If it is the exhaust flap sticking (and it certainly sounds like it is), lubing it with WD40 will only last so long until the heat of the exhaust burns it off, you need something like nickelslip or coppaslip in there to survive the heat.
Take the cables off the drive servo and make sure the flap is open (it should spring open but if it is suffering lack of lubrication it may not do this without external force)
The flap serves only to reduce noise, BMW supplied and fitted aftermarket headers do not use it so there is no problem removing it or disabling it in situ.
Removing the flap ( I have) does actually generate a fault code at service time but the fault can not be cleared as there is no valve flap for the diagnostic to find
Not that anyone should be concerned about this fault as the bike is better for it IMO

I'd just ignore it, they do seize up occasionally. I had to be told mine had seized as I had not noticed!
As mentioned the WD40 will stop it only briefly, don't worry about it at all, just have a great time.
I do have a full OEM system sat in my garage if you want a cheap slightly used one when you get back.
only just read this thread as i have just encountered the squeaky exhaust flap whilst in southern spain....i must admit that it made no difference to the bikes performance and i rode it home and then lubricated it.....however..... i read the post from edwgordon and was surprised (or not..) by the knobs on here who simply take the piss.....probably experienced adventure travellers who do a whopping 850 miles a year on their spotless machines..... This guy was asking for help / advice as he was unsure and a little worried about a noise on his GS, he may not be a mechanically minded chap and be unsure whether to ride on or not..... bear in mind he could be a doctor or dentist which none of us know fuck all about and therefore attend them for advice.... It pisses me off that knobs take the piss when a guy clearly needs some sensible advice and help whilst on his holiday.....in other words..if ya got fuck all to say..dont say it.... Rant over... and in future help ya fellow bikers...
Buy some tools if your not carrying any and remove it free it off lube it up and refit a 10 minute job or just ignore it On the last trip we did we had the charging system on a blackbird spread all over the floor adds to the fun its the unpredictable things that make bike touring fun
only just read this thread as i have just encountered the squeaky exhaust flap whilst in southern spain....i must admit that it made no difference to the bikes performance and i rode it home and then lubricated it.....however..... i read the post from edwgordon and was surprised (or not..) by the knobs on here who simply take the piss.....probably experienced adventure travellers who do a whopping 850 miles a year on their spotless machines..... This guy was asking for help / advice as he was unsure and a little worried about a noise on his GS, he may not be a mechanically minded chap and be unsure whether to ride on or not..... bear in mind he could be a doctor or dentist which none of us know fuck all about and therefore attend them for advice.... It pisses me off that knobs take the piss when a guy clearly needs some sensible advice and help whilst on his holiday.....in other words..if ya got fuck all to say..dont say it.... Rant over... and in future help ya fellow bikers...




only just read this thread as i have just encountered the squeaky exhaust flap whilst in southern spain....i must admit that it made no difference to the bikes performance and i rode it home and then lubricated it.....however..... i read the post from edwgordon and was surprised (or not..) by the knobs on here who simply take the piss.....probably experienced adventure travellers who do a whopping 850 miles a year on their spotless machines..... This guy was asking for help / advice as he was unsure and a little worried about a noise on his GS, he may not be a mechanically minded chap and be unsure whether to ride on or not..... bear in mind he could be a doctor or dentist which none of us know fuck all about and therefore attend them for advice.... It pisses me off that knobs take the piss when a guy clearly needs some sensible advice and help whilst on his holiday.....in other words..if ya got fuck all to say..dont say it.... Rant over... and in future help ya fellow bikers...