Pressure won't matter in where the coolant is. Normal would be for the level in the overflow to be more when warm as the coolant expands due to heat. It would then slowly go down as the bike cools off. Be sure you are checking under the same conditions and that empty really is empty. I know on one of my Busas I had to take the side fairing off to see the coolant level. It looked empty no matter how hard I tried to see it with a flashlight, no flashlight, etc. It wasn't empty when cold, was normal.