Solex Carburettor Handbook Solex Carburettor Types FV and FH
FV & FH Type SOLEX Carburettors - FITTING & INSTRUCTION BOOKLET No 3 TABLE OF CONTENTS Page numbers are from the original booklet and are retained for reference within the text of the sections FITTING
Detail of Jet Assembly
Page 16
Choice of Carburettor & Pictures
Page 3
Adjustment for Power
Pages 17-18
Directions for Fitting
Page 7
Determination of the Size of the Carburettor
Page 19
Induction Pipe
Page 7
Table of Adjustments
Pages 20-22
Parts for Assembly of Same
Page 7
Throttle Control
Page 8
Flooding
Pages 23-25
Petrol Union & Filter
Page 9-11
Difficulty in Starting
Pages 25-28
Easy Starting Device
Page 9-11
Bad Slow Running
Page 28
Control of Easy Starting Device
Page 9-11
Bad Acceleration
Page 28
Operating the Strangler
Page 9-11
Insufficient Speed
Page 29
Flange with Governor Throttle
Page 11
Overheating
Page 30
Knocking
Page 30
ADJUSTMENT OF CARBURETTOR
DIAGNOSIS OF FAULTS
Dismounting
Page 12-13
Excessive Consumption
Pages 30-31
Determination of Adjustment
Page 12-13
Troubles Due to Suction Operated Tanks
Page 32
Slow Running Adjustment
Page 13-15
Troubles Due to Air Filters
Page 32
Solex Carburettor Handbook Solex Carburettor Types FV and FH DIRECTIONS FOR FITTING THE F TYPE SOLEX (Page 3) FITTING. The F type Solex carburettor is available in 2 types:-
The Type FH with a HORIZONTAL offtake (picture 1)
The Type FV with a VERTICAL offtake (picture 2)
The Type FH includes model FHD (float chamber on the right-hand side) and model FHG (float chamber on the left hand side) the emplacement of the float chamber being determined by the direction in which it is required to place the air intake.
CHOICE OF CARBURETTOR. The choice of the carburettor consists in the determination of:(1) The most suitable type to fit to the motor (FV or FH) (2) The size of the carburettor and its adjustment. 1. CHOICE OF THE MODEL. The choice of the model is generally determined by the disposition of the induction port and the shape of the pipe. The SOLEX type FV (with vertical offtake) can always be adapted whatever may be the disposition of the port. The SOLEX type FH (with horizontal offtake) is only intended for monobloc engines having a single induction port and when fitting same it is necessary to be sure that there is sufficient head of petrol to supply the carburettor regardless of the inclination of the car or appliance. It is recommended, when the carburettor is the FH type to select FHD or FHG so that the float chamber will be at the front end of the engine when the carburettor is mounted. 2. CHOICE OF DIAMETER. In speaking of the diameter of the carburettor, we intend to convey the diameter of the offtake at the flange and the various types described below are described according to the above measurements in millimetres. The carburettor should be equal or slightly larger in diameter than the induction port to which it bolts. The choice of the carburettor having a direct bearing upon the adjustment, is dealt with at greater length in a special reference to this matter in part two of this booklet.
DIRECTIONS FOR FITTING & ADJUSTING THE F TYPE SOLEX (Page 4-5) Sectioned View of Type FH with a HORIZONTAL offtake (picture 4)
PARTS LISTING FOR FH CARBURETTOR A* - Main Jet cap C - Throttle Spindle D - Spindle End Nut E - Dismounting Nut
G* - Main Jet
H - Throttle Chamber
h - Carburettor Body
j - Main Jet Carrier Washer
K* - Choke Tube
L - Throttle Lever
I - Strangler Lever
N - Air Bell
O* - Float Chamber
P - Swivelling Filter Union
R - Strangler Pull-Off Spring
r - Locking Spring For The Slow Running Adjustment S - Abutment Plate Jet r1 - Locking Spring For The Auxiliary Mixture Adjusting Screw t - Main Jet Carrier
U - Choke Tube Fixing Screw
W - Screw for Adjustment of Auxiliary Mixture
T - Air Bell Fixing Screw V - Butterfly Z - Slow Running Screw
* Parts marked with an asterisk will be marked with one or more numerals. It is necessary with all orders to quote the number of the carb part required and at the same time the size and number of the carburettor which will be found stamped on the outside of the float chamber under the petrol union. The size of the jets and choke tube and the year and horse power of the engine should also be mentioned.
