IH: Carburetor, Intake Manifold & Exhaust - Sub-01P



Keihin Butterfly Carb Identification

See also in the Sportsterpedia:


76-78 Keihin carbs do not have an HD number on it or a stamp pad for numbering. The Keihin number is stamped in the flange.
The best way to identify a 79-up Harley Keihin carb is to read the Keihin number.
It's the first 4 characters stamped on the (R) choke cable side just above the bowl.
The HD part number on some models is on a sticker placed on the top of the carb.
Older carbs either weren't labeled or the sticker may either be missing or unreadable.

As for interchangeability between butterfly carbs;
Any Harley Keihin butterfly carb will interchange but the ones for big twins will need to be re-jetted for a Sportster engine.
The chart on the Basic carb information page has the factory jetting information for Sportsters.
You may have to go up or down from there depending on what's already in your carb and your specific engine/A/C/exhaust setup.

Also, 76-78 Sportster carbs have a 38mm venture (measured at the smallest point near the throttle plate).
79-87 Sportster carbs have a 34mm venture. However, the carbs installed on BT's may be 38mm.
To find the venture size of the one you have, cut a piece of cereal / kleenex box cardboard 34mm wide and insert it into the most narrow part of the venturi. 1)
Tight fit = 34 mm, loose fit = 38 mm.

See the pics below for a visual confirmation of year model features.



Late 1976-Early 1978

  • Features:
    • 38mm venture 2)
    • Pump adjusting screw
    • Idle mixture Screw
    • Throttle stop screw
    • Rocker arm
    • Intake manifold ( 27021-71A )3)
    • Accelerator pump rod attached at throttle cam 4)
    • 1977
      • New diaphragm accelerator pump 5)
      • Optional main jets were made available 6)

Late 1978-1980

Changes were made to L78-up carbs due to the U.S. Clean Air Act of 1978.

  • Features/ Upgrades:
    • Changed to 34 mm venture 7)
    • Fast idle cam
    • Limiter Cap (over idle mixture )-late 1978-1979
      Square block behind the idle mix tower as a stop for the limiter cap.
    • Throttle stop screw, throttle lever
    • Choke plate
    • Choke lever shaft
    • Mounting flange
    • Accelerating pump lever
    • Rocker arm
    • Intermediate lever
    • 1979
      • Optional high altitude modification kit
      • Accelerator pump housing redesigned 8)
      • Fast idle cam
    • 1980-up
      • Idle mixture screw is set and sealed off at the factory due to EPA regulations 9)

1981-1983

  • Features/ Upgrades:
    • 34mm venture
    • A second cable added at the throttle (idle cable)
    • Throttle lever
    • Throttle stop
    • Fast idle cam
    • Fast idle cam adjusting screw
    • Accelerator pump
    • 1983
      • VOES port
      • Evaporative port
        Note:
        For those sold for use in California (as part of the evaporative emissions kit) the fuel overflow fitting was capped and the overflow line was removed. 10)

1984-1985

  • Features/ Upgrades:
    • 34mm venture
    • Dual throttle cables
    • Throttle lever
    • Throttle lever stop
    • Voes vacuum port
    • Fast idle cam
    • Fast idle cam adjusting screw
    • VOES port
    • Evaporative port

Sportster Keihin Butterfly Carbs

(B50A)

L1976 27153-76 Sportster '76 only' Keihin butterfly carb.
Float bowl (27359-76).
Accelerator pump (27364-76), inside casting# (1-2).
It has a solid choke, meaning that the choke plate (butterfly) has no spring action in the linkage. 11)
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.
12) 13)

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. 14)

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

15) 16) 17)

(B50B) - (B50C)

1977-1978 27153-77 Sportster XLH, XLCH, XLT Keihin Butterfly carb.
Float bowl (27384-77).
Accelerator pump (27364-76), inside casting# (1-2).
18) 19)

20) 21) 22)

(B83A) - (B83B)

1979 Sportster 27469-78,23) 27469-78A 24) XL, XLCH, XLS models, main jet 165, slow jet 65, limiter cap over the idle mixture screw.
Float bowl (27890-78) (B78A).
Accelerator pump (27891-78). Accel pump 27891-80 was sold in 1985 as a replacement on carb 27469-78A. 25)
Idle mixture screw tower has a block made on the back ofit as a stop for the limiter cap.

B83A:
26)

B83B:
27) 28) 29) 30)

(B83D)

1980 XL, XLS 27469-80, 31) 27469-80A 32)
Main jet 165, slow jet 65.
Float bowl (27890-78) (B78A).
Accelerator pump (27891-78). Accel pump 27891-80 was sold in 1985 as a replacement on carb 27469-80A. 33)
Soft plug over the A/F mixture screw.

(B83E)

E1981-E1982 XL, XLS 27469-81 34) 35)
Main jet 160, slow jet 68.
Soft plug over the A/F mixture screw.
Float bowl(27890-78) (B78A).
Accelerator pump (27891-78).

