SOLEX CARBURETTOR TYPE M FITTING AND INSTRUCTION ...

Choice of the Carburettor . 7- The• choice ofthe carburettor consists in the determination of a suitablediameter. The diameter depends upon the bore andstroke of the engine, the number of cylinders and thespeed at which its maximum power is developed.Generally speaking, however, one can rely upon theinduction pipe, or port diameter being correct for thecharacteristics in question and the carburettor may bechosen accordingly.In speaking of the size of the carburettor we referto the diameter of it's offtake . This should always beequal or slightly larger than that of the induction port.The selection of the carburettor being also very directlyconcerned with the adjustment necessary for the enginein question, we are dealing with it at greater length alittle later on under the heading of " Determination ofCarburettor size ".Position of the Carburettor . — The nextquestion is the determination of the best position inCOUNTERFLANGES OF(CARBURETTORS.4 _ Carburetor' A` B I C, D f E f F G= '~ r26 14813818,512916417173 015314418,5 .1331731 7 18v •,` 3 5 1651501b0,51381891 7 1 9.00 40 7260110,5143931 8 84 6 1 78 62 110, 51 49 1 1 9 10which to mount the instrument . This is generally controlledby the existing induction pipe which can nearlyalways be employed either directly or by the aid ofcounter-flanges which we can supply as per attachedtable .5

It is *dvisable to mount the carburettor in such away that the pipe work is as simple as possible, free fromlocal enlargements and hairpin bends.Provision should also be made to apply a hot airpipe connecting up the air intake of the carburettor to asuitable muffle on the exhaust pipe, excepting in thecase of the horizontal carburettor . Also it is well to seethat the instrument is fitted in such a way that the floatchamber can easily be removed, otherwise the advantagesof accessibility — which is one of the great points of theSOLEX " — is lost.Particularly note also, that excepting in the case ofpressure fed petrol systems, the carburettor must alwaysbe mounted sufficiently low to ensure of perfect fuelsupply in all possible circumstances, and again it is advisableto arrange as far as possible the controls and petrolpipe in such a way that the hand may be inserted underthe float chamber for purposes of its ready removal.As regards the direction of the float chamber, it isadvisable when possible to have this forward.Induction Pipe . — The induction pipe shouldbe as simple as possible and without variations in its diameter,for any local enlargements cause a reduction inthe gas speed at this point and tend to produce backfiringin the carburettor owing to deposition of the suspendedfuel.The pipe should be the same diameter, or slightlysmaller than that of the carburettor offtake . It is veryimportant when fitting to ensure that the port joint isquite free from air leakage, for entrance of air at thatpoint will interfere seriously with starting and slow running.Machined Induction Pipes and Parts forbuilding up Induction Pipes . — To facilitate fitting,we can generally supply a correct pipe which willpermit of the ready adaption of Solex to the majority of6

PARTS FOR MANIFOLD ASSEMBLAGEBend A T Piece TubeDiameter ofCarburettor A B C A B C A B22 & 26 20 35 29 60 30 29 29 2630 20 40 33 70 36 33 33 3035 20 40 38 80 40 38 383540 22 45 43 86 43 43 4340All measurements in millimetres .well-known engines, a list of our prices for these fitmentsbeing supplied on demand . In the case of other typesof engines for which we do not stock complete pipes,we can provide corners, bends, and tubes as per the attachedtable for each size of carburettor.Support . — In orderto prevent vibrationin cases where the inductionpipe is long and notvery rigid, it is well tofix the carburettor to aconvenient portion of theengine by means of alight but rigid strip ofsteel which can be attachedto one of the flangebolts . This is only forthe purpose of ensuringFig . 3against horizontal vibrations,the induction pipe itself being invariably sufficientto bear the weight of the carburettor.Throttle Control . — This is obtained by meansof an abutment plate (fig . 4) mounted on the flattenedend of the throttle spindle.7

The abutment plate carries a screw limiting themaximum opening point (fig . 4) and it is firmly fixedby means of a springwasher . A screw for theregulation of slow runningis also mounted onthe other side of theabutment plate . In additionto this, a locatingFig . 4pin is centrally placedand articulates with aseries of holes arranged at 45° from each other at theend of the throttle lever so that the latter can be mountedin a variety of positions.The lever is normally mounted on the left side lookingtowards the air intake in the case of MV type enginesand at the upper part in the case of the MH type.In certain cases it is necessary to have the control at theright side for MV carburettors and at the lower part inthe case of MH instruments.In such a case, remove the abutment plate from thespindle and interchange respectively the opening limitscrew with the slow running adjustment screw . Theabutment plate will then take the place of the packingwasher that will be noted on the other end of the spindle.When drilling thethrottle lever for attachmentof the control rod,note that the radius isrte,equal to 3/4 of the travel, -as per attached diagram.To facilitatethe Fig . 5mounting of the controltod, we can supply ondemand a ball joint whichgives a minimum of play and a maximum of freedom inthe control.It is advisable to have as few joints as possible betweenthe accelerator pedal and the throttle lever, for amultiplication of articulated joints here represents in theaggregate a good deal of play in the control when theycS

