Part Two

Picture            
  Picture
  Series 40 DFA
   
          Picture
             
    Picture
    Picture
         
    Picture  
                   
            Picture
Picture    
        Picture
Picture
   

Weber Carburettor Adjustment Settings
        Adjustment Settings
       
                   
           

                 
  1)
Main Venturi
29   mm
By "adjustment settings" is meant a list of values assigned to the calibrated parts of a carburettor application on a given engine. If the carburettor is a multi-barrelled unit with synchronised opening of the throttles, each barrel will have the same adjustment settings; if throttle opening is of the differential type, then the settings are distinguished in two lists as primary and secondary.
   
  2)
Auxiliary Venturi
4.5   mm
   
  3)
Main fuel jet
1.10   mm
   
  4)
Main air bleed (corrector) jet
2.00   mm
   
  5)
Emulsion tube
F16
   
  6)
Idle speed fuel jet (fed from bowl)
0.50/F11 mm
   
  7)
Accelerating pump jet
0.35   mm
   
  8)
Accelerating pump drain jet
0.70   mm
   
  9)
Accelerating pump flow rate
 
Now, by considering a typical carburettor, say the 40 DCOE, it will be possible to explain the influence of the calibrated parts on engine operation and, with slight variations only, this information may be extended to the entire range of Weber carburettors.
 
    (per stroke, per barrel)
0.20   cc
 
  10)
Choke jet
0.60/F5 mm
 
  11-12) Needle valve (w/damper)
1.50   mm
 
  13)
Fuel level: distance between float top

                    and cover with gasket
8.5   mm
40 DCOE Carburettor
           
           
  14)
Weight of float
26   grams
Adjustment setting example
         
         
  15)
Flared air horn extensions
  none
This is a horizontal or sidedraft carburettor having twc identical barrels with synchronised throttles, fitted as a dual-unit application on a 4-cylinder, 1300 cc. engine providing 90 HP at 6000 rpm. It is a sports car power plant on which each carburettor barrel supplies fuel independently to one engine cylinder (single-feed system).
 
       
               
    To illustrate the DCOE Series carburettors, a section is shown in Fig. 29 and a colour chart on page 46. It is always possible to identify the main calibrated parts of a carburettor in-spite of the different systems adopted
                                 
      Picture    
                                 
FIG. 29
                             
Section through a DCOE Series carburettor
                     
1 Main Venturi - 2 Auxiliary Venturi - 3 Main fuel jet - 4 Main air jet - 5 Emulsion tube - 6 Idle speed fuel jet - 7 Accelerating pump jet - 11 Needle valve - 12 Valve needle - 14 Float - 16 Idle mixture adjusting screw - 17 Throttle valve.
 

when, for instance, the barrels are vertical. In the Weber carburettor designation, the first number indicates the barrel diameter in mm at throttle level and is followed by a group of code letters and, sometimes, by a second number completing the identification. Examples:
  consequence is, however, an increased resistance encountered by the flow through the carburettor. The sharper the passage section variations, the more evident are the effects of this resistance. The following relationship is thus used in calculations: - Main Venturi diameter = barrel diameter x 0.7 ... 0.9.
 
- 40 DCOE 32: horizontal (sidedraft) carburettor with two 40 mm barrels.
       
      The barrel diameter depends on engine and application specifications, and for this reason it will not be possible to give any detailed description here. However, as a preliminary selection criteria, it will prove useful to refer to the Weber Catalogue and Adjustment Setting Tables where also the other elements needed for a correct adjustment may be found. For an acceptable adjustment setting, any reduction in main Venturi diameter must be accompanied by a reduction in the diameter of the main (pilot) jet to prevent excessive mixture enrichment, as described later.
- 28/36 DLE 2: carburettor with two barrels, 28 mm primary and 36 mm secondary.
       
Parts are described below in the same order as given under the adjustment setting list on previous page. 1) Main or primary Venturi - Fig. 30
   
The main Venturi diameter - in this case, 29 mm
           
- is referred to the narrowest internal section (throat) and is selected from the results of tests run on the engine. The diameter chosen may be:
     
- greater, when maximum power at high rpm and maximum road speed are desired, or
         
- smaller, when better pick-up is desired with a penalty on maximum power.
  The main Venturi bears a number, stamped on its air cleaner side, showing its major striction size or smallest diameter. When the main Venturi is cast integral with the carburettor body this diameter is stamped on the outside face of the body casting, as
In fact, the task assigned to the main Venturi is to increase the vacuum acting on the carburettor main circuit in order to draw in and atomise the mixture; the
   
                     
  Picture    
                     
FIG. 30
                   
Main Venturis - In A, the main Venturi for a series DCOE carburettor having a 29 mm diameter. In B, section of a carburettor having an incorporated main Venturi with baffle for better mixture distribution and 25 mm diameter. In C, another carburettor section in which, in lieu of the baffle, a round bar serves the same purpose; the diameter is 24 mm.
 

is the case, for instance, of units 30 DIC and 26 IMB. Two graphs are provided for an approximate determination of main Venturi diameters: the first
     
Picture
(Fig. 31) covers current types of 2 to 6 cylinder engines fitting a single-barrel carburettor and the second (Fig. 32) covers sports engines designed on the singlefeed system, namely, one carburettor barrel to each
 
               
  Picture  
         
FIG. 31
          FIG. 32
   
Main Venturi diameter selection chart for 4-stroke, 1 to 6 cylinder engines having maximum output at around 5000 rpm. All engines fed by one single-barrel down- or side-draft carburettor, without supercharger. If the engine has 2 cylinders select a Venturi corresponding to twice the engine capacity. Examples: a 1-litre, 4-cylinder engine requires a 19-22 mm dia. Venturi; a 1-litre, 2-cylinder engine requires a 27-32 mm dia. Venturi.
    Main Venturi diameter selection chart for 4-stroke sports engines without supercharger and with feed by one down- or side-draft carburettor to every cylinder. The three curves plotted refer to maximum output speed rates of 6000, 8000 and 10,000 rpm. Example: a 4-cylinder, 1300 cc engine will have 325 cc unit capacity and will require Venturis of 29 mm dia. at 6000 rpm, 37 mm dia. at 8000 rpm and about 43 mm dia. at 10,000 rpm.
         

                 

                   
cylinder. In both graphs, engines operate on the fourstroke cycle and are not fitted with superchargers. 2) Auxiliary or secondary Venturi - Fig. 33 The value stamped in different locations refers to the narrowest section T of the spray nozzle through which
    the mixture flows and indicates that the cross-sectional area is the same as the one of a hole having the same diameter, say 4.5 mm as in A and B. The more commonly adopted diameters fall in the range between 3 and 5 mm, depending on different requirements: the
                     
        Picture  
                     
FIG. 33
               
Auxiliary Venturi - in A for DCOE series carburettors, in B for IDA series carburettors and in C for ICR series carburettors. T Spray nozzle tube minor section.

influence of the flow passage section is felt more markedly at high rpm rates. For special purposes, such as a desirable reduction in "mixture rejection" caused by engine "pulsating" induction, the elongated type of auxiliary Venturi is adopted on sports cars. In other cases, it proves beneficial - for improved mixture distribution - to give an asymmetric shape to the auxiliary Venturi portion nearest the throttle. For the smaller carburettors, a single diameter rating is factory-set and cannot be changed.
  Whenever the diameter of the main jet, or of any other jet, must be increased or decreased, it will be necessary to change the jet(s) with genuine Weber spare(s) and avoiding any use of pointed tools, etc.
 
             
 
Picture
           
Picture
 
             
  FIG. 35
       
  Graph for the selection of the main jet diameter as a function of main Venturi diameter, with 2.00 mm diameter as the datum figure for the air bleed jet.   ,
 
  Four-stroke, Otto-cycle engines.
     
  The main Venturi considered in the chart feeds 4 or 6 cylinders; if the cylinders fed are only 2, the jet diameter found must be multiplied by 0.90. In case it feeds just one cylinder (sports applications) the multiplication coefficient will be 0.75.
 
