The drive sprocket on an Echo chain saw is a part of the clutch assembly and allows the clutch to spin the chain. The chain rides along the notches of the sprocket at incredibly high speeds, sometimes over 10,000 rpm. For this reason, a lot friction tends to wear the sprockets down and when your sprocket is worn out, you may notice loud crunching or whining sounds from your clutch. Replacing the drive sprocket will help reduce wear and tear on the other clutch parts.
Pry the clutch cover off. Lift the guide bar up and pull the guide bar and chain from their seat on the drive sprocket. Remove them from the drive sprocket if you can. If you can’t, leave them in place until you remove the clutch drum.
Pry loose the rubber boot that is attached to the spark plug, near the rear handle. Unscrew the spark plug with the socket wrench and remove from its seat on the engine.
Stuff the rubber piston stop tool in where the spark plug was. Turn the clutch by hand until the piston stop tool stops the piston from moving in the cylinder.
Loosen the clutch drum with the Allen wrench. Pull the clutch drum from the crankshaft. Pry the drive sprocket and needle bearing from the clutch drum. Discard the old drive sprocket.
Grease the needle bearing using about a fingertip of grease. Spread the grease around the inside and outside of each bearing. Set the needle bearing into the replacement sprocket.
Push the drive sprocket and needle bearing into the clutch drum. Slide them all back onto the crankshaft. Lock them in place by tightening the bolt using the Allen wrench. Set the chain and guide bar in place on the clutch. Tighten the clutch cover with the wrench.