Sectioned View of Type FV with a VERTICAL offtake (picture 5)
PARTS LISTING FOR FV CARBURETTOR b - Strangler Shutter A* - Main Jet Cap C - Throttle Spindle Stop c1 - Strangler Shutter Spindle
e - Body Assembling Screw
F - FLoat
G* - Main Jet
g* Auxiliary Jet
H - Throttle Chamber
h - Carburettor Body
j1 - Man Jet Carrier Washer
J2 - Needle Valve/Filter Union Washers
J3 - Large Filter Union Washer
K* - Choke Tube
L - Throttle Lever
I - Strangler Lever
O* - Float Chamber
P - Swivelling Filter Union
p - Float Needle
Q - Filter Union Nut
t* - Main Jet Carrier
U - Choke Tube Fixing Screw
V - Butterfly
v1 - Strangler Shutter
X - Needle Valve Seating
* Parts marked with an asterisk will be marked with one or more numerals. It is necessary with all orders to quote the number of the carb part required and at the same time the size and number of the carburettor which will be found stamped on the outside of the float chamber under the petrol union. The size of the jets and choke tube and the year and horse power of the engine should also be mentioned.
POSITION OF THE CARBURETTOR The first question to decide is the best position in which to mount the carburettor. This is generally determined by the existing pipe work layout which one can usually employ by the aid of a counterflange which we supply as a supplementary fitting (see table A) The carburettor should be mounted in such a way that the pipe work is as simple as possible without any local enlargements in its diameter and without any hairpin bends. When the original pipe work is not provided with any form of heating by exhaust contact, it is usually possible in the case of vertical carburettors, to provide for heating by a hot air pipe and an exhaust muffle. Where the horizontal types are concerned, there is no necessity for any other heating than that obtained by conduction from the cylinder walls. One should always be careful to fit the carburettor where possible in such a position that the float can easily be withdrawn, for otherwise the advantages of accessibility offered by the SOLEX design are lost. Excepting in the case of pressure fed fuel, when the position does not matter, the carburettor should always be sufficiently low to allow 10% drop from the bottom of the fuel tank to the petrol union above the float chamber. Generally speaking there should be sufficient room at the side of the carburettor to permit the hand to be placed underneath in order to remove the float chamber, and it is well to arrange the petrol pipe in such a way that this space is not obstructed thereby. In the majority of cases it is advisable to mount the carburettor with the float chamber in front.
DIRECTIONS FOR FITTING THE F TYPE SOLEX (Page 7) INDUCTION PIPE The induction pipe should be of uniform diameter equal or slightly less than that of the carburettor offtake. The pipe must be as simple as possible and free from any sectional variations. Local enlargements tend to cause deposition of the fuel which is most undesirable and for the same reason it is well to avoid any local depressions below the mean lower surface level of the pipe work where any fuel is likely to collect. It is most important also that the flange shall be quite free from air leakage for a lack of tightness at these joints has a very considerable effect upon starting and even slow running. In the case of 6 cylinder induction pipes difficult and more involved factors arise, and it is preferable to consult us before assembling such.
CARB FLANGES
In order to facilitate the assembly of induction pipes we make and stock special pipes and adaptors for fitting the Solex to a number of cars on which they are already not fitted as standard.
MACHINED PIPE LENGTHS, T PIPES & BENDS
A list of these will be sent on request. We supply for other and unclassified motors a variety of pipe lengths, tee pieces and bends from which it is generally possible to assemble an induction pipe to the fitting requirements of the cylinder block. See above table of these parts for each particular size of carburettor.
DIRECTIONS FOR FITTING & ADJUSTING THE F TYPE SOLEX (Page 8) THROTTLE CONTROL The throttle control of the Solex is provided for by means of an abutment or throttle plate (see picture) which is fixed on the end of the spindle and is provided with a fixed limit opening screw which is non adjustable and with a spring loaded adjustment slow running screw. On the outer part of this plate there is fixed a small dowel pin which engages with a convenient hole in the throttle lever, thus permitting same to take up any position required by the control at intervals of 45 °.
The throttle lever is usually mounted on the left hand side of the carburettor looking in at the air intake in the case of the vertical models, and at the upper part in the case of the horizontal models. In certain cases it is necessary to have a different control (as regards the direction of opening above or below and the position of the lever, right or left) The F type carburettors show in the above respect the advantage over previous models in that it is possible to mount the throttle chamber in four different positions, this facilitating the adaption of the existing control.