  Example: if a 29 mm dia. main Venturi feeds 4 or 6 cylinders it will require a main jet having a diameter of 1.45 to 1.75 mm; if it feeds only one cylinder the jet diameter will fall down to 1.10 or 1.30 mm. As these values are purely indicative, it is recommended to start the tests with the larger diameter jet, then reduce the size as needed.
           
FIG. 34
         
Main jets - in A the jet is fitted in a special holder, in B it is screwed in carburettor body casting, in C it is co-axial with the emulsion tube as in the DCOE series carburettors.
                 
      4) Air correction jet - Fig. 36
   
               
3) Main jet - Fig. 34
        The more commonly adopted diameters for this jet fall in the 1.50 to 2.30 mm range; by increasing the diameter of this jet, the mixture is weakened more at higher than lower engine rpm rates whereas by increasing the diameter of the main jet the mixture is enriched uniformly at both high and low engine rpm rates.
This is a calibrated component of great importance which is controlled with extreme care by measuring the flow rating of every single jet: the figure stamped on its side represents the nominal diameter in 1/100 of mm of the bore through which the fuel passes and must not be measured or cleaned with any pointed metal tool. The diameter - common values range between 0.80 and 1.80 mm - must be chosen according to the main Venturi, the air bleed jet, the number of cylinders to be fed, the grade of fuel used, etc. Useful though approximate data for a preliminary choice may be found in the graph of Fig. 35.
 
             
    Picture  
A recommended procedure for testing purposes is to start with the larger diameter jet, then reducing the diameter according to requirements.
       
On the basis of a correct adjustment setting, it may be said that every 1 mm increase in main Venturi diameter will call for an increase of about 0.05 mm in the main jet diameter.
     
             
  FIG. 36
       
  Air correction jet - For ICP series carburettors (A), for DCOE series carburettors (B) and for DCD series carburettors (C).

    The influence of the two jets thus used to best advantage in controlling adjustment setting and, for small variations, a 0.15 mm increase in the air correction jet diameter may be equivalent to an 0.05 mm reduction in the main jet diameter, considering tl
          three columns, one for each series of tubes used by Weber. Designations - for instance F11 - are not progressive but only indicative and there are also some performance differences between the tubes grouped in any of the blocks.
   
                 
    more common adjustment settings. 5) Emulsion tube
                Important note - Frequently, any change in emulsion tube must be accompanied by a variation in the diameter of the main jet or air correction jet.
     
    Its task is to emulsify the previously metered air issuir
             
    from the bleed jet with the fuel coming from the main jet. Its influence is more marked at small and average throttle opening angles and during accelerations (pick ups). Significant factors are:
       
                                     
            Calibrated parts -
                         
            The Weber part numbering system
           
           
                                     
    - Location and size of the orifices nearest the air bleed jet
            All types of parts in a carburettor are given a basic five figure number which relates to the "family" or group to which they belong. After the five figure number there follows a three digit number which identifies the particular part in question. Sizes are usually expressed in millimetres or fractions of a millimetre. For example, a fifty (point five mm) idle jet would be shown thus .050. A
   
    - Maximum outside diameter
                     
    - Location and size of orifices nearest the main jet. Some indicative information is provided below in tabulated form as an aid in selecting the right type of emulsion tube. Designation codes are subdivided in
           
                                                                   
       
 
Indicative table for emulsion tube selection
 
   
    Weber Part Numbers
 
 
61440...
 
  61450...
61455...
       
                                   
Picture
             
Picture
         
                 
Picture
  for:
            only for: DCOE-DCNF IDF-IDA (2V) DATRA-DFTA DMTR-DMTRA
        only for: DCD-DCZ carb. types
     
                    40-46 IDA (3V)
                   
                    40 IF (3V) and a lot of the remaining carb. types
                   
                                       
      Usual Application
                               
                                           
                                             
                                                       
                                                           
                                                                   
             
   
  F2-F3-F6-F7
  F2-F3-F4-F7
  F8-F13-F23
   
   
  F8-F9-F15
  F9-F11-F14
  F26-F30-F33
   
 
  Current Usage
  F16-F20-F21
  F15-F16
     
   
  F24-F26-F33
       
   
  F34-F35
       
 
  For mixture enrichment at low rpm or during slight
  accelerations (tubes without orifices at top)
  F3-F5-F7-F21
  F7
  F23-F30
   
 
  For mixture weakening at low rpm or during slight
  F20-F33-F34
  F2-F3-F11
  F8-F26-F33
   
 
  accelerations (tubes with orifices at top)
 
  F14-F15-F16
     
 
  Tubes with many orifices for high rpm mixture
  richness reductions when air bleed jet is larger
  than 2.00 mm
  F8-F16-F20

  F11-F19

  F8-F9-F31

   
 
  When mixture enrichment for slight accelerations
  is needed, the fuel reserve in emulsion well must
  be increased: this is obtained by fitting a tube
  having small outside diameter, orifices located
  prevailingly in the lower portion and a larger size
  air bleed jet to prevent excessive mixture richness
  at high rpm
  F3-F5-F25



  F7-F8



  F13



   
 
  Tubes for very large main fuel jets or for alcohol-
  F2-F20
  F2-F3-F4-F7
  F8-F10
   
 
  based fuels
  F24-F25
  F17
  F29
   
   
  F26
       

  135 (one point three five mm) would be shown .135 as the size exceeds one millimetre.
      For better choice, here below and on successive pages, there are drawings of all Weber emulsion tubes fitted on all range of carburettors.
 
                     
 
The basic numbers for calibrated parts are as follows:
      Drawing and relevant tables show the following measures:
     
                         
Picture     - Height
                 
    - External diameter
             
    - Diameter of the internal channel
         
    - Number and diameters of orifices.
       
    At the end of the drawings there is a conversion table where is possible to find all emulsion tubes "F" designation in progressive order.
   
                         
                                         
Emulsion tubes       part number 61440...
 
  Part
    Mm.
   
  Nr. holes
  x diameter
  (1/100
of mm.)
 
     
Number
 
  Type
  A
B
 
 
D
E
 
F
 
G
 
 
I
L
 
61440.120
  F3
4.5
3.5
4x125
2x100
  2x100
  4x100
         
61440.150
  F1
4.5
2.75
1x100
1x100
  2x140
  2x100
         
.151
 
  F26
4.5
2.75
WOO
2x100
  4x140
  4x100
         
.153
 
  F49
4.5
2.75
1x100
WOO
  2x140
  2x100
  2x100
2x100
 
     
.154
 
  F58
4.5
2.75
2x100
2x100
  2x140
  2x100
  2x100
2x100
 
     
61440.155
  F63
4.5
2.75
1x100
1x100
  2x150
  2x150
  2x125
       
61440.166
  F2
4.5
2.75
4x100
4x100
  4x140
  4x100
         
61440.181
  F3
4.5
2.75
4x100
4x100
  4x140
  4x100
         
.182
 
  F5
4.25
2.75
4x100
4x100
  4x140
  4x100
         
61440.196
  F4
4.75
2.75
4x100
4x100
  4x140
  4x100
         
.197
 
  F70
  5
2.75
4x100
4x100
 
-
 
  4x120
4x120
 
     
   
                                         
Picture  

Emulsion tubes   Part number 61440...
 
  Part
    mm.
   
  Nr. holes
  x diameter
  (1/100
of mm.)
   
