Stihl 028 AV Bar Stud Replacement (Step-by-Step)
To replace a bar stud on a STIHL 028 AV, first confirm the correct part and thread details using the saw’s serial number and parts listing. Disconnect the spark-plug boot, remove the bar and chain, and inspect the mounting threads. Install the verified stud without force, then refit and check the bar, chain tension, and free chain movement before cutting.
Many 028 AV saws have been kept working through years of careful maintenance. A loose bar stud can undo that care quickly: the bar may shift under load, and the chain can lose tension. I treat a stud replacement as a mounting repair, not just a quick hardware swap. The exact part and safe installation method matter.
Prepare the saw and confirm the replacement stud
This preparation protects you from accidental starting and prevents a mismatched part from damaging the crankcase. The 028 AV is about 47 cm³, but model age and production differences mean you should verify the stud against the saw’s serial-number-specific parts listing before removing anything.
- Let the engine cool, place the saw on a stable bench, and wear eye protection and cut-resistant gloves.
- Remove the spark-plug boot so the engine cannot start. If you must tip the saw, safely contain fuel and oil to prevent spills.
- Identify the exact replacement stud through a STIHL parts diagram or service source matched to the serial number. Do not choose one only because it looks similar.
- Check whether the listed part and service procedure specify a threaded stud or another mounting arrangement. Do not assume the removal method or thread size.
- Read the guide-bar stamp and sprocket marking to confirm chain pitch and gauge. The bar, chain, and sprocket must match.
The 028 AV’s displacement does not identify its bar setup or stud specification. If you cannot confirm the replacement part and installation method, pause and check the correct parts or service information before proceeding.
Remove the bar, chain, and damaged stud
Expose the mounting area without putting side load on the stud or its housing. The chain brake must be released to remove and reinstall the sprocket cover; keep the engine disabled and handle the chain carefully while the cover is off.
- With the plug boot disconnected, release the chain brake.
- Loosen and remove both bar nuts, then lift off the sprocket cover. If the cover will not come free, do not force it; check that the brake is released.
- Back off the chain tensioner until the chain is slack. Remove the bar and chain, keeping the chain’s cutters away from your hands.
- Inspect the stud, mounting face, bar slot, nuts, and visible crankcase area. Look for damaged threads, cracks, metal debris, fretting, or an elongated bar slot.
- Confirm the replacement part and removal procedure again. If the stud is intact enough to grip and the service method permits it, use a suitable stud extractor or a controlled double-nut method. Turn steadily and keep the tool aligned with the stud.
- Stop if the stud will not move with controlled effort, or if the housing threads appear stripped or cracked. Do not lever against the crankcase, force the stud, or substitute an oversized part.
A double-nut method means locking two compatible nuts against each other on the exposed stud, then turning the inner nut to rotate the stud. It is only suitable when the stud provides enough clean, usable thread and the correct thread is known. If either condition is missing, use the specified extractor or seek service.
Install the replacement and refit the bar
The new stud must start straight and seat according to the applicable service procedure. Cleanliness and alignment matter more than force: cross-threading or over-tightening can damage the crankcase and leave the bar unable to clamp securely.
- Remove loose debris from the mounting hole without cutting, enlarging, or damaging its threads.
- If the verified design uses a threaded stud, start it by hand. It should turn smoothly at first. If it binds, back it out and check alignment and thread condition.
- Seat the stud only to the applicable STIHL service specification. Do not invent a torque value or tighten against resistance. If the correct specification is unavailable, have the installation assessed rather than guessing.
- Do not add threadlocker or use heat unless the service procedure specifically calls for it.
- Fit the bar and correctly matched chain. Make sure the drive links engage the sprocket and sit fully in the bar groove.
- Reinstall the sprocket cover with the chain brake released. Raise the bar nose while adjusting chain tension, then tighten both bar nuts evenly and securely. Do not over-torque them.
| Check | What to confirm | Stop if… |
|---|---|---|
| Replacement part | Matches the saw’s serial-number-specific parts listing | Part or thread details are uncertain |
| Crankcase mounting | Threads and surrounding area are sound | Threads are stripped or housing is cracked |
| Bar and chain | Pitch and gauge match the sprocket and bar markings | Components do not match |
| Bar slot | Sits flat over the studs and is not distorted | Slot is elongated or damaged |
| Clamping | Both nuts tighten evenly and hold the bar | Bar shifts or tension will not hold |
The table is a go/no-go check, not a substitute for the service procedure. A bar that moves after tightening is not safe to use.
