is ON when adjusting the carburettor--the engine expects
it to be there.
the Volume Control Screw in all the way - GENTLY PLEASE.
It is a needle valve, and you don't want to enlarge the hole
by forcing it home. Now unscrew it 2.5 turns. This is the starting
point for the adjustment.
Note: The Volume Control Screw controls the AIR volume, not the fuel volume. Screwing it in reduces the air and makes the fuel/air mixture richer. And of course turning the Volume Control Screw out increases the concentration of air and makes the mixture leaner.
the engine, and turn the Idle Adjustment Screw in or
out to set the idle at 850 RPM. I'll let you work out how to
measure 850 rpm - but it's a fast idle. (See our idle
turn the Volume Control Screw in slowly until the engine
speed begins to drop, then turn it out until the engine runs
at its highest idle speed. It should still be within about ½
turn from the start setting of 2.5 turns. If the hole has been
damaged by a previous careless person, you'll just have to do
the best you can. Now screw it in until the revs 'just' start
to drop - about 30rpm. This is the final setting.
the idle speed again with the Idle Adjustment Screw.
Don't slow the idle too much, 800-850 is about right. VWs need
a few revs at idle to keep the cooling air flowing, otherwise
when you coast to a stop at the lights after cruising at a good
speed, your hot engine won't get enough cooling air, and it
won't like you very much.
it - you're done. It should be purring like a kitten now.
* * * *