Who does not know the problem with the oil leak, oil mist
on the rocker boxes (valve covers) screw connections?
Once the rocker box screws have been opened
it was for the Bonded Seal discs, after that they are no longer tight.
Therefore, remember this every time you open the screws, due to the exchange of the seals
or exchange for other Rockeboxes, order the rubberized discs at the same time
otherwise you'll have to do it all over again weeks later when the engine is pretty smeared with oil.
The cross-section of the image shows why this is the case
And why these parts cost more than a normal washer is hopefully clear to you.
Thanks to my good contacts in the industry, I found the manufacturer and directly from the factory
I ordered a not insignificant amount, which I can offer at a much more interesting price.
Price is unit price, so for 2 rocker boxes you need a total of 8 pieces
For reference
Original part number = 6589A
former spare part number = 6589
For all EVO1340
Sportster 1986-2020
TwinCam 2000-2017