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 1)

The inner plate part number (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. 2)

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. ³⁾
Either plate will fit 77-90 oil pumps with their respective seals.

Outer plate comparison 4)

83-90 oil pump outer separator plate top view 5)	83-90 oil pump outer separator plate bottom view 6)	Side view 7)