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 gear dims and teeth pitch are all the same nominally from 77 to present oil pumps.
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)

Gear shaft retaining ring (26497-75) was used on 77-90 model oil pumps.
It keeps the inner plate, return gerotors and gearshaft locked in the pump.
It also sets the lowest position for the plate and return gerotors inside the pump.

Gear shaft retaining ring (26497-75) 6)	Installed location 7)

See also Gearshaft Pin Dims

The gear shaft solid pin (26430-76), not to be confused with a roll pin with a hollow core ⁸⁾, was used in 77-90 oil pumps.
The diameter and lengths of the pins vary.
The shaft pins don't have to run out and touch the gerotors.
They simply turn both gerotors at the same time.
So, the exact length shouldn't be an issue.
The lower pin also holds the outer plate in the pump body.

Gear shaft solid pins. (26430-76)9)	Pins installed in the gearshaft. 10)	How the pin sits inside the gerotor. 11)

Lower shaft pin installed 12)

The 77-90 oil pumps used two plates to separate the feed and scavenge gerotors.
Both plates sit between the feed and return gears.
The plates are separated by a spring washer that puts tension against each plate in opposite directions.
Thus sealing off the feed and scavenge sections.

Separator plate locations 13)

See also;
Inner Plate Dims

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

Inner plate (26463-77). Hole for the gearshaft is off center. Machined step is to locate the spring washer between the two plates. 14)

Inner separator plate installed position. (pump upside down) 15)

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.

Notice the difference of the cut out or recessed area of the inside diameter of the outer plates.
This is for the different style of seals. ¹⁶⁾
Either plate will fit 77-90 oil pumps with their respective seals.

Outer plate comparison 17)

77-82 oil pump outer separator plate top view 18)	77-82 oil pump outer separator plate bottom view 19)	Side view 20)

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

There were 2 different outer plate seals used on 77-85 oil pumps.

• (12036) was used on 77-82 models.
  • Sold for use with outer separator plate (26493-75)
• (12036A) was used on 83-85 models.
  • Sold for use with outer separator plate (26493-75A)
  • This seal was also used in 86-90 model oil pumps.

(12036) 77-82 Outer plate seal. 21)	(12036A) 83-85 Outer plate seal. 22)	Outer seal installed 23)

Spring washer (26461-77) was used on all 77-90 oil pumps.
It sits between the two separator plates and induces pressure against both plates and gerotor sets.
The spring washer is what creates the tension on the drive gear.

Spring washer (26461-77) 24)

The spring washer fits inside the inner plate. Fingers face toward the feed gears. 25)	Spring washer location as installed 26)

See also;
Gerotor Dims

• There were 2 different sets of gerotors used in Sportster oil pumps from 77-85.
  • 77-E83 (chamfered edges); Return set (26491-75), Feed set (26492-75).
    • Discontinued for production models by November of 1982. ²⁷⁾
    • Sold for 77-E83 oil pumps through 1984.
  • L83-85 (straight edges); Return set (26491-83), Feed set (26492-83).
    • Used on production models from L83-85.
    • The only year these were available for parts order as a set was 1985.
      (otherwise the only way to buy them was to buy the L83 oil pump assembly)
    • The original gerotors remained available for 77-82 oil pumps.
      (and the E83 pump)
    • The same return gears (26491-83) were used in 86-90 oil pumps.
      (however, the feed gears were changed)
    • So only the scavenge gears were available from 86-90.

• 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 ^{28) 29)}
  The new gerotors will retrofit to the 82 model pump body and cover. ³⁰⁾
• 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).

77-E83 gerotors. Chamfered outside gear edges. 31)	L83-85 gerotors. Straight cut outside gear edges. 32)

(26492-75) These can also be used on L83-85 oil pumps. ³³⁾

(26492-83) Straight cut feed gerotors.

(26491-75) Chamfered return gerotors These gerotors can also be used in L83-85 oil pumps. ³⁴⁾

(26491-83) Straight cut return gerotors.

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

Made by Circle Seal.
Manufacturer Part# P106-376.
HD Part# (26435-76A).
Patent #3626977.

Check valve (26435-76A) was an upgrade in L77 and used on all L77-85 models.
It has an arrow on the side for proper installation 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 ^{35) 36) 37)}
• 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.

26435-76A check valve 38)	With the O-ring removed, you can see the crimped 2-piece body design 39)

The check valve sits inside the bore in the pump body as shown. Installed position (R)40)

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 was used on L-77 to 90 models.

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)

Oil pressure switch (26554-77) 41)