Fx maverick leak

[Jtlies1]

Does anyone know exactly where the fill port piston is? I have a significant leak and fx usa told me to replace oring #5107 located there...but i cannot find that piston anywhere.

 

[nervoustrig]

Piston = check valve in the Foster fitting.

Typical example:

Note the white (polyurethane) O-ring on the silver part.