Stihl 020AV Chain Brake Repair (Step-by-Step)
To repair an 020 AV chain brake safely, identify the exact saw version first; clean and inspect its brake band and linkage; replace damaged parts only with serial-number-matched components. Never release a loaded brake spring by hand. Reassemble with the specified compressor and manual, then confirm positive engagement and release before the saw returns to service.
A brake fault can stop a weekend job, but guessing at parts can make the repair more costly. Reusing sound, compatible parts and replacing only what has failed can be a practical way to extend the life of a legacy saw. Dispose of drained fuel and oily waste according to local rules; do not keep using a saw with a faulty brake to avoid repair costs.
Identify the brake and prepare the saw
The first step is to confirm that your exact 020 AV has a chain brake and to find the correct service information. Versions and parts may differ, so do not assume that another 020 AV’s repair steps or parts fit yours. Treat the brake spring as hazardous until you know how its assembly is safely controlled.
Look up the saw’s serial number in the appropriate parts information and service manual. Check that the diagram matches the brake cover and hand guard on your saw. If the saw has no brake, do not try to add or adapt one using parts selected by model name alone.
Before work:
- Stop the engine, let it cool, and disconnect the spark-plug lead.
- Wear eye protection and cut-resistant gloves.
- If tilting the saw could spill fuel, drain it as directed in the manual.
- Brush away dirt around the clutch cover before loosening it.
- Photograph the hand guard, linkage, and cover before removal.
- Gather the specified replacement parts and the brake-spring compressor required by the service procedure.
If the brake is engaged, use the manual’s release procedure before removing the cover. Do not force the cover against the clutch drum or brake band. If you cannot identify the correct procedure, tool, or parts, stop and have a qualified chainsaw technician handle the brake assembly.
Step 1: Remove the cover without forcing it
The clutch cover is the side cover that holds the brake components around the clutch area. Remove it only when the brake is in the position required by the manual. A brake spring can hold strong tension, and an uncontrolled release can injure your hands or eyes.
- Keep the engine off and the spark-plug lead disconnected.
- Follow the manual’s instruction to release the brake, if required for cover removal.
- Loosen the cover fasteners and lift the cover away without prying.
- If it will not come free, stop. Check the brake position and manual; do not lever it off.
- Place the cover on a stable work surface. Keep fingers clear of the spring and linkage.
Do not take the spring out just to “see what is wrong.” The spring must be controlled with the correct compressor and handled in the documented sequence. If your manual does not describe the procedure or you do not have the tool, leave the spring assembly intact and refer that part of the job to a technician.
Step 2: Inspect the brake and find the fault
A brake band is the metal strip that tightens around the clutch drum to stop the chain. Inspect it, its anchor points, the linkage, and the hand guard for visible damage or obstruction. A sawdust-packed cover may need cleaning, but a cracked, distorted, badly worn, or contaminated part needs proper repair or replacement.
With the engine off, check for:
- Cracks, deformation, corrosion, or unusual wear on the band, cover, hand guard, and linkage.
- Heat discoloration or damage to the brake band.
- Oil, grease, or packed sawdust on brake friction surfaces.
- Loose, damaged, or missing fasteners and damaged anchor points.
- A hand guard or linkage that sticks, binds, or fails to move as described in the manual.
Clean packed debris from the cover pocket. Keep friction surfaces dry; do not oil or grease the brake band or drum. Do not bend the linkage or reshape the band to change how the brake engages. Replace damaged or heat-discolored parts with components confirmed for the serial-numbered version.
Use this table to choose the next step:
| Finding | Action |
|---|---|
| Debris in the cover pocket; no visible damage | Clean the pocket, then inspect and test by the manual |
| Oil or grease on brake friction surfaces | Find and address the contamination; do not return the saw to service until the brake works as specified |
| Cracked, distorted, badly worn, or heat-discolored brake part | Replace with the correct compatible part |
| Broken or loose linkage, hand guard, or anchor | Repair or replace according to the service information |
| Spring needs removal, or cover will not come off freely | Stop unless you have the specified tool and procedure |
Step 3: Repair or replace the failed parts
A repair is not complete when a part merely looks clean. The spring, band, linkage, and cover must be in the documented positions and work as a system. Use the matching parts diagram to confirm orientation and part numbers; do not substitute a similar-looking component without verifying compatibility.
If the fault is loose debris, clean the cover pocket and inspect the brake again. If a part is damaged or contaminated beyond safe service, fit the specified replacement. When spring removal is required, use the correct brake-spring compressor and follow the exact service procedure. Never pry out or reinstall the spring with improvised tools.
Before closing the cover, check that:
- The replacement parts match the saw’s serial-numbered parts information.
- The band, linkage, and spring are oriented as shown in the service instructions.
- Friction surfaces are clean and dry.
- The clutch cover, hand guard, and fasteners are not damaged.
If you lack the proper compressor, service instructions, or verified parts, stop at this point. A dealer or qualified chainsaw technician may cost more up front, but an uncontrolled spring or mismatched brake part can cause injury or leave the saw unsafe.
