What's this?

[AndyW]

Removed the trim panel held by two screws at the front of the tank....



Rubber bung pulls to reveal tube.... to?

 

[wessie]

is it for topping up coolant as per p214

https://manuals.bmw-motorrad.com/manuals/BA-Extern/IN/BA-INTERNET-COM/PDF/R_0M63_RM_0325_07.pdf

 

[AndyW]

Thanks I did suspect that but couldn't find the expansion tank.... and despite the drawing in the manual am still damned if I can see it!!!!