From 1986-1987, the stock Sportster carburetor was a Keihin 34mm, fixed-venturi “butterfly” model, as used on the Ironhead models from 1979 onward (BT models still used the 38mm version). Contrary to popular folklore, all Keihin non-CV carbs did come with accelerator pumps.

In 1988, the stock Sportster carburetor was upgraded to a Keihin 40mm, slide-type, constant-velocity model. It was quickly discovered that the lack of an accelerator pump was a shortcoming. To help that situation, a special needle, identified as 27094-88 or N65C, was used to help off-idle performance in the 1988 models, which still had no accelerator pump.

In 1989 and thru 2006, the Keihin CV40 carburetors were produced with an accelerator pump to smooth out initial throttle response.

See also in the Sportsterpedia:

• Keihin Butterfly Carb Basic Information
• Rebuilding the Keihin Butterfly Carb
• Keihin Butterfly Carb Identificaton
• See TSB #694 for introduction information on the Keihin butterfly carb.
  Click the link to view the TSB page in the Sportsterpedia. Then click on the “Y” next to #694 to view / download the PDF.
  

• The Keihin non-CV carburetor is a horizontal type with a fuel bowl, single ring-shaped float, an accelerating pump, idle mixture adjusting needle and a throttle stop screw for speed adjustment. ¹⁾
• The throttle body casting contains an integral venturi and a fuel valve seat that is pressed into the body. The underside of the throttle body contains a boss. The main jet screws into the boss and holds the bleed tube in place.²⁾
  • Operation: Fuel from the gas tank passes through the fuel valve, onto float chamber. The fuel entering causes the float to rise until it shuts off the fuel valve, stopping the flow at a level predetermined by float level setting. ³⁾
  • Idle or Slow System: The slow system functions at idle, low and intermediate speeds when throttle valve is closed or only partially open. At idle, fuel enters the main jet and, after being metered there, enters the slow jet where it is metered again. Fuel from the slow jet enters the slow jet bleed tube where it mixes with air through the slow air passage. Fuel mixture is regulated by adjusting the idle (low speed) mixture screw. When the throttle valve is closed, fuel mixture flows into the venturi almost entirely through the idle port. As the throttle valve gradually opens, fuel mix discharge is transferred to the bypass. The slow jet bleed tube is actually a part of the slow jet. ⁴⁾
  • The Main System: The main system functions at intermediate and high speeds as the throttle valve opens further. Fuel is metered by the main jet and enters the main jet air passage. The fuel/ air mixture then exits from the main nozzle and into the venturi. ⁵⁾
  • The Accelerating Pump System: The accelerating pump system works with sudden throttle openings (rapid acceleration) to quickly inject fuel into the carb to provide extra fuel for the engine demand. Rapid throttle action pushes the pump rod down, flexing the diaphragm, which compresses fuel underneath the diaphragm, forcing it up past the check valve and out the pump nozzle into the venturi. The check valve prevents backflow while the pump nozzle meters the flow. Spring action then returns the diaphragm back to it's original position. As the diaphragm returns, a new supply of fuel flows in and under it so the system will be ready to repeat the cycle with the next rapid throttle action detected. ⁶⁾
  • The Choke System: The choke is manually set by pulling out on the choke button. Pulled all the way out is fully closed (for cold engine), partially open (for warm engine) or pushed all the way in, fully open (for warm engine). ⁷⁾
• Dual throttle cables
• Integral Float Chamber
• Manual Choke
• 3 different models
• 1976L-1978 have 38mm Venturi
• 1979-1987 have 34mm Venturi
• Model Year Changes

1986-1987 Features ⁸⁾

• 34mm Venturi
• Horizontal, gravity fed with a float operated inlet valve
• Throttle stop screw
• Fast idle cam
• Choke system with fast idle adjustment
• Accelerator pump
• Designed to control exhaust emissions
• Fixed jets
• Factory preset idle mixture
• 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. ⁹⁾

Note: Carb B83H was also used on 1983 Sportster models.
See a full list of all known Harley Keihin butterfly carbs here Sportster Keihin Butterfly Carburetors by Year Model in the ironhead section of the Sportsterpedia.

