I'm going to assume that my '95 900ss is the same as yours. Having said that - the collar is a b!tch to remove. I have used a 1"x1"x12" piece of wood and leverage it out GENTLY by moving the piece of wood around and give it a tap with the palm of your hand - no hammers here.
There's a O-ring that goes around the collar that fits inside a groove and it's tight. It sounds like you have completely removed the grub screws but if not, you should do that.
When you put it back together, you'll have fun keeping the rubber seal that fits around the edge of the collar and the tank in place....