Number
61440.211
  Type
  F6
A
4.25
B
2.75
C
2x100
D
4x100
E
 
  4x140
F
 
  4x100
  G
H
 
I
  L
.212
 
  F8
  5
3
 
2x125
4x125
  4x140
  4x100
       
.213
 
  F24
  4
2.75
2x100
4x100
  4x140
  4x100
       
.217
 
  F53
4.5
2.75
2x100
4x100
  4x140
  4x115
       
.218
 
  F56
4.5
2.75
2x100
4x100
  4x140
  4x150
       
.219
 
  F57
4.5
2.75
2x100
4x100
  4x140
  4x130
       
.223
 
  F80
  4
2.75
2x100
4x100
  4x140
  4x150
       
61440.216
  F50
4.5
2.75
-
4x140
  4x140
  4x140
  4x140
     
.224
 
  F81
4.5
2.75
4x140
4x140
  4x140
  4x140
  4x140
     
61440.220
  F66
4.5
2.75
4x160
4x120
  4x120
-
 
       
.222
 
  F78
4.5
2.75
4x160
2x120
  2x120
  2x120
       
61440.226
  F7
4.5
2.75
4x100
4x140
  4x100
         
61440.229
  F87
4.5
2.75
2x100
4x100
  4x140
  4x150
  4x150
     
61440.241
  F9
4.5
3.5
2x100
2x100
  2x100
  2x115
       
.246
 
  F51
4.5
3.5
2x100
2x100
  2x100
  2x115
  4x100
     
.249
 
  F75
4.5
3.5
2x100
2x100
  2x100
  4x115
       
61440.242
  F40
4.5
3.5
2x100
2x100
  2x100
  2x115
       
                         
  Picture  

Emulsion tubes   Part number 61440...
 
  Part
         
  Nr. holes
  x diameter
  (1/100
of mm.)
 
     
Number
61440.243
Type
F42
A
4.5
B
3.5
C
2x100
D
2x100
E
 
  2x100
  F
  2x115
G
 
H
 
1x50
 
I
L
 
.224
 
F47
4.5
3.5
2x100
2x100
  2x100
  2x115
 
2x100
 
     
.245
 
F48
4.5
3.5
2x100
2x100
  2x100
  2x115
  4x75
2x100
 
     
61440.247
F54
4.5
3.5
4x110
4x110
  4x110
  4x120
         
61440.261
F10
4.75
3.5
2x100
2x100
  2x100
  2x115
         
61440.281
F11
4.5
3.5
2x100
2x100
  2x100
  4x125
         
61440.301
F14
  5
  3
2x115
4x115
  2x115
           
.302
 
F43
  5
  3
2x115
4x140
  2x115
  2x120
         
.303
 
F73
  5
  3
2x115
4x140
  4x140
  4x140
         
.304
 
F74
  5
  3
2x115
4x140
  2x115
  2x120
  2x100
       
.305
 
F84
  4
  3
2x115
4x140
  4x140
  4x140
         
61440.321
F15
4.75
3.50
 
2x115
  2x115
  4x115
  4x115
-
 
     
.328
 
F68
4.75
3.50
2x100
2x115
 
  4x115
  4x115
4x150
 
     
61440.323
F52
4.65
3.50
2x115
2x115
  4x115
  2x75
         
                             
 
Picture
   

Emulsion tubes   Part number 61440...
 
  Part
    mm.
   
  Nr. holes
  x diameter
  (1/100
of mm.)
 
   
Number
 
Type
A
 
B
 
C
D
  E
 
G
 
  H
I
L
61440.325
F60
4.1
2.50
-
2x115
  2x115
  4x115
  4x115
     
.326
 
F61
4.1
2.50
-
2x115
  2x115
  4x115
-
 
     
.329
 
F82
4.1
2.50
4x100
2x115
  2x115
  4x115
  4x115
     
61440.341
F16
4.75
3.25
4x115
4x115
  4x115
-
 
       
.343
 
F71
4.75
3.25
4x115
4x115
  4x115
  4x115
       
.344
 
F85
4.75
3.25
4x140
4x115
  4x115
  4x115
       
61440.351
F17
4.5
3.25
2x115
2x115
  2x115
         
.352
 
F38
4.5
3.25
2x115
2x115
  2x115
  1x125
       
61440.356
F18
4.65
3.5
2x115
2x115
  2x115
  4x115
  4x115
  -
   
.357
 
F67
4.65
3.5
2x115
2x115
  2x115
  4x115
  4x115
4x150
 
   
61440.359
F86
4.65
3.5
4x115
2x115
  2x115
  1x115
  4x140
     
61440.365
F20
4.5
3
 
4x115
4x115
  4x145
  4x145
       
61440.371
F21
4.5
2.75
4x100
4x140
  4x100
  2x100
       
.372
 
F23
4.5
2.75
4x100
4x140
  4x100
  2x100
  2x100
     
 
                             
  Picture    
                             
      Picture      

Emulsion tubes   Part number 61440...
Part
Number
 
  Type
  mm.
   
  Nr. holes x diameter
  (1/100
of mm.)
 
   
  A
B
 
C
D
E
 
F
 
H
 
I
L
61440.452
.471
  F3
  F2
4.5
4.5
2.75
2.75
2x100
2x100
4x100
4x100
  4x140
  4x140
4x100
4x100
  2x120
  -
     
61440.454
  F77
4.7
3.7
4x130
4x100
  4x100
4x100
  4x100
4x130
 
4x150
2x100
61440.488
  F25
  4
2.75
4x140
4x140
  2x100
         
61440.501
  F29
4.5
3.5
4x100
4x100
           
61440.502
  F33
4.5
3.5
4x120
4x120
           
61440.515
  F30
4.5
3.5
2x100
2x100
  2x100
2x115
  1x120
     
61440.525
.526
  F34
  F35
4.5
4.5
2.75
2.75
2x100
2x100
2x100
  2x100
  2x100
2x100
       
                               
  Picture  
                               
      Picture        

Emulsion tubes   Part number 61450...
 
  Part
Number
 
  Type
mm.
   
  Nr. holes
  x diameter
  (1/100
of mm.)
 
   
  A
  B
C
 
D
 
E
 
 
G
 
H
 
  I
L
61450.026
  F1
7.5
  3
  2x100
-
 
  8x100
-
 
  4x250
     
.027
 
  F2
7.5
  3
  2x100
2x100
  8x100
-
 
  4x250
     
.028
 
  F3
7.5
  3
  2x100
2x100
  8x100
  4x100
  4x250
     
.029
 
  F5
7.5
  3
-
 
2x100
  8x100
  4x100
  4x250
     
.030
 
  F9
8.2
  3
  2x100
2x100
  8x100
 
  4x250
     
.031
 
  F11
  8
  3
  2x100
2x100
  8x100
  4x100
  4x250
     
.032
 
  F15
  8
  3
  2x100
2x100
  Sx100
-
 
  4x250
     
61450.036
  F50
8.1
  3
  4x110
4x110
  4x100
  4x100
  4x80
4x200
 
   
61450.051
  F4
7.5
  3
  2x100
2x100
  8x100
  4x100
  4x100
4x100
 
4x250
 
.052
 
  F17
6.5
  3
  2x100
2x100
  8x100
  4x100
  4x100
4x100
 
4x250
 
.053
 
  F20
7.5
  3
  2x100
2x100
  8x100
  4x100
  4x100
-
 
4x250
 
.054
 
  F34
7.5
  4
  2x100
2x100
  8x100
  4x100
  4x100
4x100
 
4x250
 
61450.057
  F41
8.1
  3
  2x80
4x250
  4x100
  4x100
  4x80
4x200
 
   
.058
 
  F47
  8
  3
  2x80
4x250
  4x100
  4x100
  4x80
4x200
 
   
61450.071
  F6
8.3
  3
  4x100
4x100
  4x100
  4x100
  4x100
4x250
 
   
61450.091
  F7
7.5
  3
 
8x100
  4x100
  4x250
       
.092
 
  F8
7.5
  3
  2x100
8x100
  4x100
  4x250
       
61450.111
  F10
7.5
 
  4x100
8x100
  4x250
         
 
 
Picture
 
                               
      Picture      

Emulsion tubes   Part number 61450...
 
Part
Number
61450.131
Type
F12
  mm.
   
  Nr. holes
  x diameter
  (1/100
of mm.)
 
