Stihl MS 291 Pitch & Gauge (Spec Guide)
The common STIHL MS 291 setup is a 3/8-inch pitch chain with a .050-inch (1.3 mm) gauge, but check the bar, chain, and sprocket before buying parts. Match the chain’s drive-link count to the bar marking, too. Many saws use 16-, 18-, or 20-inch bars; the correct chain depends on the exact bar.
A pitch or gauge mismatch can keep a chain from seating and tracking as it should. The good news is that checking the markings takes only a moment, and matching the parts is straightforward once you know what to look for.
I use the same order each time I identify a setup: bar marking, chain marking, drive-link count, then sprocket pitch. That order helps prevent the common mistake of choosing a chain by bar length alone.
Identify the MS 291 pitch, gauge, and drive links
Pitch describes the spacing between the chain’s rivets; gauge is the thickness of its drive links, which sit inside the bar groove. Drive-link count is the number of links that travel around the bar. All three must suit the bar and saw.
The common MS 291 chain setup is 3/8-inch pitch and .050-inch (1.3 mm) gauge. Treat that as a starting point, not a replacement for checking your saw. Equipment can vary by bar, chain, and market, so read the markings on the parts fitted to your specific machine.
| Specification | Common MS 291 setup | What must match |
|---|---|---|
| Chain pitch | 3/8 in. | The drive sprocket and bar nose sprocket, if fitted |
| Chain gauge | .050 in. (1.3 mm) | The bar groove |
| Bar length | 16, 18, or 20 in. are common | The bar and chain listed for your saw |
| Drive-link count | Depends on the bar | The bar’s stamped specification |
Look for the bar’s stamped information near the mounting end. It may show length, pitch, gauge, and drive-link count, but formats differ. The chain may carry identifying marks on its drive links or packaging. If a marking is worn or unclear, check the STIHL manual and the parts information for the exact bar and chain rather than guessing.
Pitch needs special care. A chain labeled 3/8 inch is not automatically the right chain: gauge and link count still matter, and the chain pitch must suit the sprocket. A gauge mismatch can prevent proper seating in the bar groove. A wrong link count can leave the chain too loose or too tight to adjust correctly.
Choose a bar and chain that fit
A compatible chain is one listed for the exact bar and saw combination. Bar length alone does not identify the right chain. Confirm the pitch, gauge, and drive-link count from the bar marking or manufacturer’s parts information before you buy or install a replacement.
Many MS 291 saws are paired with 16-, 18-, or 20-inch bars. Availability and approved combinations may vary by market. Do not assume that every bar sold for an MS 291 uses the same chain length or link count.
A quick parts check
- Read the bar’s stamped pitch and gauge.
- Find the drive-link count on the bar, chain package, or verified parts listing.
- Confirm the replacement chain’s pitch, gauge, and link count.
- Confirm that the drive sprocket pitch matches the chain.
- If the bar or sprocket has been changed, verify the entire combination instead of relying on an old chain label.
Illustrative fit check: Suppose your bar is stamped 18 inches, 3/8-inch pitch, and .050-inch gauge. You still need the listed drive-link count; the 18-inch length does not tell you that by itself. If a replacement chain matches the pitch and gauge but has a different number of links, stop and verify the bar specification before fitting it.
I have seen this mix-up at the bench: a person brings in a chain chosen because “it’s 18 inch.” The useful question is not just the length. It is whether the chain matches that particular bar and sprocket in all three details.
Equipment Setup and Safety Prep
Before fitting or running a chain, check that the parts match and the saw’s safety features work. Set up on stable ground with the engine off and cool. Wear suitable personal protective equipment, and follow the saw’s current manual and local safety rules.
Start with a clean, secure saw. Engage the chain brake before handling the chain, and use gloves when working around sharp cutters. Check that the chain is facing the right way: on the top run, the cutting edges point forward toward the bar nose.
Follow the manual to install and tension the chain. Tension a cool chain so its drive links remain engaged in the bar groove, while the chain can still move by hand when the brake is released. Do not check chain movement with the engine running. Recheck tension after the chain warms, following the manual’s instructions; a hot chain contracts as it cools, so avoid tightening it too far while hot.
Before starting, check the chain brake, throttle interlock, chain catcher, and lubrication system. Fill the oil tank with the specified bar-and-chain oil. The MS 291’s fuel mix is 50:1 gasoline to approved two-stroke engine oil. Use fresh fuel and the fuel grade specified in the current STIHL manual. Never use straight gasoline.
Wear a helmet, eye and hearing protection, chainsaw-protective legwear, gloves, and suitable boots. Check footing, overhead hazards, bystanders, and escape routes before cutting. Follow applicable ANSI Z133 guidance and OSHA rules where they apply.
