Oil Filler Cap - how to take it apart
Lay the cap upside down on a good support
Press down on the measurement rod and twist until the cut-outs are matching the latches, let go
The spring will move the stem up and the pieces come apart
Now you can easily change the gasket, replace the spring if needed and verify the quality of the tabs and the rivets of the rod.
Revert the process for assembly
Hartmut