   

7.5

5
 

8x100
 
4x250
           
61450.166
F14
8.2
3
 
8x100
  4x250
           
61450.167
F49
8.2
3
 
2x125
  2x80
  2x80
  4x90
  4x90
4x250
 
   
61450.181
F16
8.2
3
 
8x100
  4x250
           
61450.210
F19
8.2
3.5
8x100
  4x100
  4x100
  4x100
  4x250
     
61450.221
F21
5.7
3.5
4x120
  4x120
  4x200
         
.222
 
F22
  6
3.5
4x120
  4x120
  4x200
         
61450.224
F24
  5
3
 
4x150
 
  4x150
-
 
  4x200
     
.226
 
F26
  5
3
 
4x150
  -
  4x150
 
  4x200
     
.234
 
F38
  5
3
 
2x150
  2x150
  4x150
  4x150
  4x200
     
                               
 
Picture
 
                               
    Picture        

 
Emulsion tubes   Part number 61450...
 
  Part
    Mm.
   
  Nr. holes
  x diameter
  (1/100
of mm.)
 
   
 
Number
 
Type
 
 
B
 
C
D
E
 
  F
 
  H
I
L
  61450.225
F25
 
  6
3.5
4x120
4x120
-
 
  4x200
       
 
  .228
F28
 
  6
3.5
4x120
4x120
  4x120
  4x200
       
  61450.227
F27
 
6.2
3.5
4x115
4x115
  4x115
  2x115
-
 
4x150
 
   
 
  .229
F30
 
6.2
3.5
4x140
4x140
  4x115
  2x115
  2x115
4x150
 
   
 
  .232
F36
 
5.9
3.5
-
2x140
  2x115
  2x115
-
 
4x150
 
   
 
  .238
F44
 
5.5
3.5
4x140
4x140
  4x115
  2x115
  2x115
4x150
 
   
 
  .241
F46
 
3.5
3.5
-
2x140
  2x115
  2x115
 
4x150
 
   
  61450.230
F32
 
  7
3
 
8x100
4x100
  4x100
  4x250
       
  61450.231
F33
 
  5
3
 
2x100
2x100
  4x120
  4x150
  4x200
     
  61450.235
F39
 
  5
3
 
1x150
4x150
  4x150
  4x150
  4x200
     
  61450.236
F42
 
6.2
3.5
4x200
4x200
  4x160
  4x140
  4x150
4x150
 
4x180
 
  61450.237
F43
 
6.2
3.5
4x180
4x200
  4x120
  4x140
  4x115
2x115
 
4x150
 
                               
    Picture  
                               
      Picture      

Emulsion tubes   Part number 61450...
Part
    mm.
  Nr. holes x diameter
(1/100 of mm.)
 
 
Number
  Type
           
61450.239
  F30
  spec.
  6.2
3.5
4x140
  4x140   2x115   2x115
2x115   4x1500
 
 
61450.240
  F45
  5.3
3.5
4x120
  4x120   4x200
   
61450.242
  F46
  spec.
  6
3.5
2x140
  2x115   2x115   4x150
   
       
Part number 61455...
 
61455.001
  F4
5.25
2.5
 
  4x100
-
4x100
4x125
     
.002
 
  F5
6.25
2.5
 
  4x100
4x125
4x100
4x125
     
.003
 
  F6
5.25
2.5
4x125
  4x100
-
4x100
4x125
     
.005
 
  F8
5.25
2.5
4x125
  4x100
4x125
4x100
4x125
     
.006
 
  F9
6.25
2.5
4x125
  4x100
4x125
4x100
4x125
     
.007
 
  F10
  4
2.5
-
  4x95
4x125
4x95
4x125
     
.008
 
  F11
  4
2.5
 
  4x95
4x125
-
       
61455.031
  F7
5.5
  3
4x100
  4x100
4x100
4x100
4x100
     
61455.046
  F13
5.5
3.5
4x125
  4x125
4x125
4x125
       
61455.061
  F14
  6
3.5
4x100
  4x100
4x100
2x100
       
.062
 
  F18
5.5
3.5
4x125
  4x125
4x100
2x100
       
     
  Picture    
      Picture          

Emulsion tubes   Part number 61455...
 
  Part
    mm.
   
  Nr. holes
  x diameter
  (1/100
of mm.)
 
   
Number
61455.091
Type
F17
  A
  6
B
3.5
C
4x140
D
4x100
E
 
  4x100
F
 
  2x100
  G

  H

I

L

61455.106
F19
  6
3.5
4x200
4x100
           
61455.121
F20
  6
3.5
4x100
4x100
  4x100
         
61455.136
F22
  6
3.5
 
4x125
  4x125
  4x125
  4x125
4x125
 
   
.137
 
F25
  6
3.5
4x100
4x115
-
 
-
 
  -
  -
   
.138
 
F26
5.75
3.5
-
4x125
  4x125
  4x125
  4x125
4x125
 
   
.139
 
F33
5.75
3.5
 
4x125
  4x125
  4x125
 
  -
   
61455.151
F23
5.5
3.5
2x115
2x100
  2x100
  2x100
       
.152
 
F30
5.5
3.5
4x115
4x100
  4x100
  4x100
       
61455.181
F27
5.5
3.5
2x125
2x125
  4x125
  4x125
       
61455.196
F28
  6
3.5
4x150
             
         
                           
  Picture  
                           
    Picture      

Emulsion tubes   Part number 61455...
 
Part
Number
 
  Type
  mm.
   
  Nr. holes
  x diameter
  (1/100
of mm.)
 
   
  A
B
 
C
  D
  E
  F
G
 
H
 
 
L
61455.211
  F29
  5
3.5
4x100
  4x100
  4x100
  2x100
       
61455.231
  F31
5.5
3.5
4x125
  4x125
  4x125
  4x125
  4x125
4x125
 
   
61455.351
  F1
4.5
2.5
4x100
  4x140
  4x100
  4x100
       
.352
 
  F2
4.75
2.5
4x100
  -
  4x100
  4x100
       
.353
 
  F3
  4
2.5
4x100
  4x140
  4x100
  4x100
       
61455.366
  F16
5.35
2.5
4x100
  4x100
  4x100
  4x100
       
61455.421
  F1
4.5
2.5
4x100
  4x140
  4x140
  4x100
       
                             
  Picture    
                             
        Picture        

  Conversion table for `E' tubes
   
  `F'
Designation
  Fl
Part
 
  Number
  61440.150
  `F'
  Designation
  F66
  Part
Number
 
61440.220
 
  `F'
  Designation
  F34
Part
 
  Number
  61450.054
  F2
  .166/471
  F67
.357
 
  F36
  .232
  F3
  .120/181/452
  F68
.328
 
  F38
  .234
  F4
  .196
  F70
.197
 
  F39
  .235
  F5
  .182
  F71
.343
 
  F41
  .057
  F6
  .211
  F73
.303
 
  F42
  .236
  F7
  .226
  F74
.304
 
  F43
  .237
  F8
  .212
  F77
.454
 
  F44
  .238
  F9
  .241
  F78
.222
 
  F45
  .240
  F10
  .261
  F80
.223
 
  F46
  .241
  F11
  .281
  F81
.224
 
  F46 (special)
  .242
  F14
  .301
  F82
.329
 
  F47
  .058
  F15
  .321
  F84
.305
 
  F49
  .167
  F16
  .341
  F85
.344
 
  F50
  .036
  F17
  .351
  F86
.359
 
  Fl
  61455.351/421
  F18
  .356
  F87
.229
 
  F2
  .352
  F20
  .365
  Fl
61450.026
 
  F3
  .353
  F21
  .371
  F2
.027
 
  F4
  .001
  F23
  .372
  F3
.028
 
  F5
  .002
  F24
  .213
  F4
.051
 
  F6
  .003
  F25
  .488
  F5
.029
 
  F7
  .031
  F26
  .151
  F6
.071
 
  F8
  .005
  F29
  .501
  F7
.091
 
  F9
  .006
  F30
  .515
  F8
.092
 
  F10
  .007
  F33
  .502
  F9
.030
 
  F11
  .008
  F34
  .525
  F10
.111
 
  F13
  .046
  F35
  .526
  F11
.031
 
  F14
  .061
  F36
  .352
  F12
.131
 
  F16
  .366
  F40
  .242
  F14
.166
 
  F17
  .091
  F42
  .243
  F15
.032
 
  F18
  .062
  F43
  .302
  F16
.181
 
  F19
  .106
  F47
  .244
  F17
.052
 
  F20
  .121
  F48
  .245
  F19
.210
 
  F22
  .136
  F49
  .153
  F20
.054
 
  F23
  .151
  F50
  .216
  F21
.221
 
  F25
  .137
  F51
  .246
  F22
.222
 
  F26
  .138
  F52
  .323
  F24
.224
 
  F27
  .181
  F53
  .217
  F25
.225
 
  F28
  .196
  F54
  .247
  F26
.226
 
  F29
  .211
  F56
  .218
  F27
.227
 
  F30
  .152
  F57
  .219
  F28
.228
 
  F31
  .231
  F58
  .154
  F30
.229
 
  F33
  .139
  F60
  .325
  F30 (special)
.239
 
   
  F61
  .326
  F32
.230
 
   
  F63
  .155
  F33
.231
 
   
     