In order to modify the direction of the throttle spindle, it is only necessary to dismount the throttle chamber (see previous pictures) by removing the four screws by which it is attached to the body of the carburettor. After placing the throttle chamber H in the required position, it should then be carefully be remounted and the screws thoroughly retightened to avoid any air leakage. To alter the position of the throttle lever, it will be necessary to dismount the abutment plate (see picture at top of this page) and interchange the respective positions of the slow running adjustment screw and limit screw which are mounted on this plate, which, together with the lever can then be fitted on the opposite side of the spindle, the packing washer thereon being reversed to the opposite side to fill up the clearance. To facilitate the adaption of the control we can supply, if required, a ball joint (see picture immediately above) which gives unrestricted movement and perfect freedom. When fitting the control system it is advisable if possible to restrict to the utmost the number of joints between the accelerator pedal and the throttle lever in order to avoid the play which will otherwise result from a multiplication of articulations. In cases where the latter is necessary it is advisable to attach a light spring to the throttle lever itself to keep a constant thrust on one face of all the joints and avoid the uncertainty of low speed control which would otherwise result from slackness.
DIRECTIONS FOR FITTING & ADJUSTING THE F TYPE SOLEX (Page 9-11) PETROL UNION & FILTER The F type carburettors are delivered with a filter which is situated in the swivelling union (see picture below) It will be observed that this filter is not of the decanter type for the float chamber of the carburettor is so designed that the main jet take-off, instead of being at the bottom, is some little distance above same, so that any water or fine sludge that passes the filter can accumulate up to a fair quantity without getting through into the jet passages, and can be easily removed by dismounting the float chamber, which is quickly accomplished.
In order to obtain a correct flow of petrol it is always advisable to give the fuel pipe a mean downward inclination of 10% between the petrol tank and the top of the carburettor.
EASY STARTING DEVICE Certain engines when cold present considerable difficulty in starting, especially with heavy petrol or with Benzole. During the winter months especially a considerable effort is sometimes necessary and a temporary enrichment of mixture is required. In addition to this, the common use of electric self-starters necessitates some provision being made for ease of starting in order to save the batteries, and to cater for this necessity and assure immediate starting in all circumstances we have arranged for a special strangling device to operate on the air entrance, actuated by means of a lever which will close off the air at will. In the FV carburettors, the strangler (see picture below) takes the form of a shutter pivoted on its own spindle and placed in the air intake of the carburettor. In the 26FV type of SOLEX the strangler is integral with the float chamber (see sectioned drawings at the start of the book on page 6) In the 30, 35 and 40 FV it is in a separate chamber as shown below. This is maintained in the fully open position during ordinary running by means of a spring, and for starting purposes it is temporarily closed by operation from the dashboard. The facilitate the installation of this control the strangler lever is drilled at both ends (see picture below) In the case of the FH type carburettor it takes the form of a modified bell in which a special shutter is mounted.
INSTRUCTIONS FOR OPERATING THE STRANGLER If the temperature is fairly high (10° to 15°) it is usually possible to start without taking any special measures, simply by depressing the self-starter button, but if the temperature is low it is usually necessary to operate the strangler and this is generally carried out by means of a knob or lever placed on the instrument board (see picture below)
THE MOST EFFICACEOUS METHOD OF HANDLING THE CONTROLS IS AS FOLLOWS:Turn the engine a few times with the strangler completely shut and throttle partly open, but with the ignition switched off. This will serve to charge the cylinders with a rich mixture. Now switch on, release the strangler slightly and on operating the self-starter, the engine should fire immediately, after which it is generally advisable to release the strangler shutter gradually, and for the first few minutes during cold weather, run with it in a slightly closed position. When the above method is unsuccessful, please refer to the section on "Diagnosis & Faults" on page 23 which deals generally with troubles incidental to difficult starting. It is generally advisable, after starting from cold to have the strangler slightly closed for a short distance to give the motor time to warm up sufficiently to take the throtlle unassisted.
STRANGLER CONTROL KNOB & CABLE The facilitate this we provide a special dashboard knob complete with steel cable (see picture above) and anchorage which can be mounted on the instrument board and attached directly to the strangler lever. These parts can be supplied to order.
DIRECTIONS FOR FITTING & ADJUSTING THE F TYPE SOLEX (Page 11) Governor Throttle In order to provide for those cases in which the engine is governed, we can supply if required a special counterflange embodying a throttle which is operated directly by the engine governor.
DIRECTIONS FOR ADJUSTING THE F TYPE SOLEX (Pages 12-15) The elements concerned in the adjustment of the SOLEX are:The Choke Tube (K on the drawings on page 4 & 5) The Main Jet (G on the drawings on page 4 & 5) The Auxiliary Jet (g on the drawings on page 4 & 5) The F type SOLEX comprises in addition an auxiliary mixture regulating screw (W on the drawings below) which is intended for refinement of the idling adjustment.
