Used Stihl MS 660 Chainsaw (Buyer’s Guide)
A sound used Stihl MS 660 can be a strong choice for demanding bucking and felling, but only if it is genuine, mechanically healthy, and correctly set up. Its 91.6 cm³ engine is not a casual-use upgrade. Check the saw’s identity, cold-start behavior, compression signs, safety systems, bar and chain match, and repair needs before agreeing on a price.
Could the saw that looks like a bargain turn into an expensive project after one cut? The MS 660’s power makes it useful in large wood, but age, hard use, poor repairs, and aftermarket changes can make two outwardly similar saws very different purchases.
I assess a used saw in stages: confirm what it is, inspect parts that can make it unsafe or costly to repair, then test how it runs. A seller’s claim that it “just needs a tune” is not a diagnosis. If the saw cannot be tested safely, value it as a repair project, not as a ready-to-work machine.
Is a used MS 660 the right saw for your work?
The MS 660 is a large-displacement, professional-style saw for demanding cutting, not light pruning or occasional small branches. Its 91.6 cm³ air-cooled, single-cylinder two-stroke engine is rated at about 5.2 kW (7.1 bhp). Buy one only if your work and skill justify its size and power.
A long bar does not make the saw a better fit for every job. Bar length should suit the wood, the correct chain and bar configuration, and your ability to control the saw. No bar recommendation overrides safe handling or the need for qualified help with hazardous felling.
Ask the seller for the saw’s history, including who serviced it, what parts have been replaced, and whether the crankcase, cylinder, carburetor, ignition, or muffler has been modified. Request the applicable manual and parts information. A genuine saw with available parts and a clear service history is easier to assess than an unidentified build assembled from mixed components.
| Your intended use | What to check | Buying guidance |
|---|---|---|
| Large-diameter bucking | Engine condition, oiling, matched bar and chain | Consider it only if you can handle the saw and its work safely |
| Professional felling | Brake, controls, structure, maintenance record, operator qualification | A sound saw is only one part of a safe felling system |
| Occasional small-wood cutting | Whether this much saw is needed at all | A smaller saw may be more suitable |
| Repair or parts project | Identity, missing parts, damage, parts availability | Price it as a project, not as a working saw |
I would not pay a premium based on appearance, a long bar, or a claim that the saw is “all original.” Those details do not prove its mechanical condition. The next step is to inspect the machine before discussing a final price.
How to inspect a used MS 660 before buying
A pre-purchase inspection should establish identity, safety, and likely repair needs. Look for damage and mismatched parts before starting the saw. A clean exterior helps you see details, but it does not prove that the engine is healthy or that the machine is genuine.
Start with the model identification and serial number. Ask a Stihl dealer to help verify the saw and check parts support; a badge or seller’s paperwork alone may not establish that every component is correct. Compare the saw with the applicable parts information, and ask about non-factory parts or modifications. Do not assume factory settings on a modified or uncertain machine.
With the engine off, check:
- Crankcase and handles: Reject cracks, loose mounts, or repairs that appear unsafe.
- Bar and chain: Look for damaged rails, excessive wear, a loose or mismatched chain, and a chain that does not match the bar’s stamped pitch and gauge.
- Sprocket cover and safety parts: Confirm that the chain catcher, guards, and controls are present and intact.
- Chain brake: Check that the brake is present and moves as intended. A visual check does not replace a functional test.
- Fuel system: Look for leaks, damaged lines, or a strong fuel odor that could indicate a spill or fault.
- Air and cooling areas: Heavy packed debris can point to neglected cleaning, though a clean saw does not prove good maintenance.
If the seller agrees to a test, ask to see a cold start. A warm saw may start more easily and can hide a cold-start complaint. Do not run a saw with a damaged brake, fuel leak, missing safety parts, or suspect bar and chain. If it cannot be started and tested, treat engine condition as unknown and reflect that in the offer.
Two common inspection cases illustrate the trade-off. A saw with worn consumable parts but a solid case and consistent service history may be a more sensible purchase than a shiny saw with unexplained modifications. A saw with a cracked case, failed brake, or uncertain identity is a poor candidate for work, even if it starts. These are evaluation examples, not a guarantee that any specific machine is sound.
Equipment Setup and Safety Preparation
Correct setup means a compatible cutting system, working safety parts, and the right protective gear before the engine runs. The MS 660’s power raises the stakes of a mismatch or fault. Follow the manual for the exact saw, and do not treat a successful start as proof that the saw is safe.
Confirm the bar’s stamped pitch and gauge, then match the chain to those markings and the required drive-link count. MS 660 setups commonly use 3/8-inch standard-pitch chain and .063-inch bar gauge, but verify the specific bar and saw rather than relying on a seller’s description. Drive-link count depends on the bar and setup.
Before starting, inspect chain tension and lubrication. Fill the chain-oil tank with suitable bar oil and the fuel tank with fresh gasoline mixed with Stihl two-stroke oil at 50:1, unless the applicable manual for that saw and oil directs otherwise. Never run straight gasoline or an unverified mix; inadequate lubrication can quickly damage the piston and cylinder.
Wear a chainsaw helmet with face and eye protection, hearing protection, chainsaw leg protection, gloves, and protective boots. Start the saw on stable ground, restrained as the manual specifies, with the chain brake engaged. Verify the chain does not move at idle and confirm that the brake and oiler work. Keep people clear of the work zone and plan an escape route before cutting.