  Carb Type
  Basic Part Number
  Sizes available (in mm.)
  Auxiliary Venturis
   
  28/36 DCD
  36 DCD
  69001
  3.00, 3.50, 4.50
  30 DGF, DGS
  71119
  3.50, 4.00, 4.50
  30/32 DMTE
70749
  3.50 5.00
  32 ADF
70512
  3.00, 3.50
  32 DARA
  32 DIVISA
  32/36 DHSA
71113
  3.50, 4.00
  32, 32/34 and 34 DAT, DATRA, DFT, DFTA, DFTH, DFTM,
  DIVISA, DMTC, DMTL, DMTR, DMTRA, DMTT, DRTC,
  DRTM, DSTA
71115
  4.00, 4.50
  32 DFM, DIR
  32/36 DFAV
71110
3.50
  32 DRT
71127
  3.50 4.00 4 50
  32 DSTA, DRTC, DRTM
71138
4.00
  32 IBF, IBP
71132
4.50
  32 TL
70751
 
  32 TLA
31956016
 
  32 TLDR
70130
 
  32 & 34 TLC, TLF, TLM, TLP
70745
  3.50, 4.00 4 50
  32/34 TLDA, TILDE, TLDM
70126
3.00
  32/36 DGV or DGAV
71111
3.50
  40 DCOE

699 2
70001
70003
70005
3.50, 4.50 With air horns
3.50, 4.50 Without air horns
3.50, 4.50 With air horns
4.50 Extended type with air horns
  40 DCOM
69909
6.00
  40 DCN
  Excluding 40 DCN 21
71102
  3.50, 4.00, 4.50
  40 DCN 21
70504
4.50
  40 DCNF
71107
  3.50 4.50
  40mm 3 Barrel
  Carburettors
71103
  3.50 4.50
  40 I DF 13,15, 70
69002
  4.00 4.50
  40 OF (late)
71102
3.00
  42 DCNF, 44 DCNF
70503
  3.50, 4.00, 4.50
  42 DCOE
70002
  3.50 4.50 With air horns
  44 IDF
71102
  3.50, 4 00, 4.50
  45 DCOE
69602
69904
3.50, 4.00, 4.50, 5.00 With air horns
4.50 Without air horns
  46mm 3 Barrel Carburettors
71104
  4.50 5.00
  48 DCOE
68819
  4.50, 5.00 With air horns
  48 DCO/SP
68820
  5.00, 6.50 7.00
  48 IDA
69009
  3 50 4.00 4.50 5.00
  48 OF
71124
  3.00, 3.50, 4.00, 4.50 5.00
  50 DCO/SP
68820
  5.00, 6.50, 7.00
  55 DCO/SP
68820
  5.00, 6.50, 7.00
  Chokes (Main Venturis)
   
  28/36 DCD
  (Primary Barrel)
71702
  18, 19, 20, 21, 22, 23, 24, 25, 26
  28/36 DCD (Secondary Barrel)
  36 DCD
71701
  19, 20, 21, 22, 23, 24, 25, 26, 27, 28
  40 DCN, 40 DCNF
72129
  24, 25, 26, 28, 29 30, 31, 32, 33, 34, 35 36
  40 DCOE
72303, 72302 (Air By-Pass)
  24 25 26, 27, 28, 29, 30, 31, 32, 33, 34,
  35,36
  40 IDA 3 Barrel
  40 IDT 3 Barrel
  40 IDTP 3 Barrel
71502
  30, 32, 34
  40 IDL 3 Barrel
  40 IDS 3 Barrel
71505
  7,32
  40 OF 13, 15, 19
71506
  27, 28, 30, 32
  42 DCNF
72106
  32, 34, 36
  42 DCOE
72304
  24, 25, 26, 27, 29, 30, 31, 32, 33, 34
     

  Carb Type
Basic Part Number
  Sizes available (in mm.)
     
  Chokes (Main Venturis)
           
  44 DCNF
  44 OF
72108
 
71507
 
  34, 36, 37, 38
  32, 34, 36
       
  45 DCOE
  46 IDA 3 Barrel
  48 DCOE
  48 & 50 DCO/SP
72110, 72116 i,/ir By-Pass)
71504
72117
 
72136
 
  28,30,32,33,34,35,36,37,38.39, 40
  40,42
 
  40, 41, 42
  42, 43, 46
  48 IDA
72128
 
  36: 37,38,39:40,41,42,43,44:45
 
  48 IDF
  55 DCOISP
  Main Jets
  DCO, DCOE, DCNL, DCOM, DCOISP, OF and 48 IDA


71513
 
72135
 

73401


  40:41
  46t47,48
 
0.80, 0.85,0.90,0.95,1.00,1.05.1.07, 1.10,
 
  112,1.15,1.17; 1.20, 1.22, 1.25, 1.30, 1.32,
  1.35,1.40,1.42. 1.45, 1.50, 1.55, 1.60, 1.65,
  1.70, 1.75, 1.80. 1.85, 1.90, 1.95, 2.00, 2.05,
  2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45,
  2.50, 2.60: 2.90
  DAT, DATR, DATRA, DCA, DCNF, DCNFA, DCNVH, DCNV,
  DFT DFTA, DFTH, DFTM, DMTC, DMTE DMTL, DMTR.
  DMTRA, DMTT, DIRT DRTC, DRTM, DSTA
  ADC, ADF, ADFA, ADHA, ADL, ADLA, A151-D, ADS, ADSD,
  DAC, DAR, DARA, DATA, DCB. DCD, DCHE, DCOF, DCN,
  DCZ, DFA, DFAV, DFC, DFE. DFM, DFI, DFV, DGAR,
  DGAS, DGAV, DGF, DGMS, DGS; DGV: DHS, DHSA,
  DHTA, DIC: DICA, DIR. DM, DMA, DMS, DIVISA, DIPS, IBA,
  IBF, IBP, IBSA, IBSH, ICB, ICEV, ICF, ICH: ICP, ICR. IDAP,
  IDT, IMB, IMPE, TL, TLA, TLC, TLDA, TILDE, TLDM, TLDR,
  TLF, TLM, TLP and 3 Barrel Carburettors
  Idle Jets
  28/36 DCB-DCD, DCHE, ICF: ICP, IMB, IMPE. 36 DCD,
  40 DCN, DCZ
  ADC, ADF, ADFA, ADL, ADLA, ADLD, DAC, DAR. DARA,
  DAT, DATA, DATR, DATRA, DCOF, DFAV, DFC, DFE, DFM,
  DFT, DFTA: DFTH, DFTM, DFV, DGAR, DGAS, DGAV. DGF,
  DGMS, DGS, DGV, DHS, DHSA, DHTA, DIC, DICA, DMS,
  DIVISA, DMTC, DMTE. DMTL, DMTR, DMTRA, DMTT, DPS,
  DRT, DRTC, DRTM, DSTA, IBA, ICB, ICEV, ICR, IDAP, IDT,
  TL , TLA, TLC, TLF, 3 Barrel Carburettors
  TLDR
  28/36 DM-DMA, DCA
  DCNF, DCNFA, DCNV, DCNVH, OF
  ADF, ADS, DIR
  ADF, ADSD, DIR, DMS
  ADFA. ADL, ADLA, ADHA, DARA, DGF DGAR, DGS, DIR,
  DPS, IBF, IBSA, IBSH, IBP, ICH
73405
 

