The cap vents are actually inside the fuel cap asm! Open fuel cap and down at the hinge you will see 2 screws that hold the cap to the tank, in between the 2 screws you will see a little round hole with a little rubber round grommet, on the cap you will see a little stud or nipple in it with a hole , that mates to the grommet when the cap is closed. Remove the seat, find the vent tube, is on the lower left rear of tank, tube runs down and usually to in front of rear tire, pull the tube out and make sure it is not cloged, with fuel cap open, blow thru tube, you will know if it is clogged or not, if you have a Cal bike it will be the tube on the left, think it is marked with a blue dot, the back end goes to a canister under batt box. If that vent line is clear, you will need to remove fuel cap and disamble and follow the vent path to make sure it is clear. I think some one here posted pics, but was super easy, I did mine in about 20 mins! You will be amazed at just how small that vent path is in there and how easy it would be to get a clog.
04-3,200 miles bought July 2011 with 928 miles. Loaded with acessories to many to list here, see my albums for more details! I also make a custom tank bib specific for the 750 if anyone is interested, ck my albums for some pics.