Check the repair before starting the engine
A correct installation should hold the bar securely and let the chain travel by hand without binding. Keep the spark-plug boot disconnected during these checks. This catches assembly problems before engine power adds load.
- With gloves on, pull the chain along the bar by hand. Keep your fingers clear of the cutters.
- Confirm the chain stays engaged with the sprocket and moves freely. Check that it has no abnormal side play.
- Recheck chain tension after rotating the chain. The chain should remain properly seated in the bar groove; use the saw’s applicable manual for the exact tension check.
- Check that the bar does not rock or shift when you handle it. Confirm both nuts remain secure.
- Clear tools from the saw, reconnect the plug boot, and start only after the cover is installed and the chain brake is engaged.
- At idle, verify that the chain does not move. Stop the saw if it moves at idle, binds, derails, or the bar shifts. Do not continue cutting to “see if it settles.”
After the mounting repair, also confirm chain lubrication before cutting. Clear debris from the bar groove and oil holes, and use a matched bar, chain, and sprocket. If the saw needs engine tuning, use the applicable STIHL service data and tachometer procedure; do not guess at RPM settings.
Common repair scenarios and decisions
These workshop-style examples show how I separate a straightforward replacement from a repair that needs more assessment. They are diagnostic scenarios, not claims about a particular 028 AV or a specific repair history.
- The stud turns out cleanly, and the mounting threads look sound. Verify the new part and prescribed installation method, install it carefully, then complete the bar and chain checks. Do not skip the hand-rotation test.
- The stud spins but will not tighten. That may indicate damaged housing threads or another mounting fault. Stop; an oversized or improvised stud can make the damage worse.
- The bar still shifts after the replacement. Check that the bar sits flat, both nuts clamp evenly, and the bar slot is not worn or distorted. If the mounting surface or threads are damaged, do not cut until the housing has been assessed.
- The chain binds after refitting. Stop and check chain direction, drive-link seating, pitch and gauge match, bar groove condition, and tension. Do not start the engine while it binds.
The important distinction is whether the mounting point can securely retain the verified stud. If you cannot establish that, replacement alone is not a safe fix.
Aftercare and next-use checks
Routine checks help catch a loose mounting point before it becomes a field failure. Inspect the hardware whenever you remove the bar, and avoid trying to make damaged parts work by tightening harder.
- Check both studs, nuts, the bar slot, and the mounting face whenever the bar is off. Replace damaged nuts and a bar with an elongated or distorted slot.
- Keep the bar groove and oil holes clear. Confirm oil delivery before cutting.
- Follow the chain maker’s filing angles and depth-gauge specifications; do not set depth gauges by guesswork.
- Store the saw with the chain covered and away from heat or ignition sources. For extended storage, follow the applicable manual’s fuel-system instructions.
- Before the next use, recheck stud security and chain tension.
For fuel, use a 50:1 mix only when using STIHL two-cycle oil labeled for that ratio. If using another oil or a different-period specification, follow the applicable 028 AV manual and oil label instead.
Frequently asked questions
These answers cover the checks owners most often need before finishing a bar-stud repair. The serial-number-specific parts listing and applicable service information take priority whenever the exact stud, mounting method, or specification is uncertain.
How do I find the correct bar stud for my 028 AV?
Use the saw’s serial number with a STIHL parts listing or service source. Do not rely on appearance alone.
Can I use a stud from another STIHL saw?
Only if a reliable parts reference confirms it is the correct replacement. Similar-looking studs may differ.
What torque should I use on the stud?
Use the applicable service specification. Do not guess or substitute the bar-nut torque.
Can I use threadlocker?
Not unless the relevant service procedure specifically calls for it. Unapproved products or methods can complicate service.
Should the chain brake be on when removing the sprocket cover?
No. Release the brake to remove and refit the cover. Keep the engine disabled during the work.
What if the stud spins without tightening?
Stop. The mounting threads may be damaged. Do not force an oversized or improvised stud into place.
Can I cut if the bar shifts slightly?
No. Stop using the saw until the mounting fault is corrected and the bar holds securely.
What if the chain binds during the hand check?
Do not start the saw. Check chain seating, component match, bar condition, and tension first.
Does the 028 AV always use the same bar and chain setup?
No. Check the bar stamp and sprocket marking. A common setup is not proof of what is fitted to your saw.
What fuel mix should I use after the repair?
Use 50:1 only with STIHL two-cycle oil labeled for that ratio. Otherwise, follow the applicable manual and oil label.
(This article was written by one of our staff writers, David Hensley. Visit our Meet the Team page.)
