The stock brake pads of the F650GS tend to make a terrible squealing noise, especially when being wet. Replacing them with aftermarket pads may help.
Please be sure to run new brake pads in smoothly. Don't brake hard during the first 100-200 km. This is because the material mix of the pads has to be kinda re-arranged under heat, and the pads have to get used to wear and tear marks of the rotor. After those 100-200 km everything should be fine.
One of the manufacturers of AM brake pads is EBC. Currently no experiences, will follow later.
German importer Ingo Weber
M & P