Hey guys, being new to this motorcycling thing I got two questions...
--Question 1--
So I fill up at the gas station about every week. When you look in you can see the gas rise up to the bend in a metal line to where there's a screw which is about 2.5" toward the ground under the gas cap. If I fill any higher than that, then gas starts to leak out of here:
So i traced one of the lines back up to the gas tank and the other just gets lost in oblivion. The one that leads up to the gas tank is shown as the third (rightmost) line in the pictures below. The gas tank has a sticker which states:
Battery(?) | Backflow | Dreinage

The line is hooked up to the "dreinage" spout from the gas tank. When I fill up a "full tank" from the gas light, it's 2.1 gallons. When I fill up from completely empty, it's about 3 gallons. I know the Supersport is 4.1 gallons so where the heck did my other gallon go if it's just going to leak out while I ride?
Someone has told me that it's probably a hole in the line that goes up into the tank. I was wondering if it's advisable to just plug the dreinage line since it doesnt rain down where I live, I never keep it in the rain, and i dont want gas leaking out when the bike gets dumped (happened before).
--Question 2--
I run Pirelli Diablos on my 91 900SS. What size should I go with if I choose to get a new set of tires and what brand/model of tire should I get next? I do A LOT of commuting with the Duc so my priorities in order are: treadlife, cheap price, handling, brandname, looks. Should I get the Dunlops and wear down the triangulated profile or should I go with some Continentals because they're cheap and claim to have thicker tread and last longer. I just don't want the tires to be bordering the "i'm gonna die if i take it up to the canyons" status because the Diablos have served me well.
Much thanks! I'm in SoCal if anybody has any hookups to reference.