ecome worn . In cases, however, where this is unavoidablethe best method of guarding against such troubleis to arrange a pull-off spring to operate directly on thethrottle lever, so that the various worn surfaces are inconstant thrust and the play thus taken up.Petrol Union and Filter. — To join up thepetrol pipe with the union, it is only necessary to solderthe former into the -swivellingportion of the union.Our carburettors are all deliveredas standard with afilter which is placed in theswivelling part in questionand the latter is drilled totake a petrol pipe of 8 m/aexternal diameter. We cantherefore supply piping ofthis size if required.Fig . 6The filter is placed atthe upper part of the floatchamber and is therefore very accessible, and the operationof removing and cleaning the gauze is quite a triflingone . It is to be noted that this device is not of the" decanter " order, for the design of the float chamberis such that any water which passes through remains atthe base of the chamber and cannot enter the main jetchannel until a considerablequantity has accumulated,when it can be quickly emptiedon dismounting the floatchamber, an operatidn whichcan be conducted muchmore quickly than by dismemberingthe filter.To adapt the filter to acarburettor already fittedFig.7with a simple swivellingFitting indirect Filterunion, we have provided aslightly modified form which we describe as an " indirect " filter that can be adapted to the existing unionwithout any soldering (see fig . 7).To obtain a correct petrol supply, it is always advisableto give a mean inclination of at least 10 010i to thepetrol pipe between the tank and the carburettor.9

Easy Starting device . — Some engines whencold present a little difficulty in starting, especially withheavy fuels and with Benzol, thus demanding a muchgreater turning effortand a temporary richmixture. Furthermore,the general use of electricalself-starters necessitatesthe provisionof some means of easystarting so as to savethe battery as much aspossible. To cater forthese necessities and Fig 8ensure immediate startingin the case of obstinateengines we have devised a special arrangementwhich is attached to the air entrance and controlled bymeans of a shutter . The latteris kept in the fully open positionby a spring when the engineis running and as it mustbe controlled both at the startinghandle and from the dashboarda double ended lever isfitted, drilled at each end.The starting arrangementFig . 9 W for the MH type takes the formof a modified bell (see fig . 8) . That, however, for theMV is made in two designs . A short one (fig. 9) isFig . 10fitted where no hot air is required, but the longer one(fig . 10) is additionally provided with a register for theadmission of cold air. These two types • can immediatelybe attached to the carburettor by means of an ordinaryclip joint .10

It is to be noted that the air shutters for the MVtype can be mounted on the MH carburettors in caseswhere it is desired to apply hot air to this model.Control . of the Easy Starting device . —To facilitate this, we can provide a special serrated knobthat can be m'-anted on the dashboard and attached bymeans of a multi-strand steel cable to the air shutterlever .Heating . — The horizontal type, which attainsits heat directly by conduction from the cylinder blockis, as a rule, sufficiently heated without any extra applicationof hot air, but in the case of the vertical carburetorit is usually necessary to provide for external heatingand generally desirable to make this controllable bymeans of an air register, so that adjustments may bemade for climatic changes.In the " Solex ", the heating is carried out entirelyby air, no form of hot water jacketting being includedin any of our carburettors,Hot air is obtained by means of a muffle mountedon the induction pipe and is led to the carburettor by atube either flexible or otherwise, as per figure 12.It is not necessary to solder the attachment, for wecan provide a clip joint that will enable this to be donewithout any mechanical work.It is necessary always to guard against any restrictionin the volume of air provided, for unless absolutefreedom is assured here, the engine power is bound tosuffer .It

When fitting the muffle, note carefully 'that thereis ample air space for perfect volumetric freedom . AnyFig . 12restriction here will result in loss of power and economy.Swivelling Air Intake . — To facilitate thefitting of the hot air pipe to the carburettor in caseswhere its direct entrance is inconvenient, we supply aswivelling air bendwhich will take upFig . 13any required positionon a horizontalpiane . It may bemounted either dire.. tly on the carburettoror on the offside of the air shutterwhen such is fitted. In the former case, a nipple is provided for adaptionof the shutter to the clip joint, as per sketch .Flange Governor Throttle . — To facilitatethe fitting of carburettorsto engines ,equippedwith a governer, we providea special throttleembodied in a modifiedflange member which ismounted between the carburettorand the inlet portor pipe, and can be joined?ig . 14up directly to the governor.12

IIADJUSTMENTOF THE CARBURETTORThe adjustment of the SOLEX consists in ; —1st . The selection of an auxiliary jet " g " whichwill give the best idling, and —2nd . A main jet which gives best power and acceleration.These adjustments can be quickly made owing tothe extreme accessibility of the lets.The correct size of choke tube is determined fromthe table of adjustments further on.DISMOUNTINGIn order to dismount the carburettor for tuning orcleaning, it is only necessary to unscrew the large nut" E " when the float chamber can be withdrawn givingimmediate access to both jets without breaking a singlejoint, losing a drop of petrol, or requiring any form ofspecial key.When remounting, it is only necessary to see thatthe members are registering correctly when the assemblageis completed by moderately tightening thenut"E".SLOW RUNNING ADJUSTMENTFig . 15Auxiliary Jet " g "When the butterfly is in anapproximately closed position, asshown in figure 17, the mixtureis supplied by the auxiliary jet" g " . This jet is provided witha slot to enable an ordinary screw driver to be usedthereon, and is stamped on the upper part with a numberindicating the diameter of its spraying orifice in hundredthsof millimetres.13

Do not in any circumstances, reamer or interferewith this orifice.The slow running adjustment has nothing to do withthe power setting and can be undertaken with the car atrest .The adjustment is carried out in two ways ; —''IIIIIIIIIIIIIIIIIIIIIIIIIItlIIIIiIiIooFig . 161st . Mixture Regulation . — Consult first thetable of adjustments and commence by inserting the jetindicated for an engine of corresponding dimensions.Excess of fuel is recognised by ; —a) A rhythmic surge popularly described as " hunting" .b) When the engine gradually slows and stops.petrol will drip from the carburettor on opening thethrottle .14

c) The plug points will be coated with soot . In thiscase, reduce the auxiliary jet by one size and try againuntil perfectly regular idling is obtained.Insufficient fuel is recognised by ; —Difficult starting and irregular firing, the latterbeing temporarily cured by depressing the tickler.Fig . 17It is well to note the idling when the engine is atits full working temperature before finally deciding, for,heat will always enrich the mixture.2nd . Throttle adjustment for idling . —This is undertaken by the regulation of the throttle adjustingscrew on the abutment plate.15

