This primary cover swap was done by XLForum member, 85IRONDIRT, on a 1985 XLH 1000. ¹⁾

In 1977, Sportsters got new cases to accommodate the left side shifter.
And through all the engine changes including case changes and the swap to the Evo cases in 86, the primary cover mounting holes on the cases stayed the same.
The OEM primary cover gasket (34955-75) will fit 1977-1990 Sportsters as per the parts catalogs.

However the 86-90 primary cover is more shallow than the L84-85 cover.
But it will bolt up to a L84-85 case and clear everything internally running the L84-85 clutch which uses the spring washer for the pressure plate.

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Considerations:

• You will have to use all the hardware from an 86-90 model due to the cover not being as deep.
• The lowest front stud will be too long.
• The stud for the footpeg sticks out of the cover by about 3 inches.
• The shifter shaft will also be about 3 inches too long so you'll need the 86-90 shifter shaft (34628-86).
• The shorter 86-90 perimeter bolts will have to be used.

Parts:

• Primary Cover (25430-86 or -86A) loaded.
• Primary Cover Screws (3481) 1/4“ x 20 x 1-1/2” Socket Head Screw (10)
• Primary Cover Gasket (34955-75)
• Shifter Shaft (34628-86)
• Left Footrest Stud (24752-86) 1/2“ x 4-1/8”