See also in the Sportsterpedia:

• Keihin Butterfly Carb Basic Information
• Rebuilding a Keihin Butterfly Carb
• Keihin Butterfly Carb Function and Tuning

Sportster '76 only' Keihin butterfly carb.
It has a solid choke, meaning that the choke plate (butterfly) has no spring action in the linkage. ¹⁾
You can begin to identify -76 only carb cause there is no plastic pieces on the choke shaft.
It also has a idle mixture adjusting screw that was not hidden under a plug. It was rite out in the open where you can get to it.
That is what you can tell from the outside.
²⁾

The real scoop to tell if it's -76 is on the inside.
Inside, there was no hole drilled between the main jet well and the low speed well to feed the low speed jet.
That made it the only one that didn't use the low speed jet rubber plug you see when you take off the float bowl.
This hole can be seen when you remove the rubber plug and look at the wall between the wells on 77 and up Keihin butterfly carbs.
77-up carbs have a hole to connect the low speed well to the main well. 76 only had no hole.
If you have a 76 only and install rubber plug, your bike won't run.
In the float bowl, the accelerator pump discharge nozzle has a .040“ orifice, (stamped 100), as apposed to the .031” (stamped 75) used on 77 up.
But most importantly, it didn't have an accelerator pump “relief” port. You can observe the relief action (if you have a 77-up bowl).
Remove the bowl and the “L” shaped linkage that actuates the pump. Drop the “L” into its hole on the side of the bowl.
Pour enough fuel in the bowl so that you have it about 1/4 full and actuate the pump by depressing the “L” link (don't squirt on yourself).
On the 77-up, there is a little hole down on the bowl floor that fuel squirts out of, as well as the brass nozzle at the gasket surface.
The quicker you press, the more goes thru the “relief”.
All “relief” bowls have a steel rod installed under the discharge nozzle. This rod is free in its movement and you can hear it if you shake the bowl.
This rod acts as “variable” resistance to fuel flow to the actual discharge nozzle.
If the pump is actuated slowly enough, all fuel will exit the relief because there isnt enough force to lift the rod.

'76 only' didn't have the rod at all. Instead, it used a check ball assembly in the small cover that is screwed onto the bowl (the one with the 3 holes).
When you shake the small cover when it's removed from the bowl, you will hear the ball. There is no ball on 77-up.
'76 only' has even more differences but those are the biggies.

The JP Cycles Deluxe Carb Rebuild Kit (4000050) will work. ³⁾

L76 (only) XLH, XLCH main jet 140, slow jet 100,

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Sportster XLH, XLCH, XLT Keihin Butterfly carb.
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Sportster XL, XLCH, XLS models, main jet 165, slow jet 65, limiter cap over the idle mixture screw.
¹²⁾

81-E82 XL, XLS.
Main jet 160, slow jet 68.
Soft plug over the A/F mixture screw.

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83 XL, XLS, XLX E1983.
Main jet 160, slow jet 68.
Soft plug over the A/F mixture screw.
Black plug over evaporative port.
¹⁵⁾

There are usually lots of compatible Keihin carbs on eBay. Anything from late 1976 up to about 1988 will bolt on and work well. ¹⁶⁾
They all “look” about the same but there are differences. (As for factory Sportster carbs), best may be the late 1976 to 1978 keihin butterfly.
It is 38 mm, and does not suffer the government mandated modifications that are in the 1979-on Keihins.

Application for all 76-E1978 FX models. ¹⁷⁾
No choke spring, no plastic on choke. ¹⁸⁾
Air Fuel Screw is on top, not buried under a cap.
Accelerator pump has check ball, not the rod.
Low speed jet is covered with rubber plug and there is a hole between the low speed and main well.

¹⁹⁾

L1978-1979 FX, FXE, FXS
²⁰⁾

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This is reportedly a 1980 Shovelhead carburetor. ^{24)
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This was the factory carb mounted to a 1979 FXS / FXEF-80, main jet 160, low speed jet 72.
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1981-1983 FXEF-80 / FXE-80

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Part number unknown at this time, BT carb . Possible 83 model carb due to the black rubber cap on the top of the carb's evaporative port. ^{39) 40)}
Just leave it capped. It has no practical use.
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All 1987 FXR, Softail models, main jet 162, slow jet 50
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Other numbers on body: (0695) and (F58A) (BH28) for 88-89 FLT, FXR and SOFTAIL models (except Cal.) ⁵⁹⁾

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Body casting (0565) and (F59B) for 88-89 FLT, FXR and SOFTAIL models (Cal. and Swiss models only) ⁶⁵⁾

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Video:
Here are some excellent videos of servicing the pre-CV Keihin Butterfly carbs:⁶⁷⁾

• #1 - Tips and tricks.
  
• #2 - Disassembly and cleaning.
  
• #3 - Assembly and testing.
  
• #4 - Testing and start-up.