Screw inwards to increase the idling speed and outwardsto diminish it.ADJUSTMENT FOR POWERFirst of all, see that the choke tube is of correct sizefor the engine as per table of adjustment on pages 18and 19 . To remove the choke tube, dismount the floatchamber and unscrew the small fixing screw when thechoke can be withdrawn with the fingers.Numbers indica -ting the size of carburettorand the internaldiameter of the waistwill be found casttherein.The approximatesize of the choke havingbeen established,refer now to the tableand fit to commencewith the jet indicatedfor a given choke andengine capacity.Owing to the variablecharacteristics ofengines and the differentspeeds at whichthey are designed togive their maximumHP . It is only possibleto approximateFig . 18 . — Main Jet.theoretically the choke and jet sizes necessary . These mayrequire to be varied up or down according to conditions.1-6

Broadly speaking, the higher the maximum enginespeed and the greater the valve and induction area, thelarger will be the choke size necessary and vice versa,the main jet size being in each case experimentally alteredto suit.To change the main jet unscrew the cap with anordinary spanner when it can immediately be removedwith the fingers, no joint being broken and no fuel lost.To re-assemble the jet member, replace the jet andscrew down the jet cap with moderate tightness.Excessive force either here, or in assembling the floatchamber is unnecessary, and will damage the carburettor.SELECTION OF THE CORRECT SIZEOF THE CARBURETTOR1st . Horizontal or Vertical,The former is suitable for monobloc engines with asingle inlet port and sufficient head of petrol to ensureunfailing supply under all conditions . The latter canbe fitted to all engines without exception if a suitableinduction pipe is provided.2nd. Choice of Diameter.The number of the carburettor indicates the internaldiameter of its offtake in millimetres and the correct sizecan be determined from the tables when the bore, stroke,and speed of the engine are known.(See examples bn page 20 .)17

Table of settings for SOLEX Carburettor, type MVTheoretical Diameter of Choke tube K.TABLE 1Number o1 R . P . M..,4o,,M,M —EMMA80 15•• 15 15 76 16 >~ 17' 18 79 1955 •• 15 16 96 17 17 18 19 19 20• >6 16 1 1i~ 18 18 ' 19 20 20_ . >6 16••>6 16 1~ 18 18 192017 1777 1819 19 202021•• >6 17' 17 18 18 >9 • 20 20 2060 ' 16 17' 78 18 19 29 • • 21 21 22• 17 17 18 19 19 20 20 21 21 22 22_ 18 18 19 20 . . . . ..•• 17 1/ 18 >8 19 19 20 0 21 21 22 ~• >7 78 19 19 20 20 22 22 2365 • 18 >8 19 20 20 21 22 23 24• 18 19 19 20 2> 21 23 23 24]_ -• 18 19 20 21 21 22 24 24 25•• >2 18 19 19 20 20 22 22 23• . 18 19 212312322470 ' 78 19 221 0 21 2212 2Z2 2 223 2 4 25• 19 20 • 21 22 1 23 23 24 24 125 26• 19 j 20 22 _231 23 124 3?5 25 26 2L•• 18 119 20I 21I 21 22 23 23 124 24;• 19 19 20 2122'22 23 23 2425 26!175 • 1 .9 20 21 22 22 23 24 24 25 26 27'• 20 21 21 22 23 24 24 25 26 26 27• 20 21 22 2 .3 24 24 25 J 26 II. 27' 28'• 19 20 21 22 _23 23 24 25 25 ' 6 27'• 20 21 22 23 24 24 25 25 26 27' 2880 • 20 21 22 23 24 25 26 26 _2!. 28 29• 21 22 23 24 25 26 26 27 28 29 301• 22 23 24 25 26 26 2 28 29 30 ~1• 20 21 22 23 24 24 25 26 2/ 28 28121 22 23 24 25 25 262/ 2/ 28 2.9483 • 21 22 23 24 7. 5 26 27' 28 2913031• 22 23 24 2 5 26 22' 28 29 29 1 30 3123 24 25 26 27' 28 29 30 31 32 33• 21 22 23 24 25 25 26 2/ 28 29 30• 22 23 24 25 26 26 2/ 28 29 30 3190 • 22 23 24 25 26 27 28 29 30 31 32,• 23 24 25 26 27' 28 2.9 30 31 32 331• 2 t 25 26 ,2/ 2,5' 29 30 31 32 33 34Number of R . P . M./coo /200 1400/6G0 /800 2,00122002'+4002600 2BO6>?O 20 21 23 , 24 , 25 26 21,28 29 30>30 21 22 23 _24 26 27' 28 29 30 3195 140 21 23 24 25 25 28 29 30 31_32>5022 23 25 26 2/ 28 30 31 32,33_ 160120 22 2427 22 2523 27'2S26 28 29-77 3028 31 .3229 30 3133>3021 23_24 25 2/ 28 29 30 31_32>00 140 22 23 25 26 28 29 30 31 32_33,>50 22 24,2G 21 28 30 31 32 33 34e few1220 23 2527 23 2624 2826 29 30 3221_28 29 33 34 3530,31 32130 22 24 25 26 28 29,30 31 32 331o5 >4623,24 26 2/ _ 29 _30 31 32 33 34, ,>50 23 25 2/ 28 30 31 32, 33 34, 35_ 160 24 26 _L 29 30 32 33 34 35 36>2022 24 25 27' 29 29 30 31 32 33230,23 25 26 28 29_30 32 33_34, 35110 >40 24. 25 27' _28 30 31 33 34 35 36150 24 26 28 29 31 32 33 35 36 3J'>60 25 27r 28 .30 32 33 35 36 31" 38120 23 25 26 28,29 30 32 33,34 35130 24 25 2/ 29 30 31 33 34 35 .36'125 140 24 26 28 29 31 32 34 35-3636 37'150, 25 2/29 . 30 32_33 35 36_37 38>6o 26 28 29 31 33 3 , 36 38 IL>3024 26 28 30 31 33 34 35 36 3824o 25 21 29 31 32 34 35 36 38 39>P• 150 26 28_30 32 33 35 36 31,39 40160 21 29131_32 34 36 37' . 38_ 40Lo Z7 29 31 33 35 3f 38 40 _/46 26 28 30 32 33 35 37 38_39 40150 27 29 31 33 34 36 38 39_402235 260 27' 30,32 34 35 37' 39 4022'0_28 30 33 35 36 38 40180 29 31 33 35 37' 39 40 _/4o 22' _29 . 31 33 35 1 36 38,4(o/50 28 30 32 34 36 ' 3/, 39 40/30 /6028 31 33 35 37' 38,4o>To 29 31_34 36 38 40 _ _180 30 32 35 3r 39 4dChoice of Sizeof CarburettorThe choke tube being determinedby table n . 1, thesize of carburettor can bearrived at by the table n . 2hereunder.TABLE N . 2Choke tube K15 to 1819 to 2122 to 2526 to 2930 to 40Sizeof Carburettor2630354046DETERMINING1 . MAIN JETTABLE N . 3ChokeKJetGChokeK .JetGChokeKJetG15 50 24 110 33 17016 65 25 115 34 18017 75 26 120 35 18518 SO 27 130 36 190119 85 28 140 37 20020 90 29 145 38 20521 9 5 30 150 39 21022 100 31 155 40 22023 105 32 16048SIZE OF. JET2 . AUXILIARY JETDetermine by experimentthe slow running jet, notingthe table n . 4 hereunderand according to the sizeof carburettor fitted.Carburettor2630 or 3540 or 46TABLE N . 4AuziliarJ jet45-50-5555-60-6560-65-70

