Fuel cap issues

[kendunn]

Of all things to break first on my new to me 2002 EC300 was the gas cap. Cruising down a backroad on the way to a local trail and it started acting like it was running out of gas and died. Pulled the fuel line off the carb thinking my filter was stopped up or something and heard it start sucking air in. Hmmmmm, I thought, stopped up vent tube, but no. Took the fuel cap off and the rubber was collapsed on the bottom of the cap. Blew on the top of the cap and it popped back open only to close up again about an hour into the ride. Is this a common problem or is it just my good luck? I figured I could just cut a bigger vent hole in the rubber or something. Will this solve the problem?
Thanks
Kenny