• Main & Slow jet sizes are the same (86-87) 883 & (86) 1100. BUT - Due to internal differences, the carbs are not interchangeable ¹³⁾
  
• Main Jet
  • 27087-80 - 1.50mm
  • 27098-78 - 1.55mm (std)
• Slow Jet
  • 27329-83 - .52mm

Interesting discussion here: https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/172520-stock-carb-size-on-1100-sportster?t=1847273

Harley-Davidson motorcycles equipped with some Screamin’ Eagle® high-performance engine parts may not be used on public roads.
(and in some cases must be restricted to closed course competition)
This engine related performance part is intended for racing applications and is not legal for sale or use in California on pollution controlled motor vehicles.

• Used in the Screaming Eagle Package line from HD as an Evolution XLH HI-FLO Carburetor & Air Cleaner. The carb was a (27001-88)
• The kit Number is 29081-90C for 86 and later Sportsters. Carb stamping is (27FA) plus a 4 character date code.
• Adjustable Accelerator Pump stroke
• Incorporated a special intake manifold to carb spacer that had to be drilled and tapped (1/4 x 28) in the side for included Voes connection adapter
• Required a 1987 replacement style intake manifold for 1988 and up models
• Required possible grinding of the right rear corner of the front cylinder head, due to interference with the carburetor throttle pulley and cable guides, for proper clearance ¹⁶⁾
• Build kits and the bowl gasket are obsolete and hard to find.
  • The bowl gasket (27013-85) has been found at JW Boon.com but not the build kit.
    Click here for a Link to their add. However, they do not ship to the U.S.
  • Dennis Kirk sells a kit that looks to have the correct bowl O-ring included under Parts Unlimited branding. Kit (1003-1671).
    Click here for the link. However, according to the Q&A at the bottom of the page, the O-ring doesn't fit the SE carb. That needs to be verified.
  • Parts Unlimited shows kit# 175288 (1003-1671) as a replacement for the stock paper gasket on Yamahas, still a Keihin though and the gasket (O-ring) looks the same.
    Click for the link
  • Speed Supplies.com has a listing for the bowl O-ring (27013-85) although there is no pic of it. ¹⁷⁾
    Click here for the link

¹⁸⁾

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• Keihin CV Carb Identification
• Rebuilding the Keihin CV Carb
• Keihin CV40 Carb Functions, Adjustments, Tuning

• Constant velocity, gravity fed - has a float-operated inlet valve and a vacuum-operated variable venturi (movable slide).
• Both the CV40 and CVK carbs are made by Keihin in Japan. But only the CV is specific to a Harley and has the bar and shield and HD name on the side. ²¹⁾
  CVK is for Kawasaki and various other makes that contracted Keihin for that carburetor.
  There is also a CV40 making the rounds that is distributed by a Florida company that looks identical but not all the specs match up.
  There is no guarantee that any part (original or CVP) will fit those knock-off carburetors.
  If your CV carb does not have the name Harley Davidson cast above the bowl on each side it is a knock-off.

• The carburetor atomizes gas in proper proportions to the air pulled in through the air intake. The throttle plate controls the amount of air flow. At idle, a small amount of gas is siphoned through the pilot jet by the incoming air and fed thru the Idle Port on the engine side of the throttle plate. As the throttle plate is opened farther, the air begins siphoning gas through the transfer ports (which are fed by the Pilot Jet) and eventually pulls gas thru the needle jet (which is fed by the main jet). The tapered needle, which moves up and down thru the fixed diameter needle jet, increases the flow of fuel as it is lifted up since it's taper gets smaller inside the needle jet, thus allowing for more flow when lifted up and out. The vacuum, in the air filter side of the throttle plate, is used to lift the slide barrel & needle jet. At full throttle, the carburetor venturi is fully opened and the needle is lifted far enough to allow the main jet to flow at full jet capacity. The choke circuit is actually an enrichment valve system to allow more fuel at startup. With the choke knob pulled out, a separate jet opening sends a stream of gas into the carburetor's venturi, on the engine side of the throttle plate, thus enriching the gas/air mixture when the engine is cold. The accelerator pump circuit injects a fine spray of gas into the carburetor intake during sudden twisting of the throttle to aid acceleration & reduce engine hesitation.

by Almond farmer: ²²⁾

• There were no HC emissions changes from 1981-2003 @ 2.5 g/km .
  • 78-79 is 14 g/km
  • 80-81 is 5 g/km
• Any carburetor can meet those standards
• In 2004 CARB went to 1.4 g/km and EPA (49 states)in 2006, last year for XL carburetor.
• CA is the only state in the country with its own emissions standards which are currently the same as the EPA standards.
• In 2008 CARB mandated only .8 k/km HC and EPA with the same requirement, followed two years later in 2010.