I
73801




74401
74403
 



74704
 
74405
 
74407
 
74408
 
74409
 
  0.90,0.9510.97,1.00,1.02,1.05,1.07, 1.10,
 
  1.12, 1.15, 1.17,1.20:1.25,1.27,1.30,1.35,
  1.40,1.45,1.50,11.55: 1.60, 1.65,
  1.80,1.85,1.90,11.95, 2.00
  0.40, 0.45, 0.50, 0.60, 0.65, 0.70,
  0.82, 0.85, 0.87, 0.90, 0.95, 0.97,
1.70, 1.75,
0.75, 0.80,
1.00, 1.02,
  1.03; 1.05, 1.07.1.10,112,11.115,11.17,120:
  1.22: 1.25,1.27,11.30,1.32,1.35:
  11.42,1.45,1.47,11.50,1.52,1.55.
  11.62,1.65,11.70,11.75,1.80,1.85,
  2.00, 2.05, 2.10, 2.15, 2.20, 2.30
 
0.40, 0.45, 0.47. 0.50, 0.55, 0.60,
  0.75,0.80,0.90,0.95. 1.00, 1.20,
  0.00, 0.40: 0.42, 0.45, 0.47, 0.50,
  0.57, 0.60: 0.65, 0.70. 0.75, 0.80:
  0.95, 1.00
 

50
  0.40, 0.42, 0.45, 0.47, 0.50, 0.52,
  0.60. 0.65, 0.70
  0.40.0.45, 0.50, 0.55
  0.45, 0.47, 0.50, 0.55
  0.40, 0.42 0.45, 0.47, 0.50, 0.52,
  0.60
11.3711.40:
1.5711.60,
1.90. 1.95,


0.65, 0.70,
1.25
0.52, 0.55,
0.85, 0.90,



0.55, 0.57:

0.55, 0.57,
  48 IDA (idle jet)
  48 IDA (idle jet holder)
74823
 
77903
 
  0.40,0.45,0.50,0.55,0.6Q 0.65,0.70,0.75,0.80
  0.60, 1.00. 1.10, 1.20, 1.25, 1.50
 
         
                         
   
Idle Jets for DCOE series carburettors
                   
            Picture  
  Picture    

                   
Basic Part
  Type
 
  A
B
  C
       
  T
 
Number
   
0
(mm.)
 
H(mm.)
Nr.
holes
0
(mm.)
 
    Sizes available (in mm.)
 
74814. ...
  F1
  1.40
    2
  1.40
0.00,
0.30,
0.35,
0.40,
0.45,
0.50,
0.52,
0.55,
74815....
  F2
  1.50
    1
  1.40
0.60,
0.65,
0.70,
0.75,
0.80,
0.85,
0.90,
0.95,
74816....
  F3
  1.40
    2
  1.60
1.00,
1.10,
1.20,
1.30,
1.35,
1.40,
1.50,
1.60,
74817. ...
  F4
  2.00
    1
  1.40
1.70
             
74818....
  F5
  1.40
    1
  1.60
               
74819....
  F6
  2.00
    1
  0.70
               
74820....
  F7
  2.00
    2
  1.20
               
74821....
  F8
  2.00
    1
  1.20
               
74822....
  F9
  2.00
    1
  1.00
               
74824....
  F11
  1.50
    1
  1.20
               
74825....
  F12
  1.50
    1
  0.90
               
74826....
  F13
  2.00
    2
  0.90
               
74827....
  F14
  1.70
    1
  1.20
               
74828....
  F15
  2.00
    2
  1.05
               
74829....
  F16
  2.10
    2
  1.30
               
74830. ...
F17
  2.10
2
1.35
                   
74831....
F18
  2.10
2
1.60
                   
74832....
F19
  2.00
1
1.20
                   
74833....
F21
  2.10
4
1.10
                   
74834....
F22
  2.10
4
1.20
                   
74835....
F23
  2.00
1
1.25
                   
74836....
F24
  2.00
1
1.55
                   
74837....
F25
  2.00
1
1.50
                   
74838....
F26
  2.00
2
1.25
                   
74839....
F27
  2.00
1
1.60
                   
                     
                                                       
  6) Idle jet - Figs 37 and 38
                  carburettor with idle jet of the type incorporating the idle air jet: in the second, this air jet is separate. The idle jet belonging to the adjustment setting being considered here, has a diameter of 0.50 mm and designation 50 F11. Following is a tabulation showing - next to every F designation - the respective and equivalent air jet diameter.
 
  Two widely used arrangements are illustrated in Figs. 37 and 38: the first shows a DCOE series
           
                             
  Picture          
                                     
       
Picture
                                                       
  FIG. 37
                                                   
  Idle jet - Shown here is the idle speed circuit and fuel jet for the DCOE series carburettors, with air jet (dimensions B) incorporated in fuel jet (dimension A).
      FIG. 38
                     
        Idle jet - As shown here, this jet is separate from the idle air jet Gam; dimension B is not a calibrated value. This is an example of idle speed system fed from emulsion tube well.
 
  This is an example of idle speed system fed from float chamber.
         

   
  Carb Type
Acceleration Pump Jets
  Basic Part Number
  Sizes available (in mm.)
   
  40 IDA 3 Barrel
  40 IDL 3 Barrel
  46 IDA 3 Barrel
  76201

  0.40, 0.45, 0.50, 0.60

   
  40 IDT 3 Barrel
  40 IDTP 3 Barrel
  40 IF3C 3 Barrel
  76202

  0.40, 0.50

   
  28/36 DCD, 36 DCD
  76203
  0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.80
  Pump operates on primary Barrel only
   
  OF Series
  76210
  0.35, 0.40, 0.50, 0.55
   
  32/36 DFAV, 32 DFM, DIR, DFE, DFD, DHSA, DIVISA,
  ADSD, ADSA
  76211
  0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70
   
  40 DFAV, DFI, DGAS
  76212
  0.40, 0.45, 0.50, 0.55, 0.60, 0.70
   
  40 DCN or DCNF Series
  76215
  0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70
   
  32/36 DGAV & DGV
  76226
0.50 (for alternative sizes use 76212 with
secondary barrel pump orifice blocked)
   
  DSTA
  76224
0.60
   
  32 DIR, DAR, DARA
  76227
  0.50, 0.60
   
  48 IDA
  76402
  0.35, 0.50, 0.60, 0.70
   
  ADF, ADFA, DAT, DATR, DATRA, DFT, DFTA, DFTM, DGF,
  DGS, 32/34 DMTC, DMTE, DMTL, DMTR, DMTRA, DMTT,
  DRT, ICH
  76407

  0.40, 0.45, 0.50, 0.55

   
  DMTC
  76410
  0.40, 0.45, 0.50, 0.55, 0.60
   
  IBF, IBP
  76413
  0.45, 0.50, 0.55, 0.60
   
  DFT
  76417
  0.45, 0.50
   
  DRTC
  76420
  0.50, 0.55
   
  DRTM
  76422
  0.40, 0.50, 0.55
   
  28/32 TLDM, TLM
  76426
  0.40, 0.45
   
  TLA
  76432
0.35
   
  TL
  76435
0.35
   
  TLDR
  76439
  0.40, 0.50, 0.55
   
  DFTH
  76443
  0.45, 0.50
   
  TLC, TLP
  76444
  0.40, 0.50
   
  TLDE
  76451
0.40
   
  26/28 TLDM
  76453
0.40
   
  TLDA
  76454
0.45
   
  TLF
  76458
0.35
   
  DCO, DCOE, DCO/SP
  76801
  0.30, 0.35 0.40, 0.45, 0.50, 0.55, 0.60, 0.65,
  0.70, 0.75, 0.80, 0.85, 0.90
   
  DCOM
  76818
  0.35, 0.40, 0.45
   
  Pump Bleed
  79701
  0.00, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65,
  0.70, 0.75, 0.80, 0.85, 0.90, 1.00, 1.50
   