Table of settings for SOLEX Carburettor, type MKTheoretical Diameter of Choke tube K.TABLE 1Number of R . P . M..8 .n .100 /6'00 MOO X)002200 24001tAO0 d1IX 3006.32GC..340080 - - — 12 12 13 1314 15 15 1690 12 12 13 14 14 15 16 16 17'.55 100 12 >P 13 14 1S 15 16 17 13 181/0 12 12 13 14- 15 16 16 1~ 17 18 191,2o 12 13 14 14 15 16 17 17' 18 18 1990 12 13 14 14 15 16 16 1}' 17' 18100 12 13 14 15 16 16 17' 18 _18 19 2060 11 . 13 14 15 15 16 1T 18 18 19 20 2112 . 13 14 15 16 11 18 18 19 20 20 21130 >4 18 16 18 18 19 20 21 21 2210 . 13 14 -15 16 17 17' 18 19 19 20 21110 14 15 16 17' 18 18 19 20 20 21 2265 12• 15 16' 11 18 19 19 20 21_21 22 23230 15 16 17' 18 19 20 21 21 22 23 2414• 16 17' 18 19 2o 21 21 22 23 24 25/00 14 15 16 17' 18 19 -19 20 21 22 23110 75 >6 17' 18 19 20 21 21 22 23 2470 >2'0 16 17' 18 19 20 21 21 22 23 24 25130 16 18 19 20 21 22 22 23 24 25 2614 . 17' 18 20 21 22 22 23 24 25 26 27200 15 17 18 19 20 20 21 22 23 23 24120 16 17 19 20 20 21 22 23 23 24 2575 120 1 18 19 20 21 22 23 24 25 25 26130 18 19 20 21 22 23 24 25 25 26 26— 140 : 21 22 23 24 21S 261/0 19 20 21 22 23 23 24 25 26 27'/20 8 19 21 22 23 23 24 25 .26 2q 2.880 230 - e 21 23 24 24 25 26 2~' 28 29_ 140 0 21 22 23 25 25 26 27 28 29 30150 20 22 23 24 25 26 21 28 29 30 31280 13 . 21 22 23 24 25 26 2E 27' 28f2• 19 21 22 23 24 25 26 2Y 28 29 3085 130 ' 23 24- 25 26 2/,28 29 30 31140 21 22 24 25 25 21 28 29 30 31 32250 22 23 24 25 2 28 29 30 31 32 33/to • 22 23 24 25 26 21 28 29 30>2• 20 2Z 23 24 25 26 2 23 29 30 3190 230 2-1 23 24 25 26 27' 28 8 29 30 31 3224 . 22 24 25 25 2 28 29 30 31 32 3325o 23 24 26 Z 28 29 30 31 32 33 34Number of R . P . M.m '^ t000 1100 ~f7oo /600 /goo tOOGd"0,01~60r'26001.8c oG>zo 18 20 22 23 24 20 27' 28 29 3023o >9 21 22 24 25 27' 28'29 30 3195 •• 20 22 23 25 26' 28 29 30 31 32. 20 22 24 26 27' 29 30 31 32 33— .' 21 23 25 .2 28 29 31 32 33 340 19 21 23 2 26 28 29 30 91130 20 22 24 25,2X .28 29 30 31 32,100140 21 23 24 26 28 29 30 31 32 33150 21 23 25 2Y 29 30 31 32 33 34260 22 24 26 28 30 31 32 33 34120120 22 24 25 27 28 30 30 31 32130 21 23 25 26 28 29 31 32 33 34Jo 140 22 24 26 27' 29 30 3Z 33 34250 23 25 21 28 30 31 33 34— 160 23 25 ...21' 29 31 32 34>30 21 23 25 27 28 30 31 32 33 34130 22 24 26 28 29 31 32 33 3411/>o>40 23 25 27' 29 30 32 33 34,1.50, 24 26 28 30 31 33 34>60 24 27' 29 31 32 34 _f2' 22 24 26 28 29 31 32 33 340 23'25 27' 29 31 32 33 3411 /4 . 24 26 28 30 32 33 34r5o 25 27' 29 3.1 39 342132 32 34 _ — _230 24 26128 30 .32 33140 25 27' 29 31 33f,2 . 150 26 28130 32 34.• Z' 2931 3322' 30 32 34 _ _'. 26 28 30 32 3427' 29 31 33 _12 • . • 28 30 32 34• 28 31 33293234_. 21 29 31 34 — —• 28 30 321 3 0 . . 29 3-1 3 3170 29 322_ f3 3033__2Choice of Sizeof CarburettorThe choke tube being determinedby table n . 1, thesize of carburettor can bearrived at by the table n. 2hereunder.TABLE N . 2Choke tube 112 to 1819 to 2122 to 2526 to 2930 to 40Siteof Carburettor2630354046ChokeKJetGDETERMINING1 . MAIN JETTABLE N . 3ChokeKJetGChokeKJetG12 60 22 110 32 17513 65 2 3 115 3 3 18014 70 24 120 34 19015 75 25 125 35 19516 80 26 130 36 20017 85 27 140 37 20518 90 28 150 38 20519 95 29 160 39 21020 100 3 0 165 40 2202021 105 3 1 17019SIZE OF JET2 . AUXILIARY JETDetermine by experimentthe slow running jet, notingthe table n. 4 hereunderand according to the sizeof carburettor fitted.Carburettor2630 or 3540 or 46TABLE N . 4Auxiliary jet45-50-5555-60-6560-65-70

