Stihl MS 291 Bar & Chain (Replacement Guide)
The STIHL MS 291 commonly takes a 16–20-inch bar, but bar length alone does not identify the right replacement chain. Match the bar mount, chain pitch, drive-link gauge, and exact drive-link count to your saw and sprocket. Check the bar and chain markings, confirm the owner’s manual, then fit, tension, and oil the assembly before cutting.
A saw can look ready to work and still be set up wrong. I have seen owners bring in a new chain that matched the bar length but not its drive-link count. It could not be fitted correctly, and the trip to the shop had to wait. A quick check of four markings before you buy prevents that problem.
Equipment Setup, Compatibility & Safety Preparation
Match all four fit details
Pitch is the spacing between chain rivets, stated as a fraction of an inch. Gauge is the thickness of the drive links that sit in the bar groove. Drive-link count is the number of links that run inside that groove. The bar mount is the pattern that fits the saw’s studs and oiling points.
STIHL lists bar lengths commonly from 16 to 20 inches (40 to 50 cm) for the MS 291, subject to market and equipment version. Many setups use 3/8-inch pitch. However, gauge and link count can differ, so do not order by bar length alone.
| Bar length example | Common drive-link count example | What to confirm |
|---|---|---|
| 16 in. | 60 | Actual bar and chain markings |
| 18 in. | 66 | Actual bar and chain markings |
| 20 in. | 72 | Actual bar and chain markings |
These are examples, not a promise that every MS 291 uses those counts. The numbers can change with chain pitch, gauge, and bar design. Check the bar stamp and chain packaging, or give a dealer the saw’s serial number and current part markings.
A simple buying check is: bar mount, pitch, gauge, then drive-link count. The chain pitch must match the drive sprocket as well as the bar. If one item differs, do not try to force the parts together.
Choose a practical bar length
The MS 291 has a displacement of 55.5 cm³. A longer bar can reach farther across a log, but it also gives you less margin for control and may add cutting load. Choose the shortest approved bar that suits the work, and do not exceed the manual’s allowed setup.
In my shop, I ask what the saw will cut most often before recommending a bar. A shorter bar may be easier to handle for routine firewood work. If you regularly cut larger wood, use only a bar length listed for your exact saw, and get qualified help if the job exceeds your training.
Replace the bar and chain
Chain tension is the adjustment that keeps the drive links seated in the bar groove while letting the chain move by hand. Correct tension helps prevent the chain from coming off, but excessive tension can cause wear. Make adjustments with the engine off and the chain cool.
- Engage the chain brake. Shut the engine off and let the saw cool.
- Loosen the bar nuts. Release the brake only as directed in the manual if needed to remove the cover.
- Remove the clutch cover, bar, and old chain. Note how the chain sits around the sprocket.
- Fit the new bar onto the studs. Check that its oil hole lines up with the saw’s oil outlet.
- Fit the chain around the drive sprocket and into the bar groove. Match the cutter direction to the diagram in the manual or on the saw.
- Refit the cover and nuts. Lift the bar nose, then adjust tension as the manual directs.
- With the engine off, pull the chain around the bar by hand using gloves. Drive links should stay in the groove, and the chain should move without binding.
- Tighten the bar nuts while holding the bar nose up. Recheck tension after the first short run and again once the chain cools.
Do not run a chain that binds, hangs loose, or fails to move by hand. Stop and recheck its fit and tension first.
Confirm oiling and safety parts
Fill the oil tank with dedicated chainsaw bar-and-chain oil. Do not use used motor oil. Oil flow is not one fixed rate for every setup, so use the manual’s instructions rather than guessing at an amount. Before cutting, confirm the chain receives oil as described in the manual.
Inspect the chain brake, throttle lockout, chain catcher, controls, bar rails, and fasteners. Wear a helmet with face and eye protection, hearing protection, chainsaw-protective legwear, gloves, and suitable boots. Clear bystanders and plan escape routes before felling or bucking.
Next step: If any marking is unreadable, stop before ordering. A STIHL dealer can identify the correct combination from the saw’s details and the bar or sprocket markings.
Field Cutting & Landscaping Operation
A correct replacement assembly still needs a safe pre-start check. Refuel with the correct mix, fill the oil tank, and confirm the chain stops at idle. Then use the saw with a firm grip and a clear work area. If oil delivery, chain brake action, or idle behavior is wrong, do not cut.
Before starting
The MS 291’s stated fuel mix is 50:1 with suitable two-stroke oil. Use fresh fuel mixed at that ratio, and never run straight gasoline. The manual lists a nominal idle speed of 2,800 rpm and maximum engine speed of 13,000 rpm; service adjustments and market versions may differ. Do not tune the carburetor by guesswork.
Engage the chain brake, start the saw on stable ground, and follow the cold-start steps in the manual. Keep the chain clear of people and objects. As the engine warms, release the choke as directed.
Check that the engine idles steadily and that the chain does not move at idle. Confirm brake function and chain oil delivery. If the chain moves at idle, stop and have the fault corrected. If oil is not reaching the chain, stop and check the oil level and the manual’s troubleshooting steps.
During the cut
Use a two-handed grip and stable footing. Keep the bar nose away from branches and logs; contact with the upper nose area can cause rotational kickback, which can throw the bar up and back. A sharp, correctly fitted chain and working chain brake reduce risk, but do not remove it.
