Using a 1 5/16" socket, loosen and remove the castle nut and the washer located behind it. Pro Tip - Pay close attention here. This tip will be mentioned more than once in this writeup! More than likely when you go to put torque to remove the nut, the axle/hub is going to spin...
Put the new C/S sprocket on, then the lock washer (either new or old). Note: When placing the new c/s sprocket on, you should have a 1/16" gap remaining for the lock-washer. Note about the Sprocket Direction If you didn't check when you took it off the face marked EXT (or...