From these three factors the choke tube size maybe determined by consulting table No I.The size of the carburettor follows from No 2 andthe approximate jet sizes necessary are shown in No's 3and 4 . When doubtful, choose a carburettor having anafftake diameter most closely corresponding with that ofthe inlet port or induction pipe.First Example : A four cylinder engine 80 x 120either monobloc or cylinders cast in pairs.Maximum speed 1 .600 r. p . m ., induction diameter28 m/m . The table on page 18 indicates a 21 choke, whichestablishes the carburettor size as 30 m/m•In this case, one would therefore fit a 30 MV carburettorwith a 2i choke, a main jet of 95, and an auxiliarywhich may vary between 55 and 65.Second Example : A four cylinder engine90 x 140 monobloc with one inlet port and an enginespeed of 2 .200, and an induction diameter of 40A 40 MH is indicated here if petrol head permits.The choke will be 27 and the jets 140 main with an auxiliarybetween 60 and 70.For two cylinder engines, the theoretical diameterof the choke should be reduced by one number and themain jet by two or three numbers.For six cylinder engines, with a single carburettorit is necessary on the contrary to increase slightly thesizes of the choke and main jet.For six cylinder engines, having their cylindersarranged in groups, it is better to have a carburettor pergroup, for, otherwise it may be difficult to get perfectdistribution.For six cylinder engines, having a special inductionpipe centrally divided and taking two carburettors or adual instrument, treat each group of three as a separatefour cylinder engine .20

IIIDIAGNOSIS OF FAULTSNo question can arise as to the unsuitabilityof the carburettor if the correct type has beenselected . It is solely a matter of correct fitting andadjustment.Always conduct diagnosis methodically and neverdo two things simultaneously, for, it will then be impossiblecorrectly to locate the effect of the alteration.Remember that the carburettor is a precision instrumentand must not be roughly handled.Avoid always any form of structural alteration for,every detail of design has been carefully thought out,and, in endeavouring to improve the instrument one ismuch more likely to damage it permanently.FLOODINGThe Solex has four washered joints ; —The Main jet carrier, J1.The Needle valve seating, J2.The nipple and union joints in the supply system,J2 and J3.The last two mentioned, being exterior fittings caneasily be examined and tightened if loose, any leakage,however, from the needle valve joints will resolve itselfinto a drip at the base of the main jet carrier and givethe impression of incorrect level . The first thing, therefore,is to assure that all these joints are perfect.21

