Stihl 066 vs. MS 660 vs. MS 661 (Field Comparison)
The 066, MS 660, and MS 661 are all large professional saws, but they are not identical. The 066 and MS 660 share a 91.6 cm³ displacement; the MS 661 is 91.1 cm³ and has a stated maximum power of 5.4 kW. Compare the exact model, condition, manual, and service support before buying.
The name on the cover does not tell you everything about a used saw. A clean MS 660 may be a better buy than a worn MS 661, while an old 066 may need model-specific parts or service. I compare these saws by what matters in the field: power, controls, fit, condition, and whether you can support the machine over time.
One point needs care: the 066’s specifications can vary by version and market. Do not treat every 066 as an MS 660 with a different badge. Check the model plate and use the matching STIHL manual before setting up or tuning the saw.
How the 066, MS 660, and MS 661 differ
These are large-displacement professional saws intended for demanding work by trained users. Their capacities are close, but the MS 661 has a small power advantage in the listed specifications, and the 066’s version-specific details make its exact comparison dependent on identification.
| Model | Displacement | Maximum engine power | Field comparison |
|---|---|---|---|
| 066 | 91.6 cm³ | Varies by version and market | Identify the exact version; consult its manual |
| MS 660 | 91.6 cm³ | 5.2 kW | Closely related in displacement to the 066 |
| MS 661 | 91.1 cm³ | 5.4 kW | Slightly smaller displacement, higher listed power |
Displacement is the volume swept by the piston as it moves through the cylinder. It is useful for comparing engine size, but it does not predict cutting speed on its own. Chain sharpness, wood, bar setup, engine health, and operator technique all affect the cut.
The MS 661’s listed power is 0.2 kW above the MS 660’s. That is a specification difference, not a promise that every 661 will outcut every 660. A poorly tuned or worn saw can give up its advantage.
What the model names can and cannot tell you
A model name points to a product family, not the saw’s present condition or exact configuration. I start with the model identification, then check the serial marking, parts, and manual. On an older saw, a replaced cover or mixed parts can make a visual check misleading.
STIHL has used different versions and specifications across markets. Therefore, do not infer production year or exact specification from a seller’s description alone. Ask for clear photographs of the identification markings and compare them with STIHL’s records or a knowledgeable authorized dealer. A serial number is a verification lead, not proof that the saw is genuine.
Which one makes sense for your work?
The best choice depends on the wood, the saw’s condition, and your ability to get parts and service. All three can suit demanding bucking and trained-user felling. Bar length should follow the job and your control, not the displacement figure or a seller’s claim that a longer bar proves a saw is “more professional.”
A 25–36 inch bar is a practical range for many jobs, but it is not a universal fit recommendation. Longer bars add weight and leverage and increase kickback exposure. Confirm the exact bar and chain combination, including the approved limits, in the manual for that saw.
| Your priority | What to consider | Buying or setup check |
|---|---|---|
| Regular heavy cutting | The MS 660 and MS 661 have published power figures; the 661’s is higher | Compare running condition and service history |
| An older, lower-cost saw | An 066 may be suitable if its exact version is identified | Confirm parts availability and manual before purchase |
| Long-bar work | Bar length must suit wood, method, and operator control | Check bar limits and chain match in the manual |
| Low-risk ownership | Dealer support can matter as much as the model | Call a local STIHL dealer about service and parts |
| Used purchase | Condition can outweigh small specification differences | Arrange an inspection or compression and operating check by a qualified technician |
In a practical buying comparison, I would put two saws side by side and inspect them in this order: identity, safety parts, bar and chain match, cold start, idle, oiling, and cutting behavior. This is an inspection sequence, not a substitute for a technician’s diagnosis. If the seller will not allow basic checks, price the uncertainty into the decision or walk away.
Equipment Setup and Safety Preparation
Setup means confirming that the saw, cutting attachment, and safety parts match before the engine starts. These high-power saws can cause severe injury. Wear suitable chainsaw protective equipment, secure the work area, and use trained help when the tree or cutting plan is beyond your ability.
First, identify the exact model and find its manual. Check the chain brake, throttle lockout, chain catcher, handles, bar nuts, and chain tension. Match the chain to the bar and sprocket by pitch, gauge, and drive-link count. The common pitch is 3/8 inch, but that does not make every chain interchangeable.
Chain gauge is the thickness of the drive link that sits in the bar groove. A .050-inch chain and a .063-inch chain are not interchangeable: the chain must match the bar groove, as well as the pitch and drive-link count. Check the markings on the bar and the chain before fitting parts.
Plan the work before starting. Establish an exclusion zone and escape routes. For felling, assess lean, defects, wind, targets, and overhead hazards. If you cannot control the plan, stop and get qualified help.
Start on stable ground with the chain brake engaged and the chain clear of people and objects. Follow the saw’s cold- or warm-start procedure. Confirm that the chain stays still at idle and that lubrication works using the test described in the manual. Do not begin cutting if either check fails.
Field Cutting and Landscaping Operation
Field use is where model condition and setup meet operator skill. Keep a two-handed grip and stable footing. Use the lower part of the bar where practical, and keep the upper bar nose away from wood and obstructions; nose contact can trigger rapid rotational kickback.
