Stihl MS 291 Displacement (Specs & Bars)
The STIHL MS 291 has a 55.5-cm³ single-cylinder, two-stroke engine. Common configurations use 16-, 18-, or 20-inch guide bars, but bar length alone does not confirm fit. Match the bar’s pitch and gauge to the chain, then confirm the chain’s drive-link count and the combination’s approval in your manual or STIHL fitment data.
If you’re comparing listings, it’s easy to focus on the number of inches and miss the details that decide whether a bar and chain actually fit. I’ve seen that confusion come up often in equipment checks: two bars with the same length can still call for different chains. Here’s how to read the MS 291’s key specs and choose a compatible setup without guessing.
STIHL MS 291 displacement and engine specifications
Displacement is the total volume swept by the piston as it moves through the cylinder. The MS 291’s displacement is 55.5 cm³, or about 3.39 cubic inches. That figure identifies engine size; by itself, it does not tell you which bar or chain fits.
| Specification | MS 291 detail | What it tells you |
|---|---|---|
| Displacement | 55.5 cm³ | Engine size |
| Engine type | Single-cylinder, two-stroke | The engine’s basic design |
| Common bar lengths | 16, 18, or 20 inches | Options found in common configurations, subject to market and fitment |
| Common chain pitch | 3/8-inch standard pitch | A chain dimension that must match the bar |
| Approximate idle speed | 2,800 rpm | A reference value, not a do-it-yourself tuning target |
| Approximate maximum engine speed | 13,000 rpm | Confirm service data before testing or adjustment |
The listed speed figures are approximate. Carburetor settings and tachometer checks should follow model-specific service information. A saw that idles poorly or runs badly needs proper diagnosis, not a guessed adjustment.
Fuel is also part of the engine specification in practice. Use fresh fuel mixed at 50:1 by volume with suitable air-cooled two-stroke oil, such as STIHL HP or HP Ultra. Follow the manual for fuel and oil requirements.
Key takeaway: 55.5 cm³ is the displacement to use when checking the model. It does not replace the manual or bar markings when choosing cutting gear.
Bar length, pitch, gauge, and chain fit
A guide bar supports the chain, and the chain must match the bar’s dimensions. Pitch describes the spacing between chain drive links; gauge is the thickness of the drive links that sit in the bar groove. A correct fit depends on both measurements and the required drive-link count.
Common MS 291 setups use 3/8-inch standard pitch. That is not the same as 3/8-inch low-profile pitch. The bar’s stamp is the best place to check its pitch and gauge. The chain package or manufacturer’s fitment information should show the matching specifications and drive-link count.
| Bar length | Typical use to consider | What to verify before buying |
|---|---|---|
| 16 inches | A shorter setup for smaller-diameter cutting | STIHL approval, pitch, gauge, and chain drive-link count |
| 18 inches | A middle option for mixed cutting needs | The same details, plus the bar’s exact part or fitment information |
| 20 inches | A longer setup for suitable larger cuts | Approval for the saw and exact chain match; longer is not automatically better |
These are not universal pairings or guarantees of suitability for a particular tree. Approved combinations can vary by market and bar-and-chain setup. Check the operator’s manual and current STIHL fitment information for your saw.
When I review a replacement setup, I treat the bar stamp as a starting point, not a complete order form. A listing that says “18-inch bar for MS 291” may still leave out pitch, gauge, or chain length. Confirm all three before purchasing.
Key takeaway: Match the saw, bar, and chain as a set. Do not infer compatibility from bar length alone.
Equipment Setup and Safety Preparation
Safe setup starts before the engine runs. Use the manual for the exact saw and installed cutting attachment, and check the saw’s controls and condition. Good PPE and a clear work area do not make a risky cut safe, but they are essential parts of preparation.
Before cutting, wear chainsaw-rated leg protection, a helmet, eye and hearing protection, gloves, and suitable boots. Inspect the chain brake, throttle lockout, chain catcher, bar, chain tension, and lubrication. Do not use the saw if a safety part is damaged or does not work.
Prepare the site, too. Keep other people clear, identify an escape route, and look for overhead hazards, lean, and likely wood movement. If the tree or cut presents a hazard you cannot assess, get help from a qualified professional.
For bar and chain installation, first stop the engine and follow the manual’s procedure. Confirm that the chain direction is correct and that the drive links sit in the bar groove. Adjust tension as instructed, then recheck it before use. Do not assume that a chain fits just because it can be placed on the bar.
Key takeaway: Verify the complete cutting attachment and safety systems before starting. A compatible bar and chain are only one part of a safe setup.
