Diagnosis
The most common cause of a loud grinding noise and burning plastic smell on a Greenworks 40V chainsaw is the chain being installed backwards, so its cutting teeth are facing the wrong direction. This causes the dull drive links to rub violently against the bar rails and the clutch sprocket, generating excessive friction, heat, and that distinctive acrid smell. A second possibility is that the chain brake mechanism is partially engaged, creating drag.
How to Fix It
- Disconnect the battery.
- Loosen the bar tensioning knob and remove the side panel to access the bar and chain.
- Lay the bar and chain flat. Identify the cutting teeth; they should be facing forward along the top of the bar.
- Reinstall the chain onto the bar so the sharp, angled cutting edges on the top of the bar are pointing toward the bar tip (the direction of rotation when cutting).
- Reassemble, ensuring the chain tension is correct—it should snap back lightly when pulled from the bar.
If That Didn't Work
Inspect the chain brake. Ensure the front hand guard is completely forward and not resting against the clutch cover, which would apply drag. Also check for severe bar rail wear or a damaged drive sprocket caused by the backwards chain, as these may need replacement. Finally, verify the chain is adequately lubricated; a dry chain can also overheat and bind.
Heads Up
Running a chainsaw with a backwards chain quickly destroys the bar rails and can permanently damage the motor or drive system due to overload. Always visually confirm the cutting teeth face forward along the top edge of the bar after any maintenance.