It does not have to be empty.It has a valve built in.At least on my 05 it does.
When I remove the line, I don't lose but a drop or two. It is easier to do with the tank as empty as possible.The tank is a lot lighter. I put a towel around the front of the tank to keep it from getting scratched up on the frame,handlebar risers,and trees. Then remove the rear bolt, and then the two front ones. Carefully lift the rear up enough to reach under the tank and disconnect the fuel line and the drain or vent hose that connects underneath.The fuel line has a small hose clamp, I use a long straight screw driver.
Then if I remember correctly I lift the front and slide it back a little.
Then it should come right off.
It's actually pretty straight forward.
Once you remove the top of the air cleaner,you can see down the throttle bodies.You can turn the throttle to open them, then slide something long and thin in there to hold em open.Preferably something plastic so you don't damage the butterflies.
I use long q-tips and carburetor cleaner to clean them.Just swab the blades and the throat of each throttle bore.If they are dirty,they will be pretty black.When clean, they are all shiny.
This whole job takes about an hour.
'14 Ness XC