See also in the Sportsterpedia:

• Bendix Carb Basic Information
• Rebuilding the Bendix Carb
• Bendix Carb Functions, Adjustments, Tuning

There are a lot of Sportsters out there that do not have their original Bendix carb attached to them.
Consequently, this page will try to bring to light at least some the differences in these carbs.
One could say it's a blessing that Bendix carbs for Harleys will interchange.
One could also say it's a curse.
Bendix carbs for Sportsters were set up for Sportsters.
Bendix carbs for other HD models were set up for the needs of those motors.
Changing the jetting alone (on other intended model carbs) to Sportster specs may still not give the results intended.
The 27155-72A Sportster carb has another number stamped into the ID pad (13732).
This Bendix part number denotes a certain configuration carb body and / or internal parts.
Change Letters:
You may have noticed a letter beside the HD part number or it may be arbitrarily stamped in the ID pad away from the HD number.
Carbs with changes made during the build phase had the change letter included at the end of the HD stamped part number.
Carbs with changes made at the dealership (customer owned bikes) had the change letter stamped into the existing ID pad…somewhere.
This explains the arbitrary location of some of the change letters.
For example, an “A” stamped into the ID pad away from the HD part# is a Bendix modification letter, not a suffix letter to the HD part#.

Bendix model 13479:

The model 13479 carb was used on FLP, FLH and FX model Harley Davidsons.
The letters A, B, C, D, E and F stamped near the basic Bendix part number (13479) are change letters.
Meaning they denote certain changes made per carb model.

The following changes are noted in Technical Service Bulletin (614A). ⁴⁾

• Change for 13479A:
  • The float setting was changed from 1/8“ to 3/16” to remedy a rich condition occurring at steady speeds.
  • The clearance between the float tang and the wire clip on the needle decreased.
    It should be .005“-.010” between the top of the tang and bottom of the portion of spring that hangs over the tang.
• Change for 13479B:
  • A new choke valve has detents with a spring loaded plunger engaging the detents to provide positive positioning throughout the choking range.
  • New part (27664-71 choke shaft replaces 27664-70.
  • New part 27665-71 plunger added.
  • 27666-71 plunger spring added.
• Change for 13479C & 13479D:
  Changes were made to correct over-rich mixtures in the intermediate (off idle) speed range.
  • A new idle jet has two .06mm holes instead of one .08mm hole near the screw end.
    • New part (27725-71) idle jet has the letter 'A' stamped on the screw end and replaces 27723-71.
    • The idle air bleed hole in the carb body was enlarged from 3.35mm to 3.60mm (app. 9/64: in diameter).
      Idle jet (27725-71 must be used with the drilled out passage in this carb for proper carburetion.
      Dealers could drill the bleed hole and stamp the change letter if there was a problem with the field unit's performance.
    • The accelerator pump shaft had 2 additional holes to allow for an increase or decrease of quantity of fuel delivery.
      Factory setting for the pin was the center hole.

Bendix model 13609 and 13731

There were three Bendix carburetors, designated in the parts catalogs, that were installed on Sportsters.

Bendix model 13732

• 27152-71A (13732) - 38mm, was reportedly factory installed on a '74 XLH delivered from the dealer in July 1974. ¹³⁾

Other known Bendix ID information:

The venturi size is cast into the venturi. ²¹⁾
Looking in the carb from the air cleaner end, the numbers are on the venturi at 12:00 o'clock on the radiused entry.
They are small but every bendix should have the number stamped there.

²²⁾

27155-72 (13609B), arbitrary 'B', venturi stamped 36mm 23)

27155-72B (13731C), arbitrary 'C', venturi stamped 38mm 24)

Both of these carbs are stamped 27152-71.
One has a '36' and the other has a '38' stamped inside the venture.

