Measure from the risers to the curve in the bars to see if they are offset. The bars are installed by the dealer at setup time and they usuall just do it by eyeball. If they are centered in the risers, measure from the ends of te bars to the center of the cap on the fork stem to make sure the handlebars anre not twisted slightly. If this is also OK, remove the seat, loosen the bolt holding the tank in place and make sure the tank is centered.
Oh, and like he said, lift straight up on the front of the tank. If you can lift it, it's not installed onto the rubber guides correctly.