Grit in the Needle Valve . — This is offairly frequent occurrence when the motor or carburettoris new and is due to pieces of solder, copper oxide, etc.from the petrol pipe becoming lodged in the needleseating or guide . It is easy .to dismount and clean thevalve, but be careful to use a well fitting spanner in sodoing, otherwise the guide may be damaged.Punctured Float . — Should this happen, theincreased weight of the, float can easily cause floodingthrough high level . It is preferable in this case toreplace the float ; if one has the facilities, however, thepuncture can easily be cured with a small application ofsolder. If this is undertaken, get rid first of the containedpetrol by immersing the float in boiling wateruntil all the bubbles cease.Level too high. — The simplicity of theconstant level arrangements make this extremely rare butit can occur unless light fuels are used in a carburettorhaving a benzol float or wide needle seating, and thecure is to change the float for one of correct weight oruse a smaller needle seating.The weights of the floats for .730 petrol are asfollows; —33 grammes for 26 m/m carburettors.42 30 >64 35 and 40 carburettors.110 46 and 25m/mWe can also supply special benzole floats of whichthe weights are as follows ; —47 grammes for 30 m/m carburettors.70 » 30 and 40 m/m carburettors.To check the petrol level . — This operationis quite simple . It is only necessary to dismount thefloat chamber, take out the main jet, leaving the carrier22

in position and remount the chamber with this memberexposed at the side instead of in its proper position . Onturning on the tap, the fuel should now rise to within3 m/m of the top of the carrier.Too much pressure. — When an autovac isfitted, or, if the head of petrol is fairly normal, the26 m/m carburettors have a needle valve seating of 2 m/-diameter and the larger types of 30 /m, 35 m/m, and40 m/m, have a 2 .5 1/m seating, but when the petrol ispressure-fed, or has a head of 6 or 8 feet, the buoyancyof the float may be insufficient to close the needle againstthis weight of fuel, and in this case slightly smallerseatings should be fitted . We can supply these onrequest .DIFFICULT STARTINGIt is easy to test whether the petrol is comingthrough by depressing the tickler, when if there is petrolin the float chamber it will be possible to feel the float.If one cannot detect its contact with the tickler andcannot cause flooding by depression of the latter, it isthen evident that the float chamber is empty . In thiscase, see that the petrol tap is turned on, that there ispetrol in the tank, and finally, by unscrewing the petrolunion, that the petrol pipe is clear.After first fitting, it occasionally happens that thepipe becomes air locked . If this is found to be the, caseit must be primed in any convenient way.Instances are also known in which an equivalentcondition can be produced by the pipe passing too closeto the exhaust manifold when a vapour pocket can beformed and interferes with the flow.23

Level too low . — When benzol or heavy spiritis used in a carburettor set for light fuel, this can easilyhappen . The best cure is to have a heavier float or insome cases the required correction can be effectedby putting in the original float upside down, which raisesthe level about 3 /m.Auxiliary jet too small . — Increase graduallythe size of the jet till the required performance is obtained,but first be sure that the original one was not stoppedup.Throttle opened unduly or insufficiently.— In order to exercise the strong suction on the auxiliaryjet necessary for starting, the Throttle must bealmost closed . If the carburettor is now flooded it isquite possible when in this position to get a few explosionsfollowed by stopping . This is due to over-richnessand insufficient volume. Open slightly the throttle.Air Leakage . -- Difficult starting always resultsif there is air leakage at anv point of the inductionsystem — port joints, carburettor flange joint, or worninlet valve guides.Wear in the throttle spindles of very old carburettorswill have a similar effect . The depression on theauxiliary jet is thus reduced to the point where its restrictedoutput is insufficient to carburate the additionalair that leaks in . Opening the throttle a little wider withadditional flooding will generally allow a start to bemade, the auxiliary jet size being also increased a littleif necessary.It is however, always advisable to locate and curethe leak at the earliest opportunity, for, good idling willotherwise be impossible .24

Ignition faults . — It is always well before blamingthe carburettor to be sure that the starting spark isof sufficient intensity . Remember also that manymagnetos will not spark efficiently at low speed unlesswell advanced . If there is anv doubt about the switch,remove the earth wire . See that the contact breakerpoints are clear and open to .4 % and that the plug electrodesare also clean and separated to .6 % . The correctuse of the air strangler will always ensure-easy startingif the ignition is right, regardless of carburettoradjustment . (See page 10 .)BAD SLOW RUNNINGIf, in site of careful auxiliary jet adjustment it isstill impossible to get good slow running, air leakage ispractically assured . To confirm, slow down as much aspossible without stopping, and flood the carburettorslightly when the engine will speed up temporarily.The same remarks apply here as in the case of difficultstarting and the leakage must be stopped before goodidling is possible.BAD, ACCELERATIONDuring cold weather, one must understand that it isnot possible to get acceleration immediately after startingup, but it should be possible after running a few minutes.Insufficient Heating . If inefficient accelerationpersists even when the engine is fully warmed,defective heating is indicated . Examine the arrangementstherefore to locate the shortage . See if the muffleis large enough and embraces a sufficient area of hotexhaust pipe to collect the desired degree of heat andvolume of air .25

Bad Adjustment. — Try a larger main jet" G " and if still bad reduce the choke size to one sizesmaller ; at same time verify from the tables that it isapproximately correct.Bad Ignition . — It is never advisable to attemptbrisk acceleration when too much retarded, for the lowmagneto speed will not produce an efficient spark underthese conditions.Similarly, if the plug gaps are too wide, the compressionresistance opposed to the passage of a weak sparkduring acceleration can easily defeat the magneto andgive the impression of bad carburation.Badly designed Induction Pipe. — In manycases engines are incurably, sluggish owing to the inductionpipe being too large or of bad shape. The formerwill cause bad acceleration by providing insufficientvelocity to keep the fuel in suspension and the latterwill have the same effect owing to unequal distribution.The best test for latter is by noting the colour andcondition of the plug electrodes.They should all be identical and if not bad distributionis indicated and a more suitable pipe should befitted .Total Absence of Acceleration .— When allattempts to open the throttle result in a complete failureto fire at all, the main jet is either stopped up or grosslytoo small.DEFECTIVE SPEED ON THE LEVELBad Adjustment . — .Verify the sizes of thechoke and jet from the table and try larger ones of each.26

