well the other day i got the naked 900 running and ridable. put some fuel in it so i could ride down to the gas station. filled her up w/ that pricey petrol. rode about 5 miles and went home. shut her off in the garage and fuel dumped out of the vent tube on the bottom of the tank. did a search on any fixes and wasnt happy w/ spending money to get a new tank since i just fixed mine up. i went to the local shop and got a $16 dirtbike/ atv fuel cap vent. i then drilled the hole on one of the fake bolts out from the bottom and then drilled a hole in the top of the tank. works great. its a no leak check valve vent so no gas can leak out.
sorry bout the fuzzy pics, crappy camera

 

Did you use a sealant around the tube. My original vent tube is plugged also.