27152-71A (13732) - venturi stamped '38' 25) 26)

27152-71 (13479A) arbitrary 'A' - venturi stamped '36' 27)

27152-71 (13479E) arbitrary 'E', adjustable jet 28)		27152-71 (13479E) arbitrary 'E', fixed jet, 36mm 29)

Side by side comparison of 36mm and 38mm Bendix carbs.
Aside from the venturi size, the other main difference that might affect the way it runs is the number of secondary idle discharge ports.
These are the holes that get uncovered by the throttle plate at part throttle settings.
The 38mm has 3 (in addition to the idle adjustment screw hole).
The 36 has 2 (in addition to the idle adjustment screw hole).
The air cleaner screw bosses on the 36mm are smaller.

(Left) 38mm, (Right) 36mm 30)	36mm doesn't have a bowl vent hole here 31)	(L) 38mm has a flat corner, (R) 36mm is round 32)

The 13609A 36mm carb has 3 idle passages. ³³⁾
The 13609B 36mm carb has 4 idle passages. ³⁴⁾
The 38mm carbs have 4 idle passages.

One feature of an adjustable main jet, (besides the number), is the holes near the bottom that are drilled at about a 45° angle. ³⁵⁾
Note that on the adjustable main jet shown below (R), the top of it looks identical to the fixed jet. ³⁶⁾

³⁷⁾

Some have converted their fixed main jet setup to an adjustable jet.

The C66-157 fixed main jet came standard on a 1974 Sportster.

Bendix Carb Main Jet C66-157 - 1.10mm 38) 39)

The C66-184 adjustable main jet has the tube extending beyond the taper. ⁴⁰⁾

Bendix C66-184 adjustable main jet 41)

Alternate references include intermediate / idle / low speed jet. The original idle tubes are designated with either an A, B, or C marked on top. ⁴²⁾

Tube sizes:
These are removable (threaded) jets.
Both the A and B tubes were used on the early 27155-72 (13609B) and 27155-72 (13731) carbs.
Neither the screw type “C” tube nor it's successors were ever installed on a Sportster carb (officially anyway).

• A = .60mm ⁴³⁾ (27749-72) standard on carbs through change letter “A”.
• B = .65mm ⁴⁴⁾ (27750-72) standard on carbs through change letter “B”.
• C = ⁴⁵⁾ standard on carbs through change letter “C”.

72-74 Sportster Fixed Idle Tube: (screw in type - no adjustment)
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75-E76 Sportster Fixed Idle Tube: (pressed in type - no adjustment)
Note: Measurements taken on used / removed idle tube from carb #27155-72B (13731C)
^{48) 49)}

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Here’s another, and more significant difference. ⁵³⁾
The cable attachment to the throttle shaft is in a different position which changes the geometry of the cable action.
With the 36 mm carb, the cable pulls from over center with the stock outer jacket bracket.
As you can see in the left picture, even with a modified bracket, the geometry isn’t great.
The picture on the right is the same 36mm carb with the correct throttle shaft and return spring for a 38mm carb added.
The throttle return spring is substantially stronger than the original (for the 36mm).
It also required an additional spring to properly return.
The standard (38mm style) bracket was used to support the outer jacket of the cable.

⁵⁴⁾

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^{60) 61) 62)}

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^{66) 67) 68)}

• Standard Finish ⁷⁰⁾
• 38mm venturi
• Fixed main jet
• Fits all H-D® Sportster 1974 through 1980 engines
• OEM for (27155-72B)

• Standard Finish –38mm -venturi ⁷¹⁾
• Adjustable main jet
• Fits all H-D® Sportster 1974 thru 1980 engines

⁷²⁾

• Standard Finish ⁷³⁾
• 40mm venturi
• Dual throttle cable
• All year H-D® models with use of proper manifold.
• Designed for Evolution® motors

• 015110 – Standard finish ⁷⁴⁾
• 015112 –Chrome finish
• 40mm venture
• Adjustable main jet
• Dual throttle linkage-spigot mount
• Fits 1984 Evolution Engines & H-D Twin Cam models 1999 and later.

Parts listed from the 1962-1973 Sportster Parts Catalog Supplement (99451-73)

• Zenith Fuel Systems.com
• 2009 Zenith Fuel Systems LLC PDF for Harley Carbs