Kickback is a fast upward and backward movement that can happen if the upper quadrant of the bar nose contacts an object. The chain brake can reduce the consequences, but it does not make kickback safe. Do not cut one-handed, and do not rely on the brake as permission to work near the bar nose.
Use wedges and a suitable bucking sequence to manage pinching. For felling, use a planned notch and hinge suited to the tree and method. Do not improvise dimensions or attempt a fall beyond your training. Stop if the tree shifts, the saw binds, or the conditions no longer match your plan.
Field decision examples
These examples show how I would apply the comparison; they are not reports of a specific job or a guarantee of performance. The point is to choose based on the task and the individual saw, not just the badge.
- A buyer choosing between an MS 660 and MS 661: If both are in sound condition, compare the 661’s higher listed maximum power with the actual service record, controls, and dealer support. A specification alone does not settle the choice.
- A used 066 with an uncertain history: Verify its version and manual before ordering parts or setting it up. If model identity or engine condition remains unclear, have a qualified STIHL service provider inspect it.
- A long-bar setup for large wood: Confirm the bar is approved for the exact saw and that the chain matches. If a shorter bar can do the work safely, it may offer better control and less leverage.
Maintenance, Chain Sharpening, and Tuning
Maintenance keeps a professional saw working as designed, but adjustment values are not shared across all three models. Use the correct manual and chain-maker guidance for the exact saw and cutting equipment. Do not copy an idle speed, maximum RPM, depth-gauge setting, or oil-flow rate from another model.
Use fresh, correctly prepared fuel. STIHL specifies a 50:1 mix with suitable gasoline and STIHL two-stroke oil for these saws; confirm the instructions for the exact saw and oil. Incorrect fuel preparation can damage a two-stroke engine. Do not guess at the mix or use stale fuel.
A sharp chain should cut without forcing the saw through the wood. Follow the chain manufacturer’s filing and depth-gauge specifications. The depth gauge, sometimes called a raker, controls how much wood each cutter takes. Its correct setting depends on the chain type, so one clearance should not be applied to every chain.
Set idle and maximum engine speed with a tachometer, using the applicable manual and a qualified technician when needed. Chain type, bar, temperature, and serial or version differences can affect service settings. If the saw idles with the chain moving, fails to oil, or behaves unusually, stop and correct the problem before cutting.
Shutdown, Storage, and Seasonal Care
A safe shutdown prevents injuries during cleanup and helps protect the saw between jobs. Engage the chain brake, stop the engine before adjusting the chain or clearing debris, and let the saw cool. Then inspect the cutting parts and clean the areas specified in the manual.
Check the chain, bar, and sprocket for wear or damage. Clean the air intake and cooling fins as directed so debris does not block airflow. Handle and store fuel according to the manual and local requirements. If the saw will sit for a long period, follow STIHL’s storage instructions for that model rather than relying on a general rule.
Which saw should you choose?
Choose by verified condition and support first, then by the specifications that fit your work. The MS 661 has the highest listed maximum power of the three in the figures above. The MS 660 shares the 066’s listed displacement, while an 066 needs closer version checks. None is automatically the best buy without inspection.
Before committing, confirm the model and serial marking with STIHL or an authorized dealer, check that the parts match the manual, and ask who can service the saw locally. A genuine, well-maintained saw with a compatible bar and chain is a safer choice than a more impressive model name with unknown history.
Frequently asked questions
Is the 066 the same saw as the MS 660?
No. They share a listed displacement of 91.6 cm³, but 066 specifications can vary by version and market. Verify the exact saw and use its model-specific manual.
Is the MS 661 more powerful than the MS 660?
The listed maximum engine power is 5.4 kW for the MS 661 and 5.2 kW for the MS 660. Actual cutting results also depend on condition, chain sharpness, setup, wood, and technique.
Which has the largest displacement?
The 066 and MS 660 are listed at 91.6 cm³. The MS 661 is listed at 91.1 cm³.
What bar length should I use?
Choose a bar for the tree, cutting method, and your control. A 25–36 inch bar is practical for many jobs, but check the exact saw manual before fitting one. Longer bars increase weight, leverage, and kickback exposure.
Do these saws use a 3/8-inch chain?
That pitch is common, but the correct chain must also match the bar’s gauge and drive-link count, plus the sprocket. Check the parts on the saw and the manual rather than assuming fit.
Can I use .050-inch and .063-inch chain on the same bar?
No. The chain gauge must match the bar groove. Those gauges are not interchangeable.
What fuel mix should I use?
STIHL specifies 50:1 with suitable gasoline and STIHL two-stroke oil for these saws. Confirm the instructions for the exact saw and oil, and use fresh, correctly prepared fuel.
Can I use an MS 660 tuning setting on an 066?
Do not assume so. Idle and maximum-speed settings are model- and condition-specific. Use the applicable manual and a tachometer, with qualified service help when needed.
How can I verify a used saw’s serial number?
Record the markings and ask STIHL or an authorized dealer to help confirm the model and service information. Treat a serial number as one check, not proof by itself that a saw is genuine.
Which model is best for a used-saw buyer?
There is no best choice based on the badge alone. Verify identity, condition, compatible parts, and local service support before comparing price or power figures.
(This article was written by one of our staff writers, Elliott Fowler. Visit our Meet the Team page.)