  Air Correction Jets
   
   
  ADC, ADF, ADFA, ADHA, ADL, ADS, ADSD, DAC, DAR,
  DARA, DCN, DCOF, DFAV, DFC, DFE, DFD, DFI, DFM,
  DGAV, DGF, DGS, DGV, DHSA, DIC, DICA, DIR, DMSA,
  IBA, IBP, ICF, IBSA, IMB, OC, TLDA, TLDE, TLDM and
  3 Barrel Carburettors
  77201


  1.00, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40,
  1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80,
  1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20,
  2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.55, 2.60,
  2.65, 2.70, 2.80
   
  DCNL, DCO, DCOE, DCOM, DCO/SP, IDA, OF


  77401


  0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15,
  1.20, 1.25, 1.30, 1.35, 1.40,1.48,1.50, 1.55,
  1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95,
  2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35,
  2.40, 2.50
   
  DCNF, DMTRA, DATRA, DFTA, DMTR

  77501

  1.00, 1.20, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55,
  1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95,
  2.00, 2.05, 2.10, 2.15, 2.20, 2.30, 2.40, 2.50
   
  28/36-36 DCD, DCZ - 28/36 DCB, DCHE


  77502


  1.00, 1.05, 1.15, 1.20, 1.25, 1.30, 1.40, 1.45,
  1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85,
  1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25,
  2.30, 2.35, 2.40, 2.45, 2.50, 2.55, 2.60, 2.65,
  2.70, 2.75, 2.80, 2.85, 2.90, 2.95, 3.00
         
40
       

  Carb Type
  Basic Part Number
Sizes available (in mm.)
     
  Needle Valves
                 
  DCOE (Solid Type)
  79401
1.50,
1.75,
2.00,
2.25,
2.50,
3.00
   
  DCO
  79502
1.75
             
  DCN, DCOE, DCOM, DCO/SP (Spring Loaded)
  79503
1.50,
1.75,
2.00,
2.25,
2.50,
3.00
   
  46 and 48 IDA 2 Barrel
  79504
1.75,
2.00,
2.50,
3.00
       
  DHSA, DCD, DIC, DICA, ICA, ICF, DARA, DATRA, DMTL,
  DMTR, DMTRA, DFD, DFM, DIVISA, DATR, DCOF, DHTA,
  DFC, DATC, DMTC, DCOE, DGF, DGS, IBA, IBSA, IBSH,
  IBP, ICB, ICR, ICEV, ICE, ICF, ICH, ICP, ICT, OF
  79507

1.50,

1.75,

2.00,

2.25

       
  40 & 46 mm
  3 Barrel Carburettors
  79508
1.75,
2.00
           
  ADFA, DIR, DFM
  79510
1.50,
1.75,
2.00,
2.50
       
  IDF
  79511
1.50,
1.75,
2.00,
2.50
       
  D FI
  79512
1.75
             
  DCN & DCNF
  79514
1.50,
1.75,
2.00
         
  32/36, 40 DFAV
  79515
2.00,
2.50
           
  32/36 DFAV
  79531
1.75.
2.00.
2.50
         
  28/30, 32/36 DGV
                             
  32, 32/36 DGAV
    Picture        
  32/36 DAC
           
           
                         
                              s.rl.
         
                                           
                    Tel. +39 011 8224969 Fax +39 011 8225073 E-mail: ínfo@tecno2.it
           
                                           
In the case of adjustment settings in which the idle fuel jet is separate from the idle air jet, only the value in mm of the latter jet is specified. The idle fuel jet diameter is usually included between 0.40 and 0.70 mm: this jet strongly affects the idle speed mixture metering and thf entire transition (or progression) stage. The idle air jet, instead, comes into play on the higher side of the transition period. By transition stage is intended the carburettor operation range that starts from the idle speed rate and ends slightly beyond the point of main circuit priming.
    and be running at rated operation temperature. Engine idle speed rpm is set by a speed rate adjusting screw to the value specified by the Manufacturer: between 600-800 rpm for touring car engines and about 1000 rpm or more for sports car engines. First, turn in or out slowly the idle mixture adjusting screw to find the position in which it gives the highest possible rpm rate. If the speed must be reduced to the previous mentioned rates, operate on the speed adjusting screw, then check again for proper metering by the mixture adjusting screw. Idle speed mixture is correct when the engine runs smoothly and upon turning in or out the mixture screw - that is, weakening or enriching the mixture strength - the rpm rate drops and becomes erratic.
     
Idle speed circuit feed - Generally, in applications where a single carburettor barrel feeds two or more engine cylinders, the idle speed circuit receives its fuel supply from the main well, in a location between the main fuel jet and the lower end of the emulsion tube (Fig. 38). In sports engine applications where each carburettor barrel feeds a single cylinder, the part-load operation mixture tends to be weak; thus, the idle speed circuit receives its fuel supply directly from the constant-level float chamber (Fig. 37), in the majority o - cases. In some applications, designers prefer a compound system in which the idle jet is fed simultaneously from both the float chamber and the well.
         
    Transition (or progression) stage check - Once the idle speed rate is properly set, increase engine rpm rate by the speed adjusting screw up to the point at which the mixture is about to issue from the auxiliary Venturi spray tube (say, 300 rpm above idle rate): now, check for correct metering by turning slowly in or out the mixture adjusting screw. If by screwing in the speed increases it means that progression is rich while it is weak if the mixture screw must be backed out (open) to obtain a speed increase: progression will instead be correct if by turning the mixture adjusting screw either way the rpm rate will drop. From the results of this check, the transition stage may be enriched by increasing the idle fuel jet diameter or by reducing the idle air jet diameter. It is of course possible to weaken the transition stage by proceeding in the opposite way.
     
                 

               
Engine idle speed rate adjustments
             

               
This brief description must be completed by the more detailed instructions outlined on page 55 under Part Three.
           
The engine must be connected to a revolution counter
           
                                         
41

Sometimes it may prove necessary to re-locate the transition orifice with respect to the throttle valve edge, for instance, when a carburettor servicing includes polishing of the barrel and throttle valve replacement. Such condition is illustrated in Figs. 39 and 40. In Fig. 39-A the transition orifice is blanked out by the throttle plate edge set in idle speed position as it should be for correct operation.
    In Fig. 39-C the transition orifice is offset downwards (downstream of throttle) and idle speed operation is quite "rough" owing to an excessively rich mixture even with mixture adjusting screw tightened in fully (closed), as the supply from the transition orifice is too generous. The remedial actions for such conditions are: - case of Fig. 39-B - by trial and error cut a chamfer in throttle plate edge as shown in Fig. 40-A. - case of Fig. 39-C - drill a hole in throttle plate, on the side opposite the transition orifice, so that part of the air drawn in by the engine will flow through, thus allowing the throttle valve to remain closed, as shown in Fig. 40B. Initially, this hole should have a diameter of 0.7 mm and may be increased gradually up to 1.2 - 1.5 mm, as required, but never to a diameter that would cause the
In Fig. 39-B the transition orifice results offset upwards (upstream of throttle) and though idle speed operation is quite smooth "flat spots" will be experienced as soon as the throttle begins to open, owing to an excessively weak mixture. In fact, in this case the orifice is acted upon too late by the depression existing beneath the throttle plate.
 
                     
 
Picture
   
                     
FIG. 39
               
Transition orifice location with respect to the edge of the throttle set for idle speed operation.
       
A correction location - B location offset upstream resulting in a positive head b - C location offset downstream resulting in a negative head b.
                     