Maintenance, Sharpening, and Tuning
A sharp, correctly fitted chain cuts more cleanly than a dull one forced through wood. Use the file size and sharpening angles specified for the exact chain model. The MS 291’s common pitch does not, by itself, identify every cutter or sharpening requirement.
For many standard STIHL 3/8-inch chains, the round file is 5.2 mm (13/64 inch) and the top-plate filing angle is 30 degrees. Check the chain’s markings, packaging, or STIHL instructions before using those values; special chain types may call for different instructions. A file that is too small or too large will not shape the cutter correctly.
| Item | Common reference | Check before sharpening |
|---|---|---|
| Chain pitch | 3/8 in. | Chain markings and sprocket |
| Round file | 5.2 mm (13/64 in.) for many standard 3/8-in. chains | Exact chain type |
| Top-plate filing angle | 30° for many standard STIHL chains | Chain instructions or sharpening marks |
| Depth-gauge setting | Use the specified depth-gauge tool | Exact chain type and instructions |
Secure the bar, engage the brake as appropriate for your sharpening method, and wear gloves. File each cutter with even strokes, keeping the specified angle and file position. Maintain a consistent cutter length and sharpen cutters on both sides. If the chain has damaged cutters, uneven lengths, or other wear beyond routine filing, have it assessed or replace it.
Depth gauges control how much wood each cutter takes. After sharpening, check and adjust them only with the gauge tool and method specified for the chain. Do not lower them by eye; incorrect depth can change cutting behavior and increase kickback risk.
A chain that cuts slowly, produces fine dust instead of chips, or pulls to one side may need sharpening or inspection. Also check for poor lubrication, a pinched bar, or damage. Do not force a dull chain through wood; stop the saw and correct the cause.
The MS 291’s reference speed is about 2,800 rpm at idle and 13,000 rpm maximum. These are specifications, not targets for adjustment. Do not tune maximum speed by ear. Follow the manual, and have carburetor or tachometer checks done by a qualified technician.
Field Cutting and Landscaping Operation
Safe cutting starts with a sound setup and a controlled work area. Start the saw using the manual’s cold- or warm-start procedure, with the saw secured and the chain brake engaged. Keep both hands on the saw and your footing stable while cutting.
Keep the bar nose clear of the wood. Contact with the upper quadrant of the nose can cause rapid rotational kickback toward the operator. Maintain a firm two-handed grip, plan for pinching and limb movement, and do not cut above shoulder height. If the chain stops cutting well, stop and inspect it rather than pushing harder.
Storage and Seasonal Care
Clean and inspect the saw before storage, with the engine stopped and cool. Clear debris from the bar groove, oil ports, sprocket area, and cooling fins. Check chain condition and tension, and follow the manual for fuel handling and storage.
After work, engage the chain brake, stop the engine, and let the saw cool before cleaning. Remove the bar and chain if needed for a thorough check. Make sure the oil ports are clear and the bar groove is not packed with debris; poor oil flow can damage the bar and chain. Store the saw and fuel as directed in the manual, away from ignition sources and out of children’s reach.
Frequently asked questions
These quick answers cover the details most likely to matter when replacing or checking an MS 291 chain. Use them as a first check, then confirm uncertain parts against the bar marking, chain identification, and current STIHL instructions for your market.
What pitch does the STIHL MS 291 commonly use?
A common setup uses 3/8-inch pitch. Confirm the fitted chain and sprocket markings; do not select a chain by pitch alone.
What chain gauge is common on an MS 291?
The common gauge is .050 inch, or 1.3 mm. The gauge must match the groove in your bar.
Are all MS 291 chains the same drive-link count?
No. Drive-link count depends on the specific bar. Read the bar marking or check its verified parts listing.
What bar lengths are common for the MS 291?
Common options include 16, 18, and 20 inches. Use only a bar and chain combination listed for your exact saw and market.
Is every 3/8-inch chain right for this saw?
No. Pitch, gauge, drive-link count, and sprocket compatibility all matter. Match the chain to the bar and sprocket.
What file size is used for a common 3/8-inch STIHL chain?
Many standard STIHL 3/8-inch chains use a 5.2 mm (13/64-inch) round file. Check the exact chain type before sharpening.
What sharpening angle should I use?
A 30-degree top-plate angle is common for many standard STIHL chains. Follow the sharpening marks or instructions for your specific chain.
What fuel mix does the MS 291 use?
Use a 50:1 gasoline-to-approved two-stroke-oil mix, with fresh fuel and the fuel grade specified in the current manual.
Can I check or adjust maximum engine speed by ear?
No. The approximate maximum reference is 13,000 rpm, but it is not an adjustment target. Follow the manual or use a qualified technician.
What should I check if the chain will not cut cleanly?
Stop the saw. Check sharpness, chain tension, oil delivery, and visible damage. Do not force a dull chain through the cut.
(This article was written by one of our staff writers, David Hensley. Visit our Meet the Team page.)
