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Wiring Color codes HS4/HS2  carburettors by year
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         Carburettors Models by year

 

   HS4/HIF4 Carburettors as fitted to MG B Series engine          
     
Dual 1-1/2" throat carbs on the 1800cc engine                                       

model year model
name
Carb
model
Std.
needle
rich
needle
weak
needle
needle
mounting
Needle
Guide
Needle
Screw
Piston spring Throttle
disk
1968 MGB (USA) AUD265
(HS4)
AUD1530
(FX)
    fixed   AUC2057 AUC4387
(red)
 
68-69 MGB MKII
(USA)
AUD326
(HS4)
CUD1004
(AAE)
    biased AUD4288 AUD4251 AUC4387
(red)
WZX1329
70-71 MGB MKII
(USA)
AUD405
(HS4)
CUD1004
(AAE)
    biased AUD4288 AUD4251 AUC4387
(red)
WZX1329
71 MGB MKII
(USA)
AUD465
(HS4)
CUD1010
(AAL)
    biased AUD4288 AUD4251 AUC4387
(red)
WZX1329
72 MGB AUD492
(HS4)
CUD1018
(AAU)
    biased AUD4288 AUD4251 AUC4387
(red)
WZX1323
72 MGB MKII
(USA)
AUD493
(HS4)
CUD1018
(AAU)
    biased AUD4287 AUD4251 AUC4387
(red)
WZX1329
72-74 MGB MKII
(USA)
AUD550
(HS4)
CUD1027
(ABD)
    biased AUD4287 AUD4251 AUC4387
(red)
WZX1329
74 MGB
(USA)
AUD630
(HS4)
CUD1027
(ABD)
    biased JZX1039 AUD4251 AUC2107
(lt blue & blk)
WZX1329
65-66 MGB & GT AUD135
(HS4)
AUD1004
(#5)
AUD1005
(#6)
AUD1008
(#21)
fixed     AUC4387
(red)
WZX1323
67-68 MGB & GT AUD278
(HS4)
AUD1530
(FX)
AUD1004
(#5)
AUD1473
(GZ)
fixed     AUC4387
(red)
WZX1323
69-71 MGB AUD325
(HS4)
AUD1530
(FX)
AUD1004
(#5)
AUD1473
(GZ)
fixed     AUC4387
(red)
WZX1323
72 MGB AUD434
(HIF4)
CUD1018
(ABD)
    biased AUD4287   AUC4387
(red)
WZX1323
73-74 MGB
(ECE)
AUD616
(HIF4)
CUD1018
(ABD)
    biased AUD4287   AUC4387
(red)
WZX1329
74-76 MGB
(ECE)
FZX1001
(HIF4)
CUD1051
(ACD)
    biased AUD4287   AUC4387
(red)
WZX1329
76 MGB FZX1229
(HIF4)
CUD1051
(ACD)
    biased AUD4287   AUC4387
(red)
WZX1329
   Note: 1.)   ## signifies throttle valve has a poppet valve on it
            2.)  Rich/Lean needles are elevation/atmosphere changes not

                                                 

   HS2 Carburettors  as fitted to MG A Series engines
       Dual 1-1/4" throat carbs on the 1275cc engine

model year model
name
Carb
model
Std.
needle
rich
needle
weak
needle
needle
mounting
Needle
Guide
Needle
Screw
Piston spring Throttle
disk
67-68 Midget MkIII AUD136
(HS2)
AUD1478
(AN)
AUD1242
(H6)
AUD1211
(GG)
fixed   AUC2057 AUC4587 WZX1320
68-71 Midget MkIII AUD327
(HS2)
AUD1478
(AN)
AUD1242
(H6)
AUD1211
(GG)
fixed   AUC2057 AUC4387 WZX1320
71-72 Midget MkIII AUD502
(HS2)
CUD1017
(AAT)
    biased AUD4288 AUC4250 AUC4587 WZX1380
73-74 Midget MkIII
(ece)
AUD662
(HS2)
CUD1002
(AAC)
    biased AUD4288 AUD4250 AUC4587 WZX1320
68 Midget MkIII
(USA spec)
AUD266
(HS2)
AUD1478
(AN)
    fixed   AUC2057 AUC4587 WZX1383
68-69 Midget MkIII
(USA spec)
AUD328
(HS2)
CUD1002
(AAC)
    biased AUD4288 AUD4250 AUC4587 WZX1383
69-70 Midget MkIII
(USA spec)
AUD404
(HS2)
CUD1002
(AAC)
    biased AUD4290 AUD4250 AUC4587 WZX1383
72-74 Midget MkIII
(USA spec)
AUD549
(HS2)
CUD1026
(ABC)
    biased AUD4288 AUD4250 AUC4587 WZX1322
                     
Note:     1.)  ## signifies throttle valve has a poppet valve on it
            2.)  Rich/Lean needles are elevation/atmosphere changes not

   notes:

1. needle numbers are mfr (SU) part numbers. the second number/letters are the markings on the needles.
2. Weak needles are for adjustment at higher elevations and do not necessarily represent an increase in economy.

 

        Selecting the proper needle for any modifications to the stock configuration can be a real nightmare. There is a program that will help you select the proper needle you need, based on you testing. How do you test? There are a few different ways. At the extreme 'cheap $$' end of the spectrum... is the cruise test. No special tools required, just your eyes. At the other end of the spectrum...is your local service station that has a 'rolling road dyno' to have it tested.

        Suggested method: (Proceed at your own risk!)
Find a relatively deserted section of road. Cruise along in top gear at 20 MPH for about ten minutes or so. Pull over, get out and pull your spark plugs and look at them. Compare them to what they should look like. Write down on a chart what they look like. Repeat this test at 30 MPH, 40, 50, 60, 70, MPH (stay legal now... tickets are YOUR fault not mine). Record what the plugs look like.   Black or sooty, too rich. Gray to light brown, just right, white or ash covered, too lean. As an approximation, the three fattest section of the taper (called 'stations'), cover the idling to 10 MPH range. Thickness' 4-10 cover (non-linearly) 10-80 MPH and hard acceleration mixtures. 9 and up cover sustained wide open throttle.

       Now using the SUNeedle.exe* program, you can compare needle sizes to find the right taper profile that matches the ranges you need to correct. Read instructions for the program. It's not that hard to use. The link above, will download an executable that will un-archive itself into the directory where you store it after downloading. It's an old DOS program but runs fine under newer operating systems.

   Best of luck !                          

  * (The SU needle program has been stored locally on this site to facilitate ease of retrieval for more people. I do not claim any credit or responsibility for its development or use. It just happens to be one of the best tools found, to help in selecting needle types.  My sincere Kudos go out to the author of this fine program!)                     


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last edited 12/06/09

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