Vacuum in the tank - pinched breather hose

The red area indicates where the hose was and where on of the rubber grommets of the seats also sets.

I noticed a strange thing on the bike when opening the gas cap. There seemed to be a somewhat strong vacuum in the gas tank and I had to really pull to get the gas cap off. I didn't pay much attention to it at first, but after the 2040 km trip I really started to wonder. None of my other bikes acted like this so something probably wasn't right.

I posted on a 690 thread on a bike forum and immediately got a reply that vacuum isn't normal and I probably had a clogged/kinked/pinched breather hose. Sure enough after removing the seat I found that the hose had been pinched by the seat and I had been practically sitting on the breather hose.

Problem was easily solved by moving the hose half an inch inwards so it would not be left under the seat grommet. I still need to pay attention when resetting the seat. It did leave me wondering if the hose really should be routed like this.