    Picture      
                     
FIG. 40
               
To advance transition orifice action, a slight chamfer is cut in throttle plate (see A) whereas to retard this action a small hole is drilled through the throttle plate (see B).
 

throttle plate to blank out the barrel completely.
        If the pump supply ceases "faltering" accelerations will result with "poppings" in carburettor, followed by possible stopping of the engine. Instead, if the pump supply is excessive, acceleration will still falter and an emission of black smoke at the exhaust will mark each acceleration.
The above procedures serve to remedy slight faults and
       
it is not possible to describe here other corrective
     
measures such as variations in transition orifice location or diameter.
 
Weber throttle valve plates are stamp-marked with a value representing the lowest angle in degrees existing between closed throttle and barrel centreline - usually 78° or 85° - to prevent any replacement errors. 7-8-9) Accelerating pump jet and drain Figs. 41 and 42
   
               
     
Picture
   
The main features of accelerating pump operation are the amount of fuel injected at each stroke and the promptness and duration of each injection. When tuning up for proper adjustment settings, the pump jet and drain diameters are determined by trying to minimise, as far as practicable, the amount of fuel injected. Often, also the direction of the fuel spray proves to be a significant factor. Generally, when engine operates at high rpm rates the pump jet (diameter between 0.35 and 1 mm) is subject to a vacuum sufficient to produce an uninterrupted flow of fuel, that is, it performs as a high speed jet and its role falls under the adjustment setting data.
       
             
  FIG. 41
       
  Accelerating pump jet - Right: the DCOE series carburettor jet.
 
                         
  Picture      
                         
FIG. 42 - A and B
                     
In A the pump jet is incorporated in the intake valve assembly and the diameter of drain F is marked on the part. In B the pump jet is of the separate type - 1 Pump delivery valve - 2 Pump jet - 3 Pump drain - 4 Pump intake valve - 5 Pump diaphragm.
 

The pump drain jet (Fig. 42) which may also be of the type incorporated in intake valve assembly is selected in one of the following two settings: - Closed, for maximum amount of injected fuel and maximum promptness.
    possible adjustments to cope with different engines and starting temperatures. An increase in choke fuel jet bore enrichens the mixture over the entire operation range whereas any variation of the choke air jet is more influential once engine is started and during its warmup period: the setting of the choke system involves several provisions such as the fuel reserve well, the arrangement of blanking element and its intervening action adjustment, a special valve for leaning out the mixture once engine is started, etc., all of which may vary from one carburettor to another. Offset shutter valve choke - Fig. 43-B - shows a manually-controlled starting circuit of the offset shutter (or strangler) valve type. The more significant factors for adjustment settings, and referred to the choke-IN condition, are:
- Open, with 0.35 to 1.5 mm bore, to reduce the amount of fuel and to slightly retard promptness.
     
Using some special provisions it is possible to measure the amount of fuel injected by the pump at every throttle opening: for the adjustment setting considered here, the value in cc referred to a single barrel is tabulated on page 20.
 
                     
     
Picture
       
              - Opening of the main throttle, known as the fast-idle setting: increases the idle speed rate of the engine once it has started and runs through the warm-up stage.
 
              - Calibrated starting spring: it is essential to establish the mixture metering needed through the choke-IN stage. - Stopping of the shutter valve opening to ensure appropriate meterings during warm-up at large main throttle openings.
              Make sure the shutter (or strangler) valve moves freely without any binding caused by distortions, wear or dirt: for a correct adjustment of the manual control - a very important operation to prevent starting or idle speed rate difficulties - refer to the instructions given on page 54 under Part Three.
 
                       
      Picture            
                         
                 
Picture
   
                           
FIG. 43-A
                   
Shows the DCOE series carburettor choke system and jet.
             
1 Constant-level float chamber or bowl - 2 Starting fuel reserve well - 3 Choke jet of the type with incorporated emulsion tube and air jet - 4 Plunger valve.
       

                       

                         
10) Choke jet - Fig. 43-A
                 
The DCOE series carburettor is provided with an easy starting device (choke) of the progressive-action type consisting of two separate circuits (one to each barrel) ìn which two manually operated plungers govern the mixture rating.
         
             
    FIG. 43-B
     
    Shows an offset shutter (or strangler) valve choke system - Position A - Device IN; position B - Device OUT.
   
The choke jet which often incorporates the emulsion jet and the air jet - may have a diameter included between 0.60 and 2 mm, thus permitting a wide range of
  1 Control lever - 2 Rod controlling the opening of throttle 6 at fast idle, through idle lever 3, lug 4 and lever 5 - 7 Idle speed adjusting screw - 8 Calibrated starting spring - 9 Stop limiting the opening of shutter valve 10.

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  11-12) Needle valve
               
  Through the needle valve the float regulates the admission of fuel into the bowl to keep the level constant independently of the variable engine requirements. Level maintenance is improved by adopting needle valves having the smallest diameter that still provides the fuel supply necessary for engine operation at its highest power rating.
         
  One of the more commonly adopted diameters is 1.50 mm which is capable of supplying 25-30 litres per hour of fuel if pressure ranges between 0.15 and 0.20 kg/ sq.cm (2.1-2.8 psi): larger sizes are used for higher fuel consumption rates and fuels containing alcohols.
           
  The needle taper point and seat are finished and checked as a pair and are not interchangeable with the respective parts of other valves. The needle valve is often damaged by engine vibrations and car motions if the float chamber is empty (LPG feed systems); in the case of sports cars transported on trucks, carburettor bowls should be filled with thin engine oil for proper protection. 13) Fuel level in float chamber or bowl - Figs. 44-45
         
                 
    FIG. 45
       
    Fuel level hydraulic checks - 48 IDA type carburettor - 1 Vernier calliper - 2 Flared air horn extension (or additional air intake) 3 Strainer - 4 Main calibrated parts - 5 Fuel arrival line - 6 Flashlight.
 
  The fuel height in bowl must be kept at a lower level with respect to the spray nozzle bore: this prevents fuel
               
    b) Inside the well, after having removed the air jet and emulsion tube, by a Vernier caliper 1 and flash-light 6, as shown in Fig. 45.
             
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  When the end of the gauge rod comes into contact with the fuel in the well it causes a sudden change in the reflected light thus giving a clear indication of the level measurement. This check is possible on almost all sports car carburettors which are often fed by an electrii pump which turns out to be extremely useful on this occasion. Check the float maximum lowering position: the needle must travel a distance equivalent to slightly more than the diameter value (in mm) stamped on its seat. If any correction is needed, bend delicately the twi tongue plates located in proximity of the fulcrum pin. 14) Float-weight
             
  FIG. 44
         
  Fuel level geometrical checks - 40 DCOE 2 type carburettor - C Weber gauge - Sf Valve damper ball.
     
        In the case of the adjustment setting being considered here, the weight is 26 grams because the float is double: the weight in grams is stamped on the tongue plate or float itself and is an adjustment setting specification for it is one of the factors establishing the fuel level in bowl. The metal float is delicate as it is made of 0.16-0.20 mm thick sheet: for this reason, absolutely avoid blowing compressed air into the float chamber or fuel inlet port when float is installed in its place. The free and unimpeded movement of the float in chamber is a design requirement. 15) Flared air horn extensions - Fig. 45 They are necessary in sports car applications where quite frequently no air cleaner is provided. Their purpose is to:
             
  emissions when engine is inoperative and car inclined. The level may be set at a height of less than 5-6 mm below nozzle bottom edge, depending on the type of carburettor and the performance required of the vehicle. Fuel level variations have greater influence during accelerations, idle speed and part-load/low rpm operation, with particularly marked effects in sports car applications. The Catalogue Data Sheet of each carburettor provides the necessary instructions for a correct level check which is performed as follows: a) by a special gauge rod C - Fig. 44 - taking care not to push in the ball of the spring-dampened valve. Usually, the cover gasket is removed if to do this it is unnecessary to take out the float; otherwise, check with gasket tight on cover held vertical.
 
    - Improve cylinder charging
     
    - Limit dispersions due to mixture "rejections" - Carry the flame trap.
   

  Carburettor
                       
                             
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  Series 38-48 DCOE
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Idle Speed Operation
   
             
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