Are you sure? I would also look at the Cam cover Gasket to on the side right next to the throttle bodies to make sure it is not leaking and seeping down behind and under the oil tank. Not that yours is not leaking but I took mine off three times before I caught on
If your sure it is the tank try to loosen the two top bolts and wiggle it a wee but and then tighten them down it might re-seat the O-rings. Just loosen them up two or three turns should be enough to wiggle it. Other then that your will have to pull the throttle bodies off the engine. You can leave the throttle cables on the unit and just hang it from the handle bars.You can leave the tank on but you will have to take the fuel line off the tank just lay a towel up there to catch what fuel comes out of the line. the tank had a stop check valve in it so it will not drain.
This is why I would first check the cam over gasket and try to re-settle the tank on the O-rungs first. Its easier and takes little time. There is two O-rigs under the tank to the block. On older bikes the tolerance on the fit were looser which made them a little persnickety.