DISMOUNTING In order to dismount the carburettor for adjustment or cleaning, it is only necessary to loosen the two screws (E in drawings on page 4 & 5) and remove the float chamber with the hand when immediate access will be obtained to both jets without the use of any special spanner and without breaking any joint. When remounting be sure that the float chamber is correctly in place and tighten the screws 'E' moderately.
To dismount the choke tube (K on the drawings on pages 4 & 5) remove the outer bell in the case of horizontal carburettors and loosen the choke tube fixing screw placed at the upper part of the body in the FH carburettors and at the side in the case of the FV carburettors, when the choke tube itself can be easily withdrawn. When remounting, note that the choke tube (K) numbers indicative of size and type are stamped on the atmospheric side in the case of the horizontal and at the bottom in the case of the vertical carburettors. To dismount the main jet (G) remove the jet cap (A) To dismount the auxiliary jet (g) unscrew it by the aid of a small spanner.
DETERMINATION OF ADJUSTMENT The adjustment of the SOLEX Carburettor consists in:1) The determination of a suitable auxiliary jet (g) to give the best slow running, and:2) The best size of main jet (G) to give the necessary speed, hill climbing, power and pick up. As regards the choke tube (K) the diameter of this part can generally be determined by the table of adjustments.
SLOW RUNNING ADJUSTMENT During slow running, the petrol is supplied by the special auxiliary jet (g on drawing below) The number stamped thereon is indicative of its size in hundredths of millimetres and the jet should in no circumstances be reamered for its output is originally determined by means of fluid flow.
The slow running adjustment is carried out entirely regardless of the main jet setting and resolves itself into two operations:1) MIXTURE ADJUSTMENT Try, to commence with, one of the jets indicated in the adjustment table on Page 20 selecting same as per the size of the engine. TOO RICH A MIXTURE Is recognised :a) By a rhythmic hunt or surge which the engine develops when warm. b) When the motor stops after having been idling some time in this way and the throttle is opened, a certain amount of petrol drops from the carburettor. c) The plug points will generally be found covered with a coating of soot. In such a case chose a jet one size SMALLER INSUFFICIENT PETROL: Is, on the contrary recognised by an irregular misfire when idling and by difficulty in starting. In such a case one uses a LARGER auxiliary jet. It is generally desirable to have the auxiliary as large as possible consistent with the avoidance of hunting when idling. 2) ADJUSTMENT OF THE IDLING SPEED. Having determined the adjustment from a mixture strength point of view, the next requirement is the adjustment of the idling speed. To do this the slow running screw on the abutment plate is reduced until the required minimum speed is obtained. The carburettors type F are provided in addition with an Air Regulating Screw (W on drawings above) for refinement of the auxiliary mixture. On rotating this screw outwards a slight air leakage is produced which reduces the strength of the mixture and vice-versa. By careful regulation therefore extreme correctness of mixture strength can be obtained easily. It is best to commence by having it screwed fully home which will give the greatest richness and then gradually unscrewing it until the best performance is obtained. At the same time the slow running screw on the abutment plate can be reduced and by means of a suitable cooperation between these two members a perfect tickover will be obtained, the air regulating screw W being automatically locked in position by the spring. It is well to make this adjustment when the engine is only moderately warm, for otherwise when cold the mixture will be found to be too weak and starting very difficult.
DIRECTIONS FOR ADJUSTING THE F TYPE SOLEX (Page 16) COMPOSITION OF THE JET ASSEMBLIES The assembly represented below is composed of three parts, viz: jet-carrier, jet cap and main jet, and is described as "Assembly 12"
ASSEMBLY 12 JET-CARRIER This is called jet carrier 12-300 and is marked with the numeral 12 (see left-hand picture, lower item)
JET-CAP The jet-cap 12X300 is employed in the vertical carburettors (see right-hand picture, lower section) The jet-cap 13X300 us used in the case of horizontal carburettors (see right-hand picture, upper section) In both cases the second number 300 indicates the diameter in hundredths of millimetres of the lateral holes 'A' drilled at the lower part of the cap (righthand picture)
MAIN JETS The main jets (left hand picture, top section) are made in four types. They are designed and marked with numbers indicating in hundredths of millimetres the diameter of the calibrated orifice, followed by the two-digit numbers 51, 52, 54 or 56 which characterize the diameter and disposition of the lateral holes A,B,C,D (left picture, upper section) These holes determine the correction of the jet, that is to say, the variations in output correspond with different suction values.
Thus the G X 51 has a lower correction, that is to say, it will give greater richness at high speed and relatively lower richness at low speeds than the jets 52 and 54 which are progressively higher in correction than 51, that is to say, that all these jets, assuming the same richness when all out, will give mixtures more and more rich at lower speeds as the numbers increase.
