Stihl MS 661 Wet vs. Dry Weight (Benchmark)
The STIHL MS 661 powerhead weighs 7.4 kg (16.3 lb) without its bar, chain, fuel, or bar oil. With both tanks full, the powerhead alone is about 8.3 kg (18.3 lb), based on nominal tank capacities and approximate liquid densities. That is an estimate, not a scale-verified wet weight; the complete saw weighs more.
If you have several saws open in browser tabs, the word “weight” can make the comparison harder, not easier. One listing may give powerhead weight; another may describe a complete saw. Those figures are not like-for-like. Here, I separate the published MS 661 figure from a clearly defined fueled weight, then show how to get the number that matters for your bar-and-chain setup.
Equipment Setup, Weight Benchmark & Safety Preparation
This section defines the baseline: STIHL’s 7.4 kg figure describes the powerhead alone, while an equipped, fueled saw includes more parts and liquids. Because bar, chain, fuel, and oil vary, “wet weight” is a setup-specific measurement, not one fixed MS 661 specification.
What STIHL’s 7.4 kg figure includes
The published powerhead weight is 7.4 kg (16.3 lb). It excludes the guide bar, chain, fuel, and bar oil. So it is useful for comparing powerheads, but it does not tell you what you will lift or carry with a working setup.
For scale, the MS 661 has a displacement of 91.1 cm³ and rated power of 5.4 kW (7.2 bhp). Those figures describe engine size and output, not the saw’s complete operating weight. A longer or heavier bar-and-chain combination adds weight and changes balance.
What “wet weight” means here
I use “wet powerhead weight” to mean the powerhead with its fuel and chain-oil tanks filled, but still without the bar and chain. “Ready-to-cut weight” means the complete saw, including bar, chain, fuel, and bar oil. Naming what is included avoids a misleading comparison.
The fuel tank holds 0.825 L, and the chain-oil tank holds 0.36 L. Using approximate densities of about 0.62 kg/L for gasoline and 0.9 kg/L for bar oil, full tanks add roughly 0.84 kg (1.85 lb). That puts the powerhead at about 8.3 kg (18.3 lb) before the bar and chain.
This is an estimate. Liquid density varies, and a tank filled to capacity is not the same as a measured field condition. The reliable way to know your complete setup’s weight is to weigh that setup.
| Benchmark | What is included | Weight |
|---|---|---|
| Published powerhead | Powerhead only; no bar, chain, fuel, or bar oil | 7.4 kg (16.3 lb) |
| Estimated full powerhead | Powerhead plus nominal full fuel and oil tanks; no bar or chain | About 8.3 kg (18.3 lb) |
| Ready-to-cut setup | Powerhead, bar, chain, fuel, and bar oil | Measure your specific setup |
How to measure your actual saw
For a fair comparison, use a scale and write down the setup. Weigh the saw with the bar and chain fitted, then note whether the fuel and oil tanks are full, partly full, or empty. Use the same condition when comparing another saw.
I would record the bar’s length and model, chain specification, and tank condition beside the result. Bar length alone does not give the bar’s weight, and two bars of the same nominal length may differ. Do not add an unverified bar-and-chain estimate to the 7.4 kg powerhead figure and present the total as a measured weight.
A practical record could look like this:
| Your weighing record | Entry |
|---|---|
| Powerhead model | MS 661 |
| Bar length and model | Record from bar markings |
| Chain pitch and gauge | Record from chain/bar markings |
| Fuel condition | Full, partial, or empty |
| Bar-oil condition | Full, partial, or empty |
| Scale reading | Record the measured total |
Takeaway: 7.4 kg is the bare powerhead benchmark. About 8.3 kg is an estimated full-tank powerhead weight. Your complete saw needs a separate measurement.
Field Cutting Operation and Bar/Application Matching
This section connects weight to the work without treating engine size as the only measure of suitability. The MS 661 is a professional, high-output saw intended for large timber and trained operators. Choose a bar and chain that suit the task, your control, and STIHL’s approved fitment information.
Bar and chain affect the number you carry
The MS 661 is commonly configured with a 3/8-inch pitch chain and .063-inch (1.6 mm) gauge. These are not enough to confirm that every bar or chain will fit. Check the bar markings and STIHL’s fitment chart for the exact bar, chain, and drive-link count.
A longer bar can add reach, but it also changes the complete saw’s weight and leverage. That affects how the saw feels during handling. Do not assume that the longest bar is the best choice just because the engine has 91.1 cm³ displacement. Match the bar to the wood, cutting method, and an approved configuration.
| Buying or weighing situation | What the weight tells you | What to verify |
|---|---|---|
| Comparing bare powerheads | The 7.4 kg figure is a useful baseline | Confirm both listings exclude the same parts |
| Planning a fueled saw | Full tanks add about 0.9 kg by estimate | Actual fuel and oil levels |
| Choosing between bar setups | The complete weight and balance will change | Bar model, chain, and fitment |
| Comparing complete saws | A scale reading reflects the actual setup | Same tank condition and included parts |
Safe handling matters to the weight comparison
A number on a product page cannot show how a particular saw feels to you in use. Before cutting, inspect the chain brake, throttle lockout, chain catcher, handles, bar, chain tension, and chain lubrication. Wear a helmet, eye and face protection, hearing protection, chainsaw-resistant leg protection, and suitable boots and gloves.
Plan escape routes and keep bystanders outside the work area. Check the tree’s lean, wind, overhead hazards, and footing. Follow applicable ANSI Z133 requirements and OSHA 29 CFR 1910.266 where they apply to the work. A powerful saw with a longer bar calls for sound training and control, not just strength.
