Good evening, I'm a RVF prepare for the race, I have watched a lot of photo rvf for the race, I have noticed that the RVF were tank of gasoline nc 30. Why this change?

I guess the NC30 tank is easier to find and cheaper too; the two tanks are interchangeable as the air scoops on the RVF400 are removable and since they're mostly for 'show' they're not really needed on either bike.