Doing your own maintenance on your chainsaw is a great way to save money. Replacing the sprocket on an Echo chainsaw is a fairly easy proposition.
Things You'll Need
Socket and wrench
Use your scrench to remove the two bar nuts on the clutch cover. Take the cover off as well as the bar and chain.
Use an 8 millimeter socket or special clutch removal tool to remove the clutch. This will be a left-hand thread, so you will turn to the right to loosen.
Remove the top cover and he spark plug from the saw. Stuff about four inches of nylon cord into the cylinder through the spark plug hole to keep the piston from moving while loosening the sprocket nut.
Remove the entire clutch assembly. The sprocket is attached to the clutch drum, so the entire part will need to be replaced. Check your owner's manual or with your dealer for the correct part number for your model.
Reverse steps 1-4 to put the saw back together.
Be careful that the nylon string does not make it's way out the exhaust. This will lead to small bits of string that need cleaned out of the cylinder.
Wear gloves when handling the chain. It is sharp and can cut, even when it's not moving.