The jet G X 56 is not progressive numerically, but gives an intermediate figure of correction between G X 51 and G X 52. The correction to be adopted depends on the adjustment of the engine, the type of induction pipe and upon several constructional points in the motor itself. It is not therefore possible to determine the actual adjustment by calculation, but is easier to consult us if any difficulties are encountered, for tests have been carried out by us on practically all standard engines. If for some reason the adjustment will not conform to ordinary practice, we give on the following pages a series of hints by which it may be experimentally determined.
DIRECTIONS FOR ADJUSTING THE F TYPE SOLEX (Pages 17-19) ADJUSTMENT FOR POWER (Pages 17-18) It is necessary first to determine the size of the choke tube (K) and this can be obtained from the Adjustment Table and formulae on Pages 20 & 21, the diameter of the choke tube being stamped on the inside of the waist, the figures representing same being in millimetres. DISMOUNTING THE CHOKE TUBE. In order to dismount the choke tube it is only necessary to remove its retaining screw. In the case of horizontal carburettors, in addition to the above screw the choke is also maintained in position by the main jet cap which passes through it, and the float chamber must therefore be removed before the choke tube can be withdrawn. SELECTING MAIN JET SIZE. The size of the choke tube having been decided upon, the adjustment now becomes a question of determining the best size of main jet (G) to use. To determine this, consult the table on Page 20 which gives the average sizes of main jet required with definite choke tubes. In some cases it is necessary owing to individual peculiarities of the engine, to vary the main jet size up and down by one or two sizes. REMOVING MAIN JET. To remove the main jet (G) unscrew the cap (A) when the jet can be withdrawn by the fingers. This can be effected without losing any petrol and without having to break a petrol joint. When re-mounting, do not use undue force when screwing down the jet cap, and thus avoid injury to the jet. DO NOT IN ANY CIRCUMSTANCES use a reamer on the calibrated hole which is corrected by fluid flow and must not be interfered with. SIZE & TYPE OF JET TO START WITH. The type of jet with which it is best to commence is G X 51 because this will suit the greatest number of engines and it gives better economy than jets of higher correction. Generally speaking it is advisable to use as small a jet as possible consistent with obtaining the required power. This jet is generally one size larger than the number which gives obvious indications of poverty. One can recognise a poor mixture by the tendency to fire in the carburettor when accelerating. TWO DIFFERENT JETS GIVING THE SAME PERFORMANCE. When two jets give the same performance in point of power and pick-up it is of course advisable to choose the smaller in order to save petrol. The main jet (G) therefore should, if possible, be used in type 51 provided the capacity for maintaining power on hills and acceleration is satisfactory. In cases where any of these points leave a little to be desired it may be necessary to revert to higher corrected types such as G X 52 or G X 54 which will give a better performance on hills or during acceleration. When one is obliged to use a jet of higher correction, it is at the same time necessary to increase its number in order to maintain the same degree of richness when all out. For example; if after having found that it is necessary on a given engine fitted with a 110 X 51 jet to change, for certain reasons to a higher correction, one would then use 115 X 52, or, if a still higher correction is necessary, 120 X 54. It is always best, however, to use as low a correction as possible for purposes of economy.
DETERMINATION OF THE SIZE OF THE CARBURETTOR (Page 19) 1) Carburettor Horizontal or Vertical. As a rule the former type is always employed in the case of monobloc engines with a single port. It is necessary, however, to note that the position of the petrol tank is sufficiently high to give the required head of petrol even on the steepest hills. The vertical type is almost invariably employed in the case of external manifolds. 2) Choice of Size. Generally speaking one selects a carburettor the diameter of which corresponds with the internal measurement of the induction pipe or port, but it is also well to consult the tables on Page 20 & 21 which take into account the general characteristics and size of the engine Bore A, Stroke C and Rpm N.
