I ran into this problem on my bike a couple of weeks ago. I took an 18 gauge(might have been 20) piece of solid copper wire and fed it down through the vent in the gas tank. Had to go slow and feed it with a pair of duck bill pliers just a half an inch at a time once I got to the bends, but it finally came out the tube at the bottom of the tank. I stuck a paper towel under there while I was feeding the wire thru and all I got were a few paint chip looking particles. Didn't look like enough to clog up the vent line, but I haven't had any gas tank pressure problems since then.
You should be able to find small spools of the copper wire I used at your local auto parts store. Stripping off the insulation seem to ease the trouble to feed it through. Using some wire feeding snot would probably be an even better way to do it, but I was too lazy to make the trip to Home Depot or Lowes.
Of course if my bike was still under warranty, I'd have taken it to the dealer.