Upper-quadrant contact at the bar tip can cause rotational kickback, which can drive the saw toward the operator. Keep the nose clear of unintended contact, avoid plunge cuts unless trained and equipped for that method, and keep the chain brake in working order. Added reach also changes leverage and handling demands.
Fuel and start checks
The specified fuel mix is 50:1 gasoline to STIHL two-stroke oil. Confirm the fuel is fresh and mixed correctly, and fill the bar-oil tank with suitable chain oil. Start the saw on stable ground using the model’s manual procedure, with the chain brake engaged.
Check that lubrication and brake function are working, then allow the saw to warm before loaded cutting. Do not tune or bypass M-Tronic controls outside STIHL’s prescribed service procedure. The manual is the source for model-specific start, service, and operating instructions.
Takeaway: Choose the bar for the job and your ability to control the saw. Then weigh that exact configuration; the powerhead figure cannot predict its ready-to-cut weight.
Maintenance, Chain Sharpening & Manufacturer-Specified Tuning
This section covers checks that help keep the saw operating as intended and preserve a useful weight benchmark. A clean, correctly maintained saw still has the same basic components, but oil and fuel levels change its measured weight. Use the model manual and chain-maker specifications for service details.
Chain condition and service limits
A dull chain can make cutting harder and may lead an operator to apply more force. Do not force it through wood. Keep it sharp according to the chain manufacturer’s instructions, and use the specified raker setting for that chain; there is no single clearance that applies to every chain.
The MS 661’s approximate engine speed is 2,800 rpm at idle and 9,500 rpm at maximum power. These figures are not a tuning guide. Use the model-specific manual for service limits and electronic-management procedures, and refer service work to a qualified technician when needed.
Check the bar groove, oil passages, chain, and sprocket for wear or blockage. Chain-oil delivery varies with operating conditions and the adjustable-pump setting, so there is no single fixed flow rate that applies in every use. Confirm oil delivery as the manual directs rather than relying on a guessed rate.
Keep weigh-ins comparable
If you track weight over time, record tank levels and setup each time. A scale reading taken with empty tanks cannot be compared directly with one taken after refueling. Likewise, a bar or chain change alters the total even when the powerhead is unchanged.
A simple log can separate a real equipment change from a change in fill level:
- Record the bar and chain fitted.
- Note fuel and bar-oil levels.
- Weigh the complete saw on the same scale when possible.
- Record the date and any changed parts.
Takeaway: Maintenance affects safe function; tank levels and fitted parts affect the scale reading. Record both when comparing weights.
Shutdown, Cleaning & Seasonal Storage
This section describes how to end a work session and prepare for the next one without confusing service needs with the weight benchmark. The saw’s measured weight depends on what remains fitted and how much fuel and oil it holds. Follow the operator’s manual for storage and service steps.
Engage the chain brake, shut the saw down, and let it cool. Clean around the air-filter area and sprocket cover, and clear the bar groove and oil passages as directed. Inspect the chain, bar rails, and sprocket. Retension only when it is safe and in line with the manual.
Refuel only after the saw has cooled and away from ignition sources. For storage, follow STIHL’s instructions for the model and fuel system; do not assume that a tank should be left full or emptied without checking the manual. If you weigh the saw after service, note any fuel or oil removed so the result remains clear.
Takeaway: For a useful post-service weight, record the fitted bar and chain and the remaining fuel and oil. A changed reading may reflect the fill level, not a change in the powerhead.
Frequently Asked Questions
These answers distinguish published powerhead weight from estimated or measured complete-saw weight. The key is to state what is included each time. For a specific bar-and-chain setup, use a scale and verify parts against STIHL fitment information.
What is the STIHL MS 661 powerhead weight?
The published powerhead weight is 7.4 kg (16.3 lb), without the bar, chain, fuel, or bar oil.
What is the estimated weight with full fuel and bar oil?
The powerhead is about 8.3 kg (18.3 lb) with nominally full tanks, before adding the bar and chain. This is an estimate, not a scale-verified specification.
Does STIHL publish one fixed wet weight for the MS 661?
No single wet weight applies to every setup. Fuel, bar oil, guide bar, and chain change the total.
Is 7.4 kg the weight of the saw ready to cut?
No. It is the powerhead figure. A ready-to-cut weight also includes the fitted bar and chain, plus fuel and bar oil.
How much do the bar and chain add?
There is no one verified amount for every configuration. Their weight depends on the exact bar and chain, so weigh your fitted setup.
What chain pitch and gauge are common on the MS 661?
A common configuration is 3/8-inch pitch and .063-inch (1.6 mm) gauge. Confirm the exact fit, including drive-link count, from the bar markings and STIHL’s fitment chart.
Does a longer bar make the saw heavier?
A longer bar can change the complete saw’s weight and balance. The amount depends on the exact bar and chain; check the parts or weigh the assembled saw.
Can I compare the MS 661’s 7.4 kg figure with another saw’s fueled weight?
Not fairly unless you first put both figures on the same basis. Compare powerhead with powerhead, or weigh both complete saws with the same parts and tank conditions.
How should I weigh my MS 661 for a buying comparison?
Fit the bar and chain you plan to use, set and record fuel and oil levels, then weigh the complete saw. Record the configuration beside the result.
What is the clearest benchmark to use when shopping?
Use 7.4 kg (16.3 lb) for the MS 661 powerhead baseline. Treat about 8.3 kg (18.3 lb) as an estimated full-tank powerhead figure, then measure the complete setup you intend to operate.
(This article was written by one of our staff writers, Marcus Thorne. Visit our Meet the Team page.)