Cut below shoulder height and avoid pinching the bar. Engage the brake when moving between cuts, and shut the engine off before clearing a jam or making an adjustment. For felling, plan the direction, notch, and escape route. If tree lean, size, defects, or nearby hazards exceed your training, use a qualified arborist. Follow applicable OSHA rules and ANSI Z133 work practices.
Next step: Stop if the saw smokes heavily, gets unusually hot, cuts poorly, or needs force to feed. A dull chain or a fault needs attention, not more pressure.
Maintenance, Sharpening & Tuning
Routine care protects the replacement parts and helps the saw cut as intended. Clean the bar groove and oil hole, inspect the rails and chain, and sharpen to the exact chain maker’s settings. Chain types can require different file sizes and angles, so identify the chain before sharpening.
File size, angles, and depth gauges
A depth gauge is the small projection ahead of each cutter that controls how much wood the cutter takes. Filing it too low can make the chain grab more aggressively. Use the depth-gauge tool specified for the exact chain, rather than judging the height by eye.
For common STIHL full-size 3/8-inch chain, the round file is often 5.2 mm, the top-plate filing angle is commonly 30 degrees, and the depth-gauge setting is commonly 0.65 mm (0.025 in.). These values are not universal for every chain sold for an MS 291. Some chain types use a different file size or sharpening method. Check the chain code and its packaging or the manufacturer’s sharpening chart first.
| Chain detail | Common full-size STIHL 3/8-in. reference | Verify before filing |
|---|---|---|
| Round file diameter | 5.2 mm | Chain type and filing instructions |
| Top-plate angle | 30° | Angle shown for that chain |
| Depth-gauge setting | 0.65 mm (0.025 in.) | Correct matching gauge tool |
Keep cutters even in length and file at the specified angle. Use a file guide if you are unsure how to hold the file. Do not file depth gauges by guesswork, and replace a chain with cracked, badly damaged, or excessively worn parts.
Inspect the bar and chain
With the saw off and cool, clean the groove and oil hole. Look for burrs, uneven rail wear, or rails that spread apart. Turn the bar over at intervals if the manual recommends it; this can help distribute wear. Replace a damaged bar rather than trying to correct serious rail damage with a file.
Check chain tension after the first run and after the chain cools. A new chain can need adjustment as it seats. If it repeatedly loosens, inspect the tensioner, sprocket, bar, and chain for wear or damage.
Troubleshoot poor cutting
A dull chain often makes fine dust rather than clear chips, cuts slowly, or pulls to one side. Stop and sharpen it correctly. Do not force it through wood; excess pressure strains the saw and can reduce control.
If performance remains poor, check for the correct fuel mix, a clean air filter, chain oil delivery, and a correctly fitted chain. Do not change carburetor settings to cover up a problem. A lean-running two-stroke can overheat and seize. If fuel is stale, a restriction or leak is suspected, or the cause is unclear, have the saw serviced.
Next step: Use the chain’s identification code to find the exact sharpening instructions. If the code is missing, take the chain or a clear photo of its markings to a STIHL dealer.
Storage, Seasonal Care & Practices to Omit
Storage care helps protect the bar, chain, and engine between jobs. Clean the saw after it cools, inspect the filter and sprocket area, and cover the chain before storage. Follow the manual’s fuel and seasonal storage steps for the fuel you use.
After work, shut off the saw and let it cool in a clear area. Clean debris from around the sprocket cover and cooling fins, then inspect the air filter as the manual directs. Store the saw dry, with the chain covered.
For longer storage, empty or stabilize fuel as directed by the manual and fuel type. Follow its instructions for running the saw before storage and for restarting it later. Never use straight gasoline or an incorrect oil ratio in the two-stroke engine.
A final check before the next outing saves time: confirm the chain is sharp, tension is correct, the bar oil tank is full, and the fuel mix is fresh. If you find damage or a fault, fix it before starting.
Frequently asked questions
What bar length fits a STIHL MS 291?
STIHL lists 16–20 inches (40–50 cm) commonly, depending on market and equipment version. Check your manual before fitting a different length.
Does every MS 291 use the same chain?
No. Pitch, gauge, drive-link count, and bar mount must all match. Bar length alone is not enough to choose a chain.
What pitch is common on the MS 291?
Many MS 291 setups use 3/8-inch pitch. Confirm the pitch stamped on the bar and match it to the drive sprocket and chain.
How many drive links does an 18-inch chain need?
Some 18-inch setups use 66 drive links, but not all do. Read the bar and chain markings before ordering.
What file size is used for an MS 291 chain?
It depends on the chain type, not just the saw model. A common STIHL full-size 3/8-inch chain uses a 5.2 mm round file; verify the chain code first.
What sharpening angle should I use?
A common reference for STIHL full-size 3/8-inch chain is 30 degrees. Follow the exact chain maker’s instructions if they specify another angle.
What fuel mix does the MS 291 use?
The stated mix is 50:1 with suitable two-stroke oil. Check the machine’s manual and never use straight gasoline.
How tight should the chain be?
Set it by the manual’s procedure with the engine off and chain cool. Drive links must stay seated in the groove while the chain can still be pulled around by hand.
Can I use motor oil in the bar-oil tank?
Use dedicated chainsaw bar-and-chain oil. Do not use used motor oil.
Why does the saw cut slowly after I replaced the chain?
Check chain direction, sharpness, tension, and compatibility. Also confirm oil delivery. Stop if the chain binds, smokes, or behaves abnormally.
(This article was written by one of our staff writers, David Hensley. Visit our Meet the Team page.)
