Leaky gas cap

Does anyone else have a problem with the gas cap leaking?

I think maybe its a california model problem? from what I can tell its coming from the vent hole under the cap. I sit on my bike when I fuel so its level and I always stop below the filler neck like the manual says and with out fail I always get some gas running down the outside of the tank after a few turns until its around 1/2 - 3/4 full.