Hi,
I just built my new DB01R buggy and for the first time i built dampers without a cap (diaphragma) at the top of the cylinder.

The manual says you have to fill oil until 1mm to the top. I rated that or is there a simple way to measure that? When taking too much oil it seems the piston isnīt able to fully compensate and if you fill in not enough and fully press the piston it sounds as if there are air bubbles inside.
Did i build something wrong? Any help would be much appreciated. I have been building many many dampers over the years but never without a cap.
Thanks in advance!