DIRECTIONS FOR ADJUSTING THE F TYPE SOLEX (Page 20-22)
To make use of this table it is necessary to employ the formula:- A² C N / 100,000 Where: A is the bore of the engine in millimetres C is the stroke of the engine in millimetres N is the rpm at which the maximum power is obtained After having determined the value of A² C N / 100,000 and chosen the type of carburettor, FH or FV, one takes in the part corresponding to the type of carburettor, the number in the first column immediately below one of the definite numbers. One will notice that in the second
column the size of the choke tube will be found, and in the third column the jet size (G X 51) and in the fourth column the size of carburettor. These instructions apply especially to 4 cylinder 4 stroke engines, to 8 cylinder engines fitted with two carburettors or one double carburettor operated as two, BUT for 6 cylinders take a choke tube one size bigger and with it corresponding jets. For a single or two cylinder motor take, on the other hand, a choke tube one size smaller and with it corresponding jets. AUXILIARY JET SIZES The following table indicates auxiliary jet sizes to be fitted to the chosen carburettor:-
EXAMPLE 1 We will suppose that it is required to know the adjustment in the case of a 4 cylinder engine of 75mm bore and 120mm stroke giving its maximum power at 3000 rpm. The formula A² C N / 100,000 produces a value of 20,250 after substitution of the values of A,C & N. If the engine requires a horizontal carburettor (FH) one then looks in the left hand section of the larger table above to find the first figure immediately below 20,250. This is given in the table as 19,500. Following across the table from that figure we are given a Choke Tube size of 25mm, a main jet size of 130 X 51 and the fourth column shows that the carburettor size will be 35. The smaller table on this page gives an auxiliary jet size of 055 to 060 for this size of carburettor. One therefore orders the carburettor in the following manner:1 Carburettor 35 FH (see Page 3 to get the indication D or G (D for Droit or RIGHT, G for Gauche or LEFT) for the float chamber position, thus 35 FHG assembly 12, K=25, G=130 X 51, g = 055.
EXAMPLE 2 In the case of a 6 cylinder engine of 75mm bore and 120mm stroke giving its maximum power at 3000 rpm. The formula A² C N / 100,000 produces a value of 20,250 after substitution of the values of A,C & N, the same as the 4 cylinder engine in Example 1.
If the engine requires a vertical carburettor (FV) one then looks in the right hand section of the larger table above to find the first figure immediately below 20,250. This is given in the table as 19,500. Following across the table from that figure we are given a Choke Tube size of 26mm, a main jet size of 130 X 51 and the fourth column shows that the carburettor size will be 35. The smaller table on this page gives an auxiliary jet size of 055 to 060 for this size of carburettor. Because it is a six-cylinder engine, the main jet will be increased to 135 X 51 from the table recommendation of 130 X 51, while the carburettor size will remain at 35mm. One therefore orders the carburettor in the following manner:1 Carburettor 35FV (no requirement to select which hand the float chamber will be on) assembly 12, K=26, G=135 X 51, g=055.
DIAGNOSIS OF FAULTS IN THE F TYPE SOLEX (Page 23) There is never a question of definite failure of the SOLEX carburettor. It is simply a matter of locating errors in the selection of jets and choke tube. It is advisable always to carry out adjustments with a definite method and never to do more than one thing at a time for by such a way it is impossible to determine which detail of adjustment was at fault.
FLOODING INSUFFICIENTLY TIGHTENED JOINTS In the SOLEX carburettor there are four joints:The Jet Carrier Washer The Float Needle Valve Washer The Two washers of The Petrol Union The latter being exterior, they will readily disclose any leakage, but a leakage due to the needle valve being screwed insufficiently tightly into its seating in the upper part of the carburettor, will cause the level to be raised and resolve itself into a drip at the main jet. The first thing to do when any evidence of this is observed therefore, is to verify the tightness of all these four joints. GRIT ON THE FLOAT NEEDLE SEATING This trouble is very often in evidence in the case of carburettors not provided with a filter, especially shortly after being fitted, for in new petrol pipes which have been annealed and bent, flakes of copper oxide are often set free which can readily lodge in the seating of the needle and cause flooding. PUNCTURED FLOAT In this case the Petrol which leaks into the float increases its weight and a higher level results causing flooding at the main jet. In such a case the best cure is either to have a new float or if the leakage is a small one, it can be stopped with solder. Before doing so, however, the float should be put into boiling water which will serve the double purpose of locating the leakage by bubbles and boiling off its petrol contents. LEVEL TOO HIGH The simplicity of the constant level arrangements of the SOLEX render this case extremely rare. It can occur, however, where light spirit is used in a carburettor fitted with a float suitable for heavier fuel or if the needle valve has become worn. In this case either a new and lighter float must be obtained or a needle valve of normal length. The weights of floats for 730 spirit are as follows:26 grammes for 26 and 30mm carburettors 69 grammes for 35 and 40mm carburettors CHECKING THE LEVEL This is a very simple process in the SOLEX. One has merely to dismount the float chamber, unscrew the main jet cap, take out the main jet and mount the float chamber again in position with the main jet carrier sticking out of the side. Turn on the petrol, when the height to which it rises can be observed. In the case of ordinary spirit it should be approximately 3mm from the top. There is no functional disadvantage in having the level higher than this, but the above limit is mentioned in order to avoid flooding when the car is left standing on a steep incline.
