See also 77-85 Oil Pump and Parts (app.) Dims

Oil Pump on 83 XLX 1)

E77:
Special “1600” oil pump stamped with an “O”:
(26484-75) Oil pump body
(26486-75) Pump cover

Late 77-81:
(26484-75) Oil pump body
(26486-75) Pump cover

82-E83:
(26484-83) Oil pump body
(26486-83) Pump cover

L83-85:
(26484-75A) Oil pump body
(26486-75A) Pump cover

See also Gear Shaft Dims.
The gear shaft (26488-75) was used from 77-90.

The dims and teeth pitch are all the same on the gear.
However, there are variations of the exact length of the shaft.

All have 20 teeth gears 2)	Longer shaft (L), Shorter shaft (R) with hash marks on the top. Reason for the hash marks presently unknown. 3)

This shows where the wear occurs. 4)	Lengths slightly different. 5)

See also Gearshaft Pin Dims

(26430-76) Gear shaft pin.
These are solid pins (not to be confused with a roll pin with a hollow core) ⁶⁾

See also;
Inner Plate Dims

The inner plate (26463-77) is the top plate (with the pump installed).
The return gerotors sit on this plate.
It was used in all 77-90 oil pumps.

Inner plate (26463-77). Hole for the gearshaft is off center. Machined step is to locate the spring washer between the two plates. 7)

Inner separator plate installed position. (pump upside down) 8)

See also;
Outer Plate Dims

The outer plate is the bottom plate (with the pump installed). The feed gerotors sit under this plate.

• (26493-75) was used in 77-82 oil pumps.
• (26493-75A) was an upgrade for the E83 pump assembly.
  It also was used in the re-designed L83-85 assemblies as well as all 86-90 oil pumps.

Either will fit 77-90 oil pumps with their respective seals.

Outer plate comparison 9)

77-82 outer plate (26493-75) I.D. 0.518“

77-82 oil pump outer separator plate top view 10)	77-82 oil pump outer separator plate bottom view 11)

83-90 outer plate (26493-75A) I.D. 0.683”

Seal 1

Seal 2

See also;
Gerotor Dims

• There were 2 different sets of gerotors used in Sportster oil pumps from 77-85.
  • 77-E83; Return set (26491-75), Feed set (26492-75).
    Discontinued for production models by November of 1982. ¹²⁾
    Sold for 77-E83 oil pumps through 1984.
  • L83-85; Return set (26491-83), Feed set (26492-83).
• The -78B parts book lists the original gerotors.
  (even though that catalog was written in 1989 after the design change).

The outside gear in each 77-E83 gerotor set was chamfered.
The outside gear in each L83-85 gerotor set was straight cut.

77-E83 gerotor outside edge 13)	L83-85 gerotor outside edge 14)

These can also be used on L83-85 oil pumps. ¹⁵⁾

(26491-75)

77-E83 Chamfered Return Gerotors
(can also be used on L83-85 oil pumps). ¹⁶⁾

• The late 83 oil pump assembly (26197-83) gerotor gears are fabricated without the chamfered top and bottom on the outer diameters as was in the 77-E1983 gerotors.
  This new assembly will retrofit to 77-E83 engines ^{17) 18)}
  The new gerotors will retrofit to the 82 model pump body and cover. ¹⁹⁾
• Late 1983 pump bodies and covers were also under-cut or relieved to accommodate for clearances with the new gerotors.
• The 77-E83 chamfered gerotors have a (.020“ x 45° chamfer or .020”) radius and the same radius is designed into their respective oil pump body / cover.
• The Late 83 pump body and cover has a (.010“ max. radius) undercut for clearance designed into them.
• These modifications limit interchangeability and affect the installation of repair parts:
  • Either early style or late style gerotor gears may be used with late style (under-cut) oil pump bodies and covers.
  • Only early style chamfered gerotor gears may be used with early style oil pump bodies and covers
    (Use of late style gerotor gears in early style oil pump bodies and covers could cause the oil pump to bind up and possible pump failure).

See also;
Check Valve Dims
More on how the check valve works

Made by Circle Seal.
Part # P106-376.
Patent #3626977.
It has an arrow pointing up with FC to the bottom left of the arrow.

• The oil pump check valve plays a role in the operation of the oil pressure switch.
• It also stops oil from entering the engine when the engine is shut off (in theory).
• The check valve had 2 different part numbers.
  • The original was (26435-76) in 1977.
• The part number was upgrade (26435-76A) for L77-78 models ^{20) 21) 22)}
• Speculation could say…,
  • The original check was for the special “1600” pump (discontinued L77).
  • And the upgraded check was for installation in a newer, non publicized, pump casting not cataloged.
• Either way, the upgraded check valve was used through 1985 on IHs.

26435-76A check valve 23)	With the O-ring removed, you can see the crimped 2-piece body design 24)

The check valve sits inside the bore in the pump body as shown. Installed position (R)25)

The closest on the Circle Seal website is a 2900 series cartridge check valve.
Click on the 2900 series in the catalog section to the left on the their site.

In the Products-Engineering-Terminology PDF;

Flow capability (Cv=0.55). Flow capability indication commonly accepted by the valve industry. The literal definition is that a component with a Cv of one (1);
Can flow one (1) gallon of water with a ΔP of one (1) PSI.
The calculated results from Cv equations must be considered reasonable approximations only.

Link to the Circle Valve site with comparable dims and specs:
https://catalog.circlevalve.com/item/check-valves/c2900-series-cartridge-check-valve-0-to-3000-psig/cs-c2949b-4q
This one has a back-up O-ring on the valve.
That link came from this XLF thread:
http://xlforum.net/forums/showthread.php?t=1979566&highlight=gerotor&page=2

See also;
Tesing the Oil Pressure Switch
More on How the Ironhead Oil Pressure Switch Works

(26554-77) Oil pressure switch (L-77 to 90).

On 77-85 models, it was mounted at the oil pump and later mounted to the filter pad on 86-90 models.
The oil pressure switch was listed in the -77A parts supplement catalog.
However, it was listed as a L77 addition in the -78 parts supplement.
The circumstance of this switch being a late addition is unclear.
However, there was a wiring harness upgrade in 78 and an oil pressure gauge available for 77-78 models.
Double nuts (7638) for the oil pressure switch were also a late addition part #.
(retainer for the wire to the oil light)