Rode 5000 miles to Alaska this summer; started with 4k on the bike, with no "stalling" problems. Rode 3000 miles with a lot of cold rain - a third to half of the time. At 7k, pulling off the highway into a service station, the bike stalled; dry day, about 60 deg F, one gal left in tank. Giant sucking sound when I opened the gas filler. This is the only stall I have had but the tank always has a vacuum now when I fill up (or check to see how it's doing).
Previous bike, KTM950Adv, had the "cannister" problem, which removing the cannister did not solve. It's problem was the venting in the filler caps didn't work right - a "flapendectomy" fixed it.
There definitely should not be a vacuum when I open the filler cap. I'm wondering if the F800GS filler cap has similar venting? I cannot check mine right now because the bike is in transit from Alaska.
Ride report: www.nibbelink.net/html/alaska09.html