hey not the top tube , the 2 middle tubes .
Originally Posted by 2door
Don't cut the top tube. If it is removed there will be no frame strength. Yes, there are 'step-through' frames, women's bikes, but their frame design is different that a man's bike and the structural design doesn't require the top tube like your bike has.
View the bike from the side and try to picture the forces applied to the frame when you're riding it. Your weight plus the shock of bumps will put all the force on the down tube where it attaches to the bottom bracket. The frame will fold up like a lawn chair without some structural support from the stem to the seat tube.
Find another way to mount that tank or find another tank or bike.