I bought a gw2015. Did not ride much, but I have noticed a weird thing. Hard to explain. The fuel tank lid has some empty space inside (like a rim) which holds water, so rain water or any water from washing will stand under the lid and will eventually go inside the tank and mix with fuel. the lid is not sealed.
I am not sure if someone noticed that and does Suzuki know this?
Thanks for that, and I'm glad you found the problem. You may want to check for a drainage hole in the inside flange/rim below the fuel cap, where rain or over spilled fuel could settle, and drain out. If you find it, maybe the hole is clogged up and won't allow drainage. My bike definitely has a drain hole, so I know Suzuki has thought it a potential problem. But I honestly have NO idea where it drains to.., maybe back into the Tank. Wouldn't that be a SNAF idea.