Field Cutting and Landscaping Operation
The MS 291’s bar choice should suit both the approved setup and the cut you plan to make. A longer bar can reach farther into a cut, but it does not make every task easier. Keep the bar nose clear of wood and obstructions, maintain two-handed control, and use planned cuts suited to the tree or log.
Start the saw according to the manual’s cold- or warm-start procedure, on stable ground with the chain clear. At idle, the chain should stop. Check that the chain brake functions as intended; do not operate the saw if it is damaged or disabled.
A critical hazard is kickback: contact with the upper quadrant near the bar nose can make the saw rotate rapidly toward the operator. Avoid cutting with the nose and keep it away from branches, logs, and other objects. Use a sharp, correctly tensioned chain, and do not force it through wood.
Felling and difficult tree work require training and a clear assessment of the hazards. If the tree is leaning, damaged, under tension, or near people or structures, use qualified help rather than treating a longer bar as a solution.
Key takeaway: Use a bar length approved for your saw and suitable for the cut. Keep the nose clear and stop if the cut or work area becomes unsafe.
Maintenance, Sharpening, and Tuning
Routine checks help keep the cutting attachment in working order. Stop the engine before cleaning or adjusting, and let the saw cool. Follow the manual’s service schedule; do not use approximate speed figures as a substitute for model-specific tuning data.
After use, check the chain for damage and tension, inspect the bar, and confirm that the chain is receiving lubrication. Clean debris from the saw and service the air filter as specified. If the chain is dull, stop and sharpen or replace it before continuing. Forcing a dull chain through wood can make control harder and add strain.
A chain that repeatedly loosens, a damaged bar, or poor cutting performance calls for inspection rather than guesswork. Confirm that the chain and bar match, then consult the manual or a qualified service provider. Carburetor adjustment should follow service data and suitable test methods; do not turn adjustment screws by guess.
Key takeaway: Keep the bar and chain clean, sharp, correctly tensioned, and lubricated. Stop the engine before maintenance.
Storage and Seasonal Care
Proper storage starts with a clean, inspected saw. Follow the operator’s manual for fuel handling and storage, especially when the saw will sit unused for a long period. Keep the bar and chain protected, and store the saw where it is dry and out of reach of children.
Before putting it away, stop the engine and let it cool. Remove debris, check for damage, and note any maintenance needed before the next use. For longer storage, follow STIHL’s instructions for the fuel system and the specific fuel product in use; storage steps can differ by fuel type.
Key takeaway: Clean and inspect before storage, then use the manual’s directions for fuel and seasonal care.
Conclusion and FAQs
The key numbers are simple: 55.5 cm³ displacement, common 16-, 18-, and 20-inch bar options, and common 3/8-inch standard-pitch chains. The right setup still depends on the approved combination and exact bar and chain markings. Use these checks to narrow your options, then confirm the fit before buying.
How many cc is a STIHL MS 291?
The MS 291 has 55.5 cm³ displacement, equivalent to about 3.39 cubic inches.
What bar lengths are common on the MS 291?
Common configurations use 16-, 18-, or 20-inch bars. Availability and approved combinations vary by market and setup.
Can I use any 18-inch bar on an MS 291?
No. Check that the bar is approved for the saw and match its pitch and gauge to the chain.
What chain pitch does the MS 291 use?
Common setups use 3/8-inch standard pitch. It is not the same as 3/8-inch low-profile pitch.
How do I find the right chain length?
Check the bar’s markings and chain fitment information for the correct drive-link count. Do not estimate it from bar length.
Does the MS 291 use a 50:1 fuel mix?
Use fresh gasoline mixed 50:1 by volume with suitable air-cooled two-stroke oil, and follow the operator’s manual.
What are the MS 291’s approximate engine speeds?
Approximate figures are 2,800 rpm at idle and 13,000 rpm maximum. Use model-specific service data for checks or adjustment.
Can I put a longer bar on the saw for bigger cuts?
Only if that bar-and-chain combination is approved for your saw. A longer bar is not automatically the right or safer choice.
What should I check before starting after changing the bar?
Confirm the chain matches the bar’s pitch and gauge, verify its drive-link count and direction, set tension as instructed, and check safety controls.
What is the main kickback risk to remember?
The upper quadrant near the bar nose can cause rapid rotational kickback if it contacts wood or an obstruction. Keep the nose clear and do not operate with a faulty chain brake.
(This article was written by one of our staff writers, Marcus Thorne. Visit our Meet the Team page.)
