Article - Solex carburettor data and information
PAForbes
systems, particularly those of a generation ago, but there is also a lot of
data on the 26, 30, 35, and 40 series of carburettors which may be useful for
those who have a carb and want to match it to a particular engine, or
vice-versa.
Of necessity I have had to ignore really old carburettors, as I have no
personal experience of them (up to the 1930's) Perhaps one of the newsgroup
could put a few words together on the older models as an add-on article ?
Most industrial engines had either an in-house carburettor or the makers went
to an established carburettor company such as Zenith/Solex. Most newcomers
finish up with a Lister 'D' or equivalent Petter, and both carburettors are
simple to strip and reassemble.
With an engine that is bought in running order, there is not a lot to do unless
the engine is obviously in distress. Cleaning of the in-line filter in the
banjo and any sediment in the carb fuel bowl is about as much as you need to
do.
If the 'new' engine is in a state of advanced wreckage, then your task is a lot
more involved.
Starting with dismantling:
Soak the whole carburettor and manifold (if attached) in diesel or WD40 to
assist with easing rusted threads and joints. Wait until the liquid has had a
chance to penetrate before trying to undo anything, and try to ensure that
tools are in good condition before you use them, particularly screwdrivers.
Remove the fuel inlet pipe and banjo, usually brass, and put in a box on one
side. If there is a small tubular gauze filter around the banjo bolt, keep it
safe in a matchbox where it will not get crushed. Discard the two banjo
washers.
Next see if you can remove any attached throttle linkages from the butterfly
arm, and then have a go at removing the nuts from the manifold (if still
attached) and remove the whole carb.
At this point, you should have the complete carb in your hands, and it is a
good time to take notes on numbers and fittings.
Lister 'D' carbs only had casting numbers, but Solex had a good reference
numbering system on their products, and they were probably the most successful
of the independent makers, along with Zenith in the USA.
The Solex system of numbering/labelling is fairly simple as follows:
The 'F' series came in two models:
The basic choice is of vertical uptake inlet - FV or horizontal sidedraught
inlet - FH.
Next there is the option of the float chamber position on the horizontal model,
adding D or G for right & left (in French - Droite and Gauche) Thus FHD
was a horizontal carb with right hand mounted float chamber.
In front of these letters is the number indicating the body inlet size, most
commonly 26 for 26mm, but 30, 35 and 40mm were also made.
Thus a 26FHG becomes 26mm size, horizontal inlet with left hand float chamber.
Note that the choke tube or venturi tube is calibrated according to engine
rating, and has a range of diameters, described as 'average diameters' in the
handbook.
Stud fixing centres for the various models are:
26mm - 48mm 30mm - 53mm 35mm - 65mm 40mm - 72mm
Mounting flange clearance holes sizes are 8.5mm for the 26mm and 30mm models,
10.5mm on the other two.
In case you are wondering, Solex was a French company, with registered offices
at
190, Avenue de Neuilly, Neuilly sur Seine, France.
Jet mounting devices are different on the two models, and there are a series of
graduated main jets, all with numbers stamped on them indicating the size in
hundredths of a millimetre, followed by another two-digit number which gives
the size and disposition of the drilled cross-holes. These drilled cross-holes
give various correction values of mixture at different air-flow rates over the
jet., and the numbers are 51,52, 54. The lower value giving less fuel
correction at low speeds than the higher numbers. (The number 56 is also used,
as an intermediate value between 51 and 52)
The G51 jet is the recommended 'starter' size as it's characteristics suited
most engines without adjustment.
The range of information published by Solex for matching carburettors against
engines was quite comprehensive, and the following formula was used:
A X A X C X N / 100000
This is the bore size squared, times the stroke, times the rpm at which the
engine develops its maximum power, divided by 100000.
This was then used on a table which I cannot print here, to determine which of
the various sizes etc to select. Briefly, a result below 11000 (10000 for FV)
was a 26 size, below 16500 (15300 for FV) was a 30 size, below 23000 (23500
for FV) was a 35 size and below 33000 (same for FV) was a 40 size.
Available average choke tube (Venturi) sizes were 12 - 18 for the 26 size, 19 -
22 for the 30 size, 23 - 26 for the 35 size, 27 - 32 for the 40 size.
Slow running jet ranges were 26FV or FH 050 - 055, 30-35 FV or FH 055 -
060, 40FV or FH 060 - 065.
Interestingly, the figures for FH and FV were different at the lower end,
evening out at the larger sizes.
If anyone is interested in the full set of figures, let me know and I will
photocopy the instruction book and send a copy for the price of the copying and
a stamp.
Stripping a Solex carb is pretty easy, as long as you take your time, don't
force anything that is tight and keep all the bits together. Many a project has
foundered because a vital bit from the carb has been mislaid, or damaged by
hamfistedness.
Generally speaking, horizontal inlet types had a flap behind a cover, with no
air filter, for the choke, while the vertical inlet type had a butterfly with
operating lever. 26FV type had the choke integral with the inlet pipe and
float casting, while the 30, 35 and 40 sizes had a bolt-on casting with the
choke flap in.
A number of pre-machined pipes and bends and T's were available from the
factory, to facilitate fitting of the carb to an engine, and Solex obviously
supplied kits of bits to OEM's where necessary.
Because of the huge range of applications for the 26 series in particular,
there is a very distinct possibility that slight variations of settings exist
between carb's of the same basic style and size. Thus although for example
Bamfords used the 26FHG in a number of applications, there are also other
engines which would have had the same basic carb with different venturi size
etc. The possible combinations run into thousands, so check the stamped figures
on the float chamber by the 26F... number, and check with another known good
engine to see if yours is right.
There is also a series of parts lists and exploded drawings in SE, (from
Richard Cornell I believe) which also gives some application information.
That's about all for now,
Regards to everyone, Peter
Peter Forbes Home Fax: +44 (0)1933 355557 Work Fax +44 (0)1582 416000
richard
ocassions, I have not tried it myself and it is not April 1'st
--
Regards - Richard
Near Norwich - UK
website - http://www.oldenginehouse.demon.co.uk
updated June '98 (signal box page)
PAForbes
the following:
Wintergreen - a plant of genus Pyrola, also of Chimaphila: a plant of genus
Gaultheria, whose oil is an aromatic stimulant, used in flavouring
confectionary and in medicine.
So if anyone has any of this, can we have some extract please to try Richard's
suggestion ?
Regards, Peter
Martin E Phillips
<pafo...@aol.com> writes
>Ref Richard's suggestion, I looked up wintergreen in the dictionary and found
>the following:
>
>Wintergreen - a plant of genus Pyrola, also of Chimaphila: a plant of genus
>Gaultheria, whose oil is an aromatic stimulant, used in flavouring
>confectionary and in medicine.
>
>So if anyone has any of this, can we have some extract please to try Richard's
>suggestion ?
You can buy it at any chemist. It might be a bit expensive if you have
any large components to soak, but it will make them smell beautiful.
Wassail!
Martin, coming out of lurking.
--
Martin Phillips: Web page http://www.g4cio.demon.co.uk/index.html
Home brewing, black pudding, boats, Morris Dancing and more