Step 4: Reassemble and test the brake
Reassembly means restoring every brake component to its specified position and tightening the cover fasteners to the manual’s torque. There is no safe universal torque or spring sequence for every 020 AV version. After assembly, check positive brake action before starting the engine, then follow the manual’s running test.
- Install the spring, band, and linkage in the documented orientation, using the specified tool and sequence.
- Fit the clutch cover without forcing it into place.
- Tighten fasteners to the exact torque in the correct service information; do not guess.
- With the engine off, move the hand guard as directed. Confirm that the brake engages and releases positively.
- Check the chain tension and make sure the chain is correctly installed.
- Secure the saw, keep the chain clear of people and materials, and start it outdoors using the manual’s procedure.
- At idle, confirm the chain is stationary. Perform only the brake function check specified in the manual.
Never rev the engine with the brake engaged. Do not test the brake by making a cut. Stop the engine at once if the chain creeps at idle, the brake binds, you hear abnormal noise, or the action feels uncertain. Do not return the saw to cutting until it passes the documented test.
A chain brake does not prevent every kickback injury. Follow applicable OSHA requirements and ANSI Z133 work practices for the task, and use safe work positioning. If the manual’s test is unclear or the brake does not act positively, have a qualified technician inspect it.
Repair scenarios that help guide the decision
The examples below are diagnostic scenarios, not reports of a specific customer repair. They show how I separate a cleaning job from a spring or parts repair without guessing from the model name.
| Scenario | What the inspection shows | Safe next step |
|---|---|---|
| Hand guard feels stuck | Sawdust is packed into the cover pocket; no visible damage | Clean and inspect. Reassemble and test by the manual |
| Brake action feels weak or uneven | Band is heat-discolored or visibly worn | Replace the affected compatible parts; do not reshape the band |
| Cover will not lift off | Brake may still be engaged or caught against the drum | Stop and follow the version-specific release procedure |
| Saw starts, but chain moves at idle | Brake repair does not explain the chain movement by itself | Stop the saw. Check the correct idle specification with suitable equipment and have the brake assessed before use |
In particular, do not change idle speed to hide a brake fault. Set idle and maximum speed only to the specification for the exact saw version, using suitable test equipment. Fuel mix is also not a brake adjustment: use a 50:1 mix only if the oil label and the applicable saw manual permit it; otherwise follow their fuel instructions.
Maintain the brake and store the saw safely
Routine care helps you spot brake damage before the next job. Clean the cover pocket at service intervals and whenever you find packed debris, oil, or unusual wear. Keep friction surfaces dry, and check related parts such as the chain catcher, hand guard, clutch drum, sprocket, and chain tension.
Replace worn or damaged parts with compatible components. Do not bend the linkage or alter the band to “adjust” engagement. Record the part numbers installed and whether the manual-prescribed functional check passed. Recheck the brake before each return to service and after an impact or cover removal.
Before storage, clean and dry the saw. Protect exposed metal from corrosion without getting oil on brake friction parts. Store fuel as directed by the fuel and oil manufacturers and the saw manual; stale fuel can complicate starting and post-repair checks. A starting problem does not prove that the brake repair failed, but it also does not make a faulty brake safe.
Frequently asked questions
Can I repair the chain brake without a spring compressor?
You can clean and inspect accessible areas, but do not remove or reinstall a tensioned spring without the specified compressor and service procedure.
Does every Stihl 020 AV have the same chain brake?
Do not assume so. Confirm your saw’s version and brake parts using its serial number and matching parts information.
Can I force the clutch cover off if it is stuck?
No. Stop and check the brake position and the manual’s removal procedure. Forcing the cover can damage parts or release stored spring tension.
Should I lubricate the brake band?
No. Keep brake friction surfaces clean and dry. Oil or grease can impair braking.
Can I keep using the saw if the brake does not engage?
No. A brake that fails to engage can let the chain continue moving during kickback. Do not cut until the brake passes the manual’s test.
What torque should I use on the cover fasteners?
Use the value in the service information for your exact version. Do not use a generic torque value.
Can I test the brake by making a cut?
No. Use the manual-prescribed check. Do not use a cutting test or rev the engine with the brake engaged.
Does a chain that moves at idle mean the brake band is bad?
Not by itself. Stop the saw and check the correct idle specification with suitable equipment; have the brake inspected before returning the saw to service.
Can I use any bar and chain listed for an 020 AV?
No. Match pitch, gauge, and drive-link count to the bar markings and the saw’s correct documentation. Do not infer them from the model name.
When should I hand the repair to a technician?
When you lack the correct manual, parts, spring compressor, or safe removal procedure, or when the brake still binds or fails its documented test.
Final check before the next cut
The safe repair path is straightforward: confirm the version, control the spring risk, inspect before replacing parts, and test by the correct manual. Never guess at fit, torque, or adjustment. If the brake does not engage and release positively, keep the saw out of service until the fault is corrected.
(This article was written by one of our staff writers, Robert Callahan. Visit our Meet the Team page.)
