ECHO CS3500 CS3700 CS4400 CS5100 Oil Drive Pump & Worm Gear

Oil drive pump and worm gear fits Echo CS3500, CS3700, CS4400 and CS5100 chainsaws. Supplied as a matched set — the oil pump body and the worm gear that drives it are replaced together, which is the recommended approach when oil starvation is diagnosed on these saws. The worm gear sits on the crankshaft and meshes with the pump rotor to deliver a continuous flow of bar and chain oil to the guide bar groove during cutting. Either component failing in isolation produces the same symptom a dry bar despite a full oil tank — so replacing both as a set eliminates the need to diagnose which part has failed and prevents a worn gear from accelerating wear on a new pump body. Fitting a replacement set restores full chain lubrication and protects the guide bar and cutting chain from heat damage.

Fits the following Echo models:

• Echo CS3500
• Echo CS3700
• Echo CS4400
• Echo CS5100