If it's contaminated or your changing oil types, you'll need to remove all the oil in the rotary chamber and tank.
The best way to remove it all is to pull a vacuum from the hose that runs to the top of the tank from the rotary chamber. This will pull all the oil down into the rotary chamber and out the vent line.
Make sure you have the oil cap off.........:cheers:
I changed mine yesterday (because I was swithching brands). I bought an electric oil change pump that hooks up to the battery for $25. They are typically used for changing oil in boats ( I was buying to use for my boat anyway), you just stick a plastic tube down the dip stick tube on the boat and pump the oil out. I used it on my '97 GSX, stuck the tube down the return line (the one snipe indicates that goes to the top of the tank). It worked great.
Here is a link to one online, I have a Cabela's near me that socked it.