EXCESS OF PETROL PRESSURE For exhaust operated auxiliary petrol tanks or for ordinary gravity feed, 26mm carburettors are supplied with a needle valve of which the seating is 2mm, while the 30,35 & 40mm carburettors are take a needle valve of which the seating is 2.5mm. When the head of petrol is abnormal (6 to 8 feet) or when the petrol tank is pressure fed, the buoyancy of the float may be insufficient to keep the needle on its seating against this weight of fuel. This is remedied on the 30, 35 and 40mm carburettors by replacing the standard 2.5mm seating with the smaller one having a seating of 2mm. The latter can be supplied to order.
DIAGNOSIS OF FAULTS IN THE F TYPE SOLEX (Pages 25-28) Page 1 of 3 While the carburettor plays a considerable part in the question of starting, there are also other factors which have a bearing thereon, especially when starting from cold and these should be examined on the following lines:-
DIFFICULT OR IMPOSSIBLE STARTING - CARBURETTOR FAULTS CARBURETTOR SETTINGS Starting becomes proportionately more difficult as the adjustment of the carburettor becomes leaner. To facilitate starting it is always advisable to have the slow running adjustment a trifle on the rich side, which can be carried out by means of the small spring loaded screw which regulates the auxiliary mixture. If the main jet is too small, it will similarly have an adverse effect upon starting from cold. It is generally advisable to employ one size bigger main jet during the winter months. FLOAT LEVEL TOO LOW If the specific gravity of the petrol is too high, the level can be so low that starting becomes difficult. In that case it is advisable to change the float for a heavier one or employ a lighter spirit. DEFECTIVE SLOW RUNNING Check first the adjustment as described on Pages 14 & 16, but if by this means it is not possible to locate the trouble, it is probably owing to air leakage at some point in the induction system, possibly via the inlet valve stems in their guides. In this case use an auxiliary jet one or two numbers larger than normal, being careful not to exceed the size required, for in such case hunting will occur. When equal results are obtained with the two jets it is generally desirable to use the larger. Before altering jets it is always wise to see that a partial obstruction is not the original cause. STRANGLER NOT CLOSING PROPERLY It is well to assure oneself that when in the starting position the strangler shutter closes completely. If it does not do so, check over the control generally and adjust same so that when operated from the dashboard the shutter entirely obturates the entrance to the choke tube. THROTTLE OPEN TOO WIDE OR NOT WIDE ENOUGH In order to get easy starting during very cold weather, or when the engine has not been used for some little time, the best plan is to open the throttle gradually and at the same time close the strangler as indicated on page 10. STOPPAGE IN PETROL SUPPLY It is advisable at the commencement to assure oneself that the petrol tap is turned on, that there is petrol in the tank, and by unscrewing the petrol pipe at its union, that the pipework is clear of obstruction. It often happens, especially after first fitting, that an air lock occurs in the pipe. This is cured in the ordinary way either by removing and priming same or by the temporary application of air pressure to the filler cap. Vapour locks can also be caused by passing the petrol pipe too near to the exhaust manifold.
DIAGNOSIS OF FAULTS IN THE F TYPE SOLEX (Page 28-30) While the carburettor plays a considerable part in the question of starting, there are also other factors which have a bearing thereon, especially when starting from cold and these should be examined on the following lines:-
BAD SLOW RUNNING If, in spite of trying various auxiliary jets, regular slow running is not possible, excessive induction leakage is certainly indicated, assuming the ignition to be in order and valve timing normal. The engine in this case will not idle regularly and when one attempts to reduce the idling speed, it will generally stall. Air leakage in such a case is confirmed by a depression of the tickler at this moment which will cause a temporary pick-up. One must realise that slow running is in such a case impossible for the engine is actually inspiring via various sources of leakage, a greater quantity of air than that entering via legitimate means, so that the correct slow running mixture becomes unobtainable. Defective magneto is also a most frequent cause of bad idling and the condition of the spark should always be tested before blaming the carburettor and the plugs cleaned and adjusted as above (see previous pages)
BAD ACCELERATION During cold weather one must generally put up with the inconvenience of having to 'nurse' the throttle for the first few minutes after starting. During this time if the carburettor is lightly adjusted, slight strangulation is the best method of avoiding extreme flatness. The strangler, however, should be sparingly used and released as soon as possible. DEFECTIVE ADJUSTMENT Be sure that the adjustment is properly proportioned to the engine's dimensions and that the jets have not been reamered or interfered with. If this is suspected it is best to obtain new ones. If the bad performance is due to an abnormal engine condition, it will generally be necessary to employ bigger jets than those ordinarily required, retaining the same size choke tube. DEFECTIVE IGNITION In the case of battery ignition, note that the accumulators are in order, but where ignition is by magneto one must recollect that the spark intensity diminishes with the speed and as a rule is aggravated by retarding the ignition. When a little weaker than normal owing to slight defects, it is well to set the plug points a little closer so as to offer slightly less electrical resistance to the passage of a weak spark. COMPLETE IMPOSSIBILITY OF ACCELERATION Assuming that starting and idling are possible, then this can only be caused by obstruction of the main jet.
