1. Remove the radiator cap.
2. Disconnect the siphon hose at reserve tank and drain.
3. Flush the coolant reserve tank with clean water.
4. Reconnect the coolant reserve tank hose.
5. Remove the coolant drain bolt from the water pump cover and drain coolant.
6. Flush the cooling system with water through the radiator fill neck until the water coming from the drain bolt hole is clear. NOTE: If you are going to switch to Engine Ice then flush with a mix of 50/50 white vinegar and water, then flush with water to eliminate the 50/50 vinegar/water mix.
7. Install the drain bolt...don't over tighten.
8. Refill cooling system with coolant through the radiator fill neck. Do not install the radiator cap at this point.
9. Lean the bike from side to side about 20 degrees to remove air trapped in the cooling system. Fill as necessary and repeat this step until the coolant level in the radiator stops dropping.
10. Install the radiator cap.
11. Fill the coolant reserve tank to the minimum mark. Do not install the cap at this time.
12. Bleed air from the system as follows:
a. Start the motor and let run for 2-3 minutes
b. Snap the throttle three or four times to bleed air from the cooling system.
c. With the bike level check and engine running check the coolant level in the coolant reserve tank NOTE: I did not say the radiators as that would be dangerously foolish as the coolant is now hot. Never remove the radiator cap when the coolant is hot.
d. Turn the engine off and add coolant to the reserve tank to bring the level to between the minimum and maximum level marks.
13. Check the drain bolt and hoses for leaks.
That's pretty much it for changing the coolant on a 250X.
Good luck!
Ken