The chainsaw's chain brake, when engaged, automatically stops the clutch from rotating. This safety feature should be present on every chainsaw according to OSHA regulations. The brake is activated by a highly tensioned spring under a cover plate. For safety reasons, eye protection should always be worn during the spring removal. Whether your chain brake won’t engage or you can’t free a locked spring, you will need to remove a number of parts, which can be difficult to reassemble.
Disengage the chain brake (if you can) and loosen the bar tensioner screw to release chain tension. Remove the bar cover’s bolts with the wrench. Reengage the chain brake by pushing the black handle forward.
Unscrew the half-wrap or full-wrap handle’s retaining screws. Remove the handle from the engine.
Slide the rubber wire off the spark plug. Remove the spark plug from the engine. Insert the piston stop tool into the empty spark plug hole. Remove the starter cover and turn the flywheel by hand until the piston contacts the stop tool.
Remove the clutch drum and drive sprocket with the clutch removal tool. Remove the oiler’s cover plate mounting screw. Pull off the oiler cover. Remove the four screws holding the cover over the oil pump with the Allen wrench.
Press the flat-bladed tip of the screwdriver underneath the back end of the spring. Carefully release the spring’s tension from its hook. Disconnect the spring from the lever. Do not attempt this step without wearing protective eyeware.
Ease the brake band off its seat on the crankcase, which is usually located behind the clutch. Disconnect it from the lever as well.
Remove the E-clip from the pivot pin. Pull off the lever and hand guard from the pivot pin. Unlatch the spring from its second hook and remove it and the lever.
Check all of the parts for damage. Clean them with an engine cleaning solution. Replace any worn-out or damaged parts.
Reassemble the brake in reverse order. Use new E-clips and make sure the lever is installed correctly before starting the chainsaw. Ensure the brake works at full speed before cutting with the chainsaw.