Is the gas cap supposed to vent?

My GPZ 1100 does the same thing. Gas also comes out of it when I use the kickstand which is a major pain. The gas tank actually has perminent gas stain from leaking out the kickstand side. Is this normal? The tank doesnt have to be too full either, just random sloshing around makes it happen too.

Sounds like the gas tank lid seal is shot. I'd recommend getting a replacement seal. Call Z1 Enterprises to see if they can hook you up.