LACK OF MAXIMUM SPEED BAD ADJUSTMENT Check the settings as per table or special directions.
BUTTERFLY NOT OPENING FULLY Note that when the accelerator is depressed fully, the butterfly opens to its greatest extent. This can be checked by observing the position of the limit screw which should be in contact with the boss cast on the outside of the throttle chamber. INSUFFICIENT ADVANCE This is a prevalent cause both of undue consumption and insufficient top speed and can usually be recognised by inability to make the engine knock on a hill when slowing up with fully advanced spark. In such a case, if advancement at the coupling is easy, it is well to try the effect of setting the magneto forward 10 or 15 degrees; otherwise refer to the maker of the car or the nearest Service Station. DEFECTIVE PETROL SUPPLY This can always be recognised by standard acceleration up to certain speed at which periodic hesitations and backfiring occur, curable always by a slight throttle reduction. In such a case remove the float chamber and note the rate of petrol flow from the needle valve which will frequently be sufficient indication. For confirmation, make a special test with an independent test tank placed as high as possible on the car to ensure a good head. SILENCER CHOKED In certain designs of silencers this trouble can easily occur after the car has covered a fair distance. It is generally easy to recognise it by the absence of a clearly marked exhaust note at the tail pipe and instead a steady rush of hot gas. To confirm, make a test with the exhaust pipe disconnected from the silencer.
DIAGNOSIS OF FAULTS IN THE F TYPE SOLEX (Pages 30-31) While the carburettor plays a considerable part in the question of starting and running, there are also other factors which have a bearing thereon, especially when starting from cold and these should be examined on the following lines:-
OVERHEATING It is seldom that the carburettor is the cause of this even in air-cooled engines and it is definitely impossible, strictly speaking, where water cooling is concerned. Too much petrol, or on the other hand, an excessively weak mixture, can certainly raise the temperature a little, but in no case should it nearly approach the margin of cooling that ought to be provided by the water cooling under normal conditions. Apart from a major examination, the most likely directions in which to work are reducing the mixture, but not to an unduly weak condition, and advancing the magneto as far as possible consistent with the avoidance of knocking. A retarded spark will always raise appreciably the engine temperature.
KNOCKING Knocking is similarly the result of various causes which as a rule have nothing to do with carburation, such as pre-ignition due to defective plugs, excessive carbonisation, excessive ignition advance or owing to mechanical noises which can be easily confused therewith, such as loose bearings, worn pistons, etc. When knocking is actually caused by carburation it can only be due to weak mixture and if not curable by one size bigger main jet, other causes must be sought out.
EXCESSIVE CONSUMPTION Note first that there is no leakage either at the carburettor, the pipework or the petrol tank. Be sure then that the estimate of fuel consumption is correct. To confirm this it is always advisable if possible to make a definite test over a known mileage in average country with a measured quantity of petrol, either in the main tank if it is of the type from which all the petrol can be drained, or by the use of an externally placed auxiliary tank. The longer the test of course the more accurate will the reading be, assuming a non-stop run. Never estimate petrol consumption either from the speedometer readings or from supposedly accurate quantities delivered from petrol pumps, either of which are subject to appreciable errors. LOOSE MAIN JET CAP If the heating is sufficient and the jets as small as possible consistent with maximum speed and correct idling, the wastage can seldom come directly from the carburettor excepting through the main jet cap being loose or the jet for some reason not seating on its carrier. DEFECTIVE STRANGLER CONTROL Note that when the control is released during ordinary running, the strangler shutter opens completely.
INSUFFICIENT ADVANCEMENT This is a most frequent cause of heavy consumption as mentioned above and it is always well to run with the spark as far forward as is consistent with the avoidance of knocking. It is well, of course, to note that there is no sign of misfiring and that the carburettor is not flooding, or petrol being lost through other sources of leakage. BAD CONDITION OF THE ENGINE The state of the motor has, of course, a very considerable effect on economy. It is easy to realise that if compression is lost via worn piston rings or pitted valves, quite an abnormal amount of fuel can in some cases be used to obtain a normal performance. An increase of as much as 100 per cent in consumption can easily result from this cause. It is, however, as a rule readily detectable owing to the general lack of power exhibited and in such a case it is useless to attempt to remedy matters at the carburettor.
