I thought that also myself. All that grit and dirt and like you said, sand going down into the engine, bad juju! It looks like the top part of the tube is not just a tube it's part of the plastic piece that sits underneath the outside panel where the key goes to unlock the seat. That upper tube is not going to move unless you do some major work. Also the lower part of the tube has just a bolt in it. Just maybe by removing that bolt that lower tube will slide up high enough to come out of where it is given us access to change the O-ring It seems as though that the engine crank case is pressurized(may be too much causing it to blow past that only in the filler neck. If you notice when you takeoff the left hand cover for the airbox you'll find oil inside there. I'm not sure why there was a puddle in there when I removed it. I only have 4000 miles on the bike. I couldn't imagine if I have more than 20,000. I'd say there was 2 tablespoons. I'm guessing the crank case gases are going into the air box through a tube that's in there and that's why it has oil in it. So if you have an oil leak from your airbox, you'll know what's going on.