The above #s are combined HC + NOX

• Noticed the Keihin 40mms CV used 160 main jet for the 883 up to 2003, then 2004-2006 went to 175 (1.75mm) for 49 state bikes, not CA bikes.
• This change makes the air/fuel mixture run richer, therefore, a richer mixture results in lower combustion temperature with resulting lower HC +NOX to meet more stringent emission standards.
• Notice the 49 state 1200 used 170 jet up to 2004, 180 main jet (MJ) in 2004, & 185 MJ in 2005-2006.
• CA 883 went from 170 MJ to 2003 then changed to 180 MJ in 2005-2006.
• Again making the air/fuel ratio richer.
• CA 1200 cc went from 160 MJ in 1989 to 185 MJ in 2006. So, the 2006, 1200 evo with Keihin 40mms CV with vertical needle used the same main jet (1.85mm)for all 50 states, since CARB & EPA had the same emission requirements on the MoCo in that time.
• Note that jets are selected for operation at below 4000 ft elevation.
• If installing CV to 1000cc IH would first select 170 main jet below 4000 ft elevation. This Keihin CV should return lower emissions than any of the Keihin Butterfly carburetors and even satisfied the tier 1 CARB emissions requirements.
• Unfortunately, CV could satisfy tier 2 emissions at only .8 g/km.

• All CV models come equipped with accelerator pump unless noted.
• All data below is compiled from HD Parts Catalogs unless otherwise noted.
• Sportster models are divided into 3 categories: Domestic, California & HDI models
• See also:
  • California models
  • HDI models
• See Discrepancies in the FSM(s) / Parts Catalog(s) for further information on highlighted * areas in the carburetor charts below
• See also Pics of Keihin CV Carbs That Were Factory Installed on Sportsters

Example Parts Shown Here »>


All CV40 carbs use the following parts & P/N:

27100-88 - Needle Jet (.114“ ID)²³⁾
27101-88 - Emulsion Tube (Needle Jet Holder)
27585-88 - Vacuum Slide (Vacuum Piston)

• All CV models come equipped with accelerator pump unless noted.
• All data below is compiled from HD Parts Catalogs unless otherwise noted.
• Sportster models are divided into 3 categories: Domestic, California & HDI models
• See also:
  • Domestic models
  • HDI models
• See Discrepancies in the FSM(s) / Parts Catalog(s) for further information on highlighted * areas in the carburetor charts below
• See also Pics of Keihin CV Carbs That Were Factory Installed on Sportsters

Example Parts Shown Here »>


All CV40 carbs use the following parts & P/N:

27100-88 - Needle Jet (.114” ID)²⁷⁾
27101-88 - Emulsion Tube (Needle Jet Holder)
27585-88 - Vacuum Slide (Vacuum Piston)

• All CV models come equipped with accelerator pump unless noted.
• All data below is compiled from HD Parts Catalogs unless otherwise noted.
• Sportster models are divided into 3 categories: Domestic, California & HDI models
• See also:
  • Domestic models
  • California models
• See Discrepancies in the FSM(s) / Parts Catalog(s) for further information on highlighted * areas in the carburetor charts below
• See also Pics of Keihin CV Carbs That Were Factory Installed on Sportsters

Example Parts Shown Here »>


All CV40 carbs use the following parts & P/N:

27100-88 - Needle Jet (.114“ ID)⁴⁴⁾
27101-88 - Emulsion Tube (Needle Jet Holder)
27585-88 - Vacuum Slide (Vacuum Piston)

Upon perusing 1986-2006 Parts Catalogs for carburetor information, it's clear that the MoCo was trying to save space in these books at the expense of legibility. Below is a chart showing the initial intentions on the top and the MoCo's mis-interpretations on the bottom. They give no notations (from year to year book) on any changes to the nomenclature. I.E. one way to display a year/ model number is displayed differently in other year books. This chart is not complete nor factual in numbering but as an example only. For instance:

Found and documented discrepancies are in the chart below. I'm sure I didn't list them all ⁵⁶⁾