Rotational kickback can happen when the upper quadrant of the bar nose strikes wood or another obstruction. The bar can snap up and back toward the operator. Keep that quadrant clear, hold the saw with both hands, and do not cut with the nose unless trained and equipped for that technique. For professional felling, follow ANSI Z133 and applicable OSHA 29 CFR 1910.266 requirements, including required separation between fellers.
Field Cutting and Landscaping Operation
Cutting safely requires matching technique to the wood, the saw, and the operator. The MS 660’s output does not remove the risks of kickback, pinching, falling limbs, or a tree’s lean. If a tree has defects, overhead hazards, or a dangerous lean, use a qualified tree-care professional rather than treating the saw as the solution.
For bucking, plan where the wood is under compression and tension so the bar is less likely to bind. Keep a stable stance, maintain two-handed control, and avoid cutting above shoulder height. If the chain becomes dull, stop to sharpen or repair it; do not force the saw through the wood.
For felling, assess the tree, its lean, defects, nearby structures, overhead hazards, and escape routes before cutting. Directional notches and an intact hinge are part of controlled felling, but no brief guide can teach safe felling across all tree conditions. Seek a qualified professional when the tree or site creates hazards, including barber-chair risk. Bar length is not a measure of what an operator can safely cut.
Maintenance, Sharpening, and Carburetor Tuning
Regular maintenance helps reveal wear before it becomes a failure, but it cannot make damaged parts safe. After use, clean the sprocket-cover area, bar groove, and cooling areas. Check the chain, bar, brake, and oil delivery before the next job, and follow the specific manual for service intervals and parts.
Set chain depth gauges to the chain maker’s specification. For applicable Stihl 3/8-inch chain, a typical depth-gauge setting is 0.65 mm (0.0256 in); confirm that the value applies to the chain installed. Use the correct depth-gauge tool and maintain cutter geometry. A wrongly filed chain can cut poorly or behave unpredictably.
Factory reference speeds are approximately 2,500 rpm at idle and 13,500 rpm at maximum engine speed. Confirm the applicable manual and tune with a tachometer, not by ear. An idle chain that moves, erratic running, or poor performance calls for diagnosis; avoid turning the high-speed screw to mask a problem. On a saw with unknown modifications, do not assume factory carburetor settings.
Storage and Seasonal Care
Good storage limits fuel-system and corrosion problems between jobs. Follow the manual for the machine’s storage procedure, and do not put a saw away with an active fuel leak or unresolved safety fault. A stored saw still needs a pre-use inspection before it returns to work.
After cutting, engage the brake and shut the engine down before cleaning or servicing. Let the saw cool before refueling or maintenance. Clean chips and debris from the cover, bar groove, and cooling areas; check chain tension after the saw cools. Store the saw securely, away from children and ignition sources, and use the manual’s guidance for fuel handling and longer storage.
Final buying decision and FAQ
A good purchase is a genuine, serviceable saw whose condition matches the price and your work. Do not let a low asking price, a fresh coat of paint, or a successful start replace inspection. If key safety parts fail or engine condition cannot be confirmed, pause the deal or budget for a qualified assessment before using it.
What should I verify first on a used Stihl MS 660?
Verify the model and serial information, then inspect the case, safety parts, bar, chain, and fuel system. Ask about service history and modifications. If identity or mechanical condition remains uncertain, do not treat it as a ready-to-work saw.
What is the MS 660 engine size and rated output?
The MS 660 has a 91.6 cm³ air-cooled, single-cylinder two-stroke engine rated at approximately 5.2 kW (7.1 bhp). Check the applicable manual for the exact saw and configuration.
What fuel mix does an MS 660 use?
The specified mix is 50:1 gasoline to Stihl two-stroke oil, using fresh fuel. Follow the manual for the specific saw and oil. Do not use straight gasoline or an unknown mix.
What chain pitch and bar gauge should I buy?
MS 660 setups commonly use 3/8-inch standard-pitch chain and .063-inch bar gauge. Read the bar stamp and confirm the chain’s pitch, gauge, and required drive-link count before buying.
How can I tell if the chain brake works?
Inspect that the brake is present and undamaged, then follow the manual’s safe functional test. Do not use the saw if the brake fails, is missing, or cannot be checked safely.
Is a long bar a reason to buy a particular used saw?
No. Match the bar to the wood, compatible chain system, and your ability to control the saw. A longer bar does not make a cut safe or prove the saw is in good condition.
What engine speed should the saw have?
Factory reference values are about 2,500 rpm at idle and 13,500 rpm maximum. Confirm them in the applicable manual and use a tachometer for tuning; do not adjust the high-speed screw by ear.
What depth-gauge setting should I use?
For applicable Stihl 3/8-inch chain, a typical setting is 0.65 mm (0.0256 in). Check the chain maker’s specification and use the correct gauge tool.
Should I buy an MS 660 that starts but has a faulty brake?
No. Do not operate it until the brake is repaired and checked. Include the repair and any other unknown faults in your purchase decision.
Is the MS 660 suitable for occasional small branches?
It is a large saw intended for demanding work, not casual pruning. If your jobs are mostly small branches, consider whether a smaller, more suitable saw better matches your workload.
(This article was written by one of our staff writers, Marcus Thorne. Visit our Meet the Team page.)