Throttle not opening fully. — Verify thatwhen the accelerator pedal is fully depressed the limitscrew on the abutment plate is up against its stop fincast on the body of the carburettor.Volumetric Restriction . — Examine the hotair arrangements and see that at no place is the area lessthan that of the carburettor off-take . It should at allpoints be a little greater than the latter.Carburettor too small . — This is easy toestablish by trying larger chokes . If the speed improvesup to the largest choke supplied for that size - (a mainjet to suit being used in each case) a larger carburettoris indicated.Retarded Ignition . — Try a slight advancementor have the timing checked by a competentengineer.Shortage in fuel supply . — This trouble isindicated by good acceleration up to a certain speed atwhich an irregular hesitation sets in, accompanied veryoften by slight back-firing in the carburettor.Confirm by a short run on a separate test tank placedso as to insure a good head.Too much Induction Heat . — This is a prolificcause of bad high speed performance . Make a comparativetest with the heating reduced or with the bonnetoff .Choked silencer .— With certain kinds of silencers,this also is a frequent cause of speed losses . Confirmby a short run with the silencer off or disconnected.27

OVERHEATINGIt is very seldom that overheating is due to carburation; with a well designed engine it would be an impossiblecause, for the adjustment would have to be so badthat other troubles would be noticed before overheating.Defective cylinder casting, water circulation, or aircirculation are the usual reasons for overheating.The temperature is raised a little by either too lightor too heavy a mixture and a retarded spark will have asimilar effect, but these can always be ruled out in a badcase of overheating .KNOCKINGThe only condition of adjustment that can causeknocking is weak mixture . If a larger jet does not cureit one of the many other causes must be sought out.The most usual are ; — detonation, excessive sparkadvancement, carbonization, worn bearings, loose pistons,etc.EXCESSIVE CONSUMPTIONExamine the carburettor and supply system first forleakage . Then take steps to assure oneself that theconsumption figure has been correctly estimated bymaking an out-and-back run over a milestoned route withan accurately measured quantity of petrol . Do not relyon petrol cans, for their contents are not guaranteed, noron mileage indicators, which are frequently inaccurate.For preference make a non-stop run over about 40or 50 miles . For a more accurate measurement still agraduated test tank should be used.28

Bad Adjustment . — If the choke is well chosenand the smaller jets used with which sufficient power andadequate slow running are obtained, the the trouble isnot due to carburation.See that there are no signs of flooding and that themain jet cap is properly tightened.Defective Heating . — In induction heatingarrangements are absent or insufficient, consumption willalways suffer, for unduly large jets must be used to geta standard performance . In this connection it is well tomention that final adjustments should always be madewhen the engine is at its full working temperature.An engine that will pick up immediately from cold4 sure to be wasteful when hot.Retarded Ignition .cause of waste.This is a most commonIf the ignition is adjustable, always run with itadvanced as far as possible consistent with the avoidanceof knocking . If the engine cannot be made to knock,undue lateness is indicated, and it would be well to havethe magneto timing checked.Bad condition of the engine .— The state ofthe engine has always a great bearing on consumption . Ifpiston rings are not gas tight and valves do not seatproperly much efficiency is lost both on the compressionand on the firing stroke . Weak exhaust springs, excessivetappet clearance, and in many cases actual bad valvetiming are other and most prolific causes of waste forwhich the carburettor becomes the scapegoat.Remember, however, that after these defects havebeen remedied, adjustment is nearly always necessarybefore the full advantage of the overhaul is obtained.29

TROUBLES CAUSEDTHROUGH DEFECTS IN AUXILIARYSUCTION FEED FUEL SYSTEMA great number of engines are now provided withthis type of petrol supply, and it is well to point out sometroubles that can arise therefrom.1. Leakage will readily result if the pipe connectionsbetween the tank and the induction system are nottight and this will always cause bad slow running anddifficult starting.2. It occasionally happens with certain types of instrumentsthat a small quantity of petrol passes via theexhaust pipe into the induction system, and when thisoccurs defective running and heavy consumption willtake place.3. After a long run with fully opened throttle thepipe diameter or, as the case may be, the degree of inductiondepression may be unequal to maintaining a fullpetrol supply, especially on ascending a hill . In sucha case misfiring will take place accompanied by poppingin the carburettor, and unless the throttle is temporarilyclosed for a few seconds the engine will stop.In order to check the efficiency of the vacuum operatedsupply, remove the connection in the inductionpipe and carefully plug the hole . The tank will functionas an ordinary gravity tank and should maintainfull engine power so long as there is any petrol left therein.If in these circumstances the engine functionsproperly, the carburettor may be absolved from blameand the makers' booklet relative to the auxiliary tankconsulted .30

