I've got a 07 Z1k with 300km on it. It was fairly chilly today at 5C, but my bike was dirty so I started washing it with warm water of about 40C.
As I started working on the fuel tank, I was hearing that funny air leak sound, just like right after you put in coffee or hot water and close that thermos vacuum container. Sure enough, I smelled gasoline from there.
I know that the air inside of tank gotta go somewhere, but I thought tank cap was air-tight. I've never had anything like this with my previous bikes. Do you think the seal on the cap is defective?