I only have the coolant capacities listed for 2003. Yours should be about the same though since it really is the same machine. If yours has a radiator near the chaincase, then your coolant capacity may be slightly higher.
Capacity is listed at 4.7 L and mixing ratio is listed as 3:2, so dump out and replace 1.88 L of coolant with water (assuming that it is currently 100%).
If you drain it too far, you may need to bleed it. Bleed procedure is to lift the rear end up (not higher than the coolant bottle), remove drain bolt on cross-tube, fill until there is no air up to cold level. Replace drain bolt and cover bottle, run 3-5 minutes and bleed again. Repeat until there is no more air. If it gets hot while doing this, don't remove the bleed bolt or open the bottle -- let it cool down first.
I am not aware of any drains on the system, you may have to just remove a hose. If you are very patient, you can lift the front end up and drain it through the bleed hole in the cross tube. This will probably be the easiest way anyways, since it will drain in a controlled manner. You can add a measured amount of water as it is draining and close the drain bolt when all the water has been added. This approach eliminates the need to bleed the system.
