I think the only way to deal with a problem like that (I'm assuming you know that it's a problem...your bike you know what's normal) is to just take the tank off and do a little recon. You'll probably notice something out of place and then you can come back and see what people think. If you know the problem is in the tank then go in there and grab it by the balls. 
I'm no expert but taking the tank off was not a problem. I missed the drain the first time because I was trying to figure out which hose it was... Turns out it was painted the same color as the bike and it's a little plug...and it was really in there good. I didn't have any problems with any of the hoses releasing gas when they were disconnected.
If you have problems I'm sure there is plenty of information to be had from a forum search.
I'm no expert but taking the tank off was not a problem. I missed the drain the first time because I was trying to figure out which hose it was... Turns out it was painted the same color as the bike and it's a little plug...and it was really in there good. I didn't have any problems with any of the hoses releasing gas when they were disconnected.
If you have problems I'm sure there is plenty of information to be had from a forum search.
