i have a 06 zx10 and i have just recently discovered the same problem. just yesterday i pulled the tank off and checked all my lines and the tank itself no signs of leaks anywhere. do you have a power commander?
My bike had no smell. I removed tank, removed injector rails and reinstalled and added new map. now it smells like gas when running, and after running. faint vapor smell. any place that is a usual suspect???