"SO LEX" CARBURETTORS "M" TYPEPRICES OF CARBURETTORS & SPARE PARTSCarburettor completeHorizontal or Vertical with filter.REDUCED PRICESSIZE OF CARBURETTORS26 % 30 /m 35 % 40 46-%£ 5 .0 .0 £6 .0 .0 £ 7 .0 .0 £8 .0 .0Butterfly5/6 6/- 6/- 7/- 8/-F Butterfly Spindle 5/6 6/- 6/6 7/-Screws for Butterfly, per pair . 1/- 1/- 1/- 1/-7/61/-11 Butterfly complete with Spindle a Screws 12/ - 13/ - 13/6 15/ - 16/6Dr >4 G Parts fixed on Butterfly Spindle(Standard on all Solex "M' Type) 8/6 8/6 8/6 8/6 8/6w Butterfly with Spindle completep,',2 with all part 20/6 21 /6 22/- 23/6 25/-tn Throttle Chamber with Boat chamber top £2/ 5/0 £2/17/6 £3/ 6/0y£3/16/0 £4/16/0. Body of Carburettor complete . £3/ 5/6 £3/19/0 £4/ 8/0 £4/19/6 £6/ 1/0Float Chamberless Jet S and. . central stem£ 1 /10/0 £ 1 /16/0 £2/ 2/0E2/ 6/0 £3/ 2/0t Butterfly 5/6 6/- 6/- 7/- 8/-Butterfly Spindle 5/6 6/- 6/6 7/- 7/6Screws for Butterfly, per pair . 1/- 1/- 1/- 1/- 1/-e F Butterfly complete with Spindle and Screws 12/- 13/- 13/6 15/ - 16/6Parts fixed on Butterfly Spindle" (Standard on all Solex "M" Type) 8/6 8/6 8/6 8/6 8/6u Butterfly with Spindle completed awithal' part, £1/ 1 / 6 El/ 1 / 6 £1/ 2 / 0 £ 1 / 3 / 6 El/ 5/00 Throttle Chamber with hat chamber top £2/ 2/6 £2/18/6 £31 7/6 £3/17/0 £4/16/0Body of Carburettor complete . £3/ 4/0 £4/ 0/0 £4/ 9/6 £5/ 0/6 £6/ 1/0yFloat Chamber with central stemless Jet Stand £1/ 5/0 £1 /10/0 £1 /14/0 £1 /16/0 £2/10/0Air Bell without Strangler . . 10/6 13/6 17/6 £1 / 0/0 £1 /15/0Choke Tube "K" 4/6 5/6 7/6 9/- 10/6Float "F" 5/- 5/- 6/- 6/- 8/6Air Strangler complete (Horizontalor Vertical) 18/6 19/6 £1 / 0/0 £1/17/6 £2/ 5/0Fixing Collar for Body of AirStrangler complete with screw &bolt 3/6 3/6 4/6 5/- 5/6° Counterflange with washer and 2 bolts 6/ — 6/- 6/6• u Flange Washer 1/- 1/ . 1/67/6 8/6. Flange Bolt -/6 -/6 -/9 -/9 . -/9y Bend 7/6 8/6 12/6 15/-Teepiece 7/6 8/6 12/6 14/-E Copper Tube 12" Length 7/- "7/6 12/6 14/-.. Copper Tube 20" Length 13/6 14/6 £1/ 0/0 £1/ 2/0eAir Strangler with register andfixing collar for Flexible tube • 18/6 £1 /12/6 £1 /15/0 £2/ 0/0 £2/ 5/0o Hot Air Bend 9/- 10/6 12/- 13/- 16/6x 9 Register for cold air 4/- 4/6 5/- 5/6 7/6w Ctb0Tube for Union2/9 3/- 3/6 4/- 4/6M Flexible Tubing for Hot Air, per foot 2/6 2/6 3/- 3/- 3/6a Fixing Collar for flexible tubewith bolt and nut 3/6 3/6 4/6 5/- 5/6Flange Governor with ? washersa g bolts £1 /12/0 £1/15/0 £1 /17/6 £2/ 2/6Bolt for above -/9 1/- 1/- 1/6Washer for above -/9 1/- 1/- 1/6Name Plate . -/6 -/6 -/6Dismounting Nut .6/-. • •6/- 6/- 6/ - 6/-NOTE. — 26 '/m MFl Carburettors are supplied with Strangler as Standard .31

"SOLEX" CARBURETTORS "M" TYPEHot air Muffs .No 1Diameterof Exhaust Pipe22 to 28 %No 2Diameterof Exhaust Pipe26 to 40%No 3Diameterof Exhaust Pipe38 to 48 %No 4Diameterof Exhaust Pipe46 to 58%Price . . . 6/- 8/- l0/- 12/-PRICE OF PARTS STANDARD ON ALL CARBURETTORS.Main Jet 2/-Auxiliary Jet 1/6Main Jet Main Jet Stand 4/6Stand Main Jet Stand Cap"MH"or"MV" 2/6 7/3Horizontal or Vertical . Jet Carrier Washer -/3Throttle Throttle abutment plate . 2/6abutment Slow running screw - / 11plate5 / _with Nut for above -/9Parts for Butterfly Screws Throttle stop screw -/ 10 8/6Spindle .Throttle Lever 1/3Nut for Throttle Spindle pair 2/-Washer for Above -/3Swivelling Petrol Swivelling Union Nut 2/6Union .Swivelling Union 2/6 5/3Washer for Union Nut -/3Nut and Bolt for Filter Union 2/ 6Union for Filter 4/ -Direct Filter . Gauze for Filter 1/3 8/3Large Washer for Filter -/3Small Washer for Filter -/3Nut and Bolt for Filter Union 2/ 6Union for Filter 4/ -Indirect Filter . Gauze for Filter 1/3 8/3Large washer for Filter -/3Small washer for Filter - / 3Needle and Seating with washer 5/-Washer for Needle seating -/3Fixing Screw for Air Bell -/6Choke Tube fixing screw -/6Tickler complete -/6Screw for collar -/9Roller with flat for Strangler attachment collar . -/10Screwed roller for Strangler attachment collar . -/10Union for suction pipe of Autovac 2/-Dashboard Strangler control 7/6Ball joint 2/6Copper Tube 6X8 for needle valve . per foot 1/6Cable for Strangler control per foot -/3Clip for cable 1/-Lever for Strangler horizontal or vertical 1/3Spring for Strangler 1/-Special Carburettor for Ford £ 5 .0 .0For spare part prices, see Ford Catalogue Type M.32

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