(B83F)

L1981-E1982 XL, XLS 27469-81A. 36)
Main jet 160, slow jet 68.
Soft plug over the A/F mixture screw.
Float bowl (27890-78) (B78A).
Accelerator pump (27891-80).

37) 38)

(B83G)

L1982 XL, XLS 27469-82. 39)
Main jet 150, slow jet 68.
Soft plug over the A/F mixture screw.
Float bowl(27890-78) (B78A).
Accelerator pump (27891-80).

(B83H)

Float bowl (27331-83) (B83H). Casting marks inside the bowl: 328:1
Accelerator pump (27891-80).

E1983 27469-83 XL, XLS, XLX. 40)

L1983 27469-83A XL, XLS, XLX. 41)
Main jet 160, slow jet 52.
Soft plug over the A/F mixture screw.
Accelerator pump (27891-80).
Black plug over evaporative port.
42)

(B83K)

1984 27469-83B XL, XLS, XLX.
Main jet 160, slow jet 52.
Soft plug over the A/F mixture screw.
Black plug over evaporative port.
Float bowl (27331-83) (B83H). Casting marks inside the bowl: 328:1
Accelerator pump (27891-80).

43) 44) 45)

(B83K)

1985 27469-83C XL, XLS, XLX
Main jet 160, slow jet 52.
Soft plug over the A/F mixture screw.
Float bowl (27331-83) (B83H). Casting marks inside the bowl: 328:1
Accelerator pump (27891-80).
Black plug over evaporative port.

46)

Other HD Keihin Butterfly Carbs

There are usually lots of compatible Keihin carbs on eBay. Anything from late 1976 up to about 1988 will bolt on and work well. 47)
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.

27155-76A

Application for all 76-E1978 FX models. 48)
No choke spring, no plastic on choke. 49)
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.
Float bowl: 50)
76-E77 (27359-76).
L77-78 (27359-76A).
Accelerator pump 76-78 (27364-76). 51)

(B28K)

(B81B)

27468-78A.
L1978-1979 FX, FXE, FXS
55)

56) 57) 58)

(B8?D)

27467-80.
This is reportedly a 1980 Shovelhead carburetor. 59)
60) 61) 62)

(B78B)

63)

(B78E)

(B79A)

27472-79.
This was the factory carb mounted to a 1979 FXS / FXEF-80, main jet 160, low speed jet 72.
67) 68)

69) 70)

(B79B)

(B79E)

(B79F)

27472-81A.
1981-1983 FXEF-80 / FXE-80

81) 82) 83) 84)

27029-86

1988 FLT or FXR. 38mm venture. 85)
86)

87) 88) 89)

(02BP)

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. 90) 91)
Just leave it capped. It has no practical use.
92) 93) 94)

95) 96) 97)

98) 99) 100)

101) 102) 103)

104) 105) 106)

(02BQ)

(02BR)

27029-86B.
All 1987 FXR, Softail models, main jet 162, slow jet 50
109) 110) 111)

27029-88

Other numbers on body: (0695) and (F58A) (BH28) for 88-89 FLT, FXR and SOFTAIL models (except Cal.) 112)

113) 114) 115)

116) 117) 118)

(F59B)

27026-88A.
88-89 FLT, FXR and SOFTAIL models (Cal. and Swiss models only) 119)

120)

(F20Q)

Helpful Links

Video:
Here are some excellent videos of servicing the pre-CV Keihin Butterfly carbs: 125)




3)
HD Sportster Parts Catalog (99451-78B)
4) , 5)
HD XLH XLCH-1000 Parts Catalog (99451-78B)
6)
HD Parts and Accessories Bulletin dated February 8, 1977
8)
HD Sportster Parts Catalog pg 17
9)
HD Service Letter #ML-131 dated September 14, 1979
10)
HD Service Bulletin #M-905 dated August 26, 1985
23)
1979 HD Sportster Parts Catalog -79 pg 17
24) , 31)
1980 HD Sportster Parts Catalog -80 pg 17
25) , 33)
1979-1985 HD Sportster Parts Catalog -85 pg 23
32)
1981 HD Sportster Parts Catalog -81 pg 19
34)
1981 HD Sportster Parts Catalog -81 pg 21
35) , 36) , 39)
1983 HD Sportster Parts Catalog -83 pg 23
37) , 38)
photo by terd ferguson of the XLFORUM http://xlforum.net/forums/showthread.php?t=1515905
40) , 41)
1984 HD Sportster Parts Catalog -84 pg 27
46)
photo by hcrashster of the XLFORUM http://xlforum.net/forums/showthread.php?t=1786621
48)
1971-1984 HD FX Model Parts Catalog pg 31
50) , 51)
1970-1978 HD Electra Glide and Super Glide Parts Catalog pg 17
52) , 53) , 54) , 78) , 79) , 80)
63)
photo by pan-shovel-head51-79 of the XLFORUM
71) , 72) , 73) , 74) , 75) , 76) , 77)
107) , 108)
photo by Maustarman of the XLFORUM http://xlforum.net/forums/showthread.php?t=2020910
125)
Used by permission - SportsterPaul at the XLForum - http://xlforum.net/forums/showthread.php?t=2055701
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