Stihl FS 55 R Performance (Power & Specs Guide)
The STIHL FS 55 R is a 27.2 cm³, two-stroke trimmer rated at 0.75 kW (1.0 bhp). Its loop handle suits trimming and maneuvering in grass, while its cutting ability depends on the approved head or blade, guard, and manual for your exact machine. Use fresh 50:1 fuel mix, keep the unit maintained, and stop if it runs unusually hot or vibrates.
When a trimmer will not start just as the grass takes off, it can turn a simple yard job into a costly delay. I check the basics first: the fuel mix, air filter, cutting attachment, and the machine’s own instructions. That routine matters with the FS 55 R because a small fuel or setup problem can affect both starting and performance.
FS 55 R specifications and what they mean
These figures give a practical baseline for identifying the machine and setting expectations. Engine output is not a promise of a fixed cutting rate: the result also depends on the vegetation, attachment, line condition, and operator technique. Use the manual for your exact unit whenever its details differ from this guide.
| Specification | Common North American figure | Practical meaning |
|---|---|---|
| Engine displacement | 27.2 cm³ | The engine’s cylinder size |
| Rated output | 0.75 kW (1.0 bhp) | The stated engine power |
| Engine type | Single-cylinder, two-stroke | Requires the specified gasoline-and-oil mix |
| Fuel mix | 50:1 gasoline to STIHL two-stroke oil | For example, 5 L gasoline plus 100 mL oil |
| Fuel-tank capacity | 0.33 L | The tank’s stated volume, not a guaranteed run time |
| Weight | 4.4 kg (9.7 lb) | Excludes fuel, cutting attachment, and deflector |
| Handle style | Loop handle | Allows close control and maneuvering |
Displacement measures the space inside the cylinder as the piston moves. Rated output describes the engine’s stated power, but it does not tell you how quickly every type of grass will be cut. Thick, wet growth and a worn or unsuitable line can slow the job.
The weight figure is also not the ready-to-use weight. Fuel and the fitted cutting parts add weight, so consider the complete machine when judging comfort. The loop handle is suited to trimming and maneuvering; it does not make the FS 55 R suitable for work beyond the approved attachment’s rating.
What the FS 55 R can cut
The FS 55 R is a line trimmer and brushcutter for light grass, edging, and vegetation that the approved cutting attachment can handle. Attachment compatibility is specific: use only a combination of cutting tool, deflector, and handle configuration allowed by your machine’s manual. Do not treat the engine’s power rating as permission to fit an unapproved tool.
A line head is generally used for grass and trimming around yard edges. A blade may be allowed for some vegetation, but only when the manual approves that blade and the matching guard. The exact cutting method and limits depend on the fitted tool and the manufacturer’s instructions.
| Yard task | What to check | Performance expectation |
|---|---|---|
| Light grass trimming | Correct line head, line type, and guard | Appropriate for routine grass work |
| Edge cleanup | Approved head and controlled handling | Useful for detail work; avoid forcing the head |
| Heavier vegetation | Whether a listed blade and guard are approved | Stay within the attachment’s stated limits |
| Work beyond the approved tool’s rating | Do not proceed with the FS 55 R setup | Choose equipment designed for that work |
An attachment must match the machine, not just fit onto the shaft. The correct guard helps protect you from contact and thrown debris. Check the manual for approved parts and configurations, and stop if you cannot confirm a tool is suitable.
Setup and safety before trimming
Safe setup means checking the machine before starting, then keeping the right protection and distance while it runs. A secure attachment and correct guard are as important as a sound engine. If a part is loose, damaged, or mismatched, do not start work until the issue is corrected.
Before each use, inspect:
- Throttle trigger and interlock, stop switch, handles, and harness, if fitted.
- Shaft, attachment retention, cutting head or blade, and guard.
- Fuel lines for visible damage or leakage.
- The guard for a correct match to the fitted cutting attachment.
Wear eye or face protection, hearing protection, gloves, long trousers, and sturdy footwear. Keep people and animals away from the work area. At least 15 m (50 ft) is a common STIHL brushcutter exclusion distance, but follow the distance and other safety directions in your exact manual.
Keep the guard between you and the cutting attachment. Never clear a jam or adjust the attachment while the engine is running. If you notice fuel leaking, abnormal vibration, damaged cutting parts, or loose hardware, switch off and wait for the attachment to stop before inspecting it.
Starting and trimming for steady performance
A good start follows the control positions in the manual rather than a guessed sequence. Starting steps can differ with engine temperature and control design. Set the machine on stable ground, keep the cutting attachment clear, and secure the unit before pulling the starter. Never start it while carrying it.
For a cold start, set the controls and choke as the manual directs, then pull the starter until the engine fires. Move the control to the run or warm-up position as directed and let the engine stabilize. For a warm start, use the manual’s warm-start procedure. Keep hands and feet clear of the attachment during both procedures.
When trimming with a line head, use controlled throttle and sweep from side to side without forcing the head into the grass. A dull, short, or incorrect line can make work less effective; use the line type and diameter specified for the fitted head. If using an approved blade, follow its specific cutting instructions rather than using the line-head technique.
Stop at once if the machine vibrates abnormally, loses power, overheats, leaks fuel, or the attachment is damaged or jammed. Let the attachment stop fully before you inspect it. Continuing through a warning sign can turn a small fault into major engine or injury risk.
Maintenance and seasonal storage
Routine care helps the engine start and run as intended, but it cannot make an unsuitable attachment safe or fix internal damage. Follow the FS 55 R manual for service intervals, fuel-system steps, spark-plug details, and carburetor settings. Do not guess at mixture-screw positions or tune to an assumed engine speed.
Keep the air filter, cooling-air inlets, cutting-attachment guard, and spark-arresting screen clean if one is fitted. Inspect the fuel lines and attachment before use. Use fresh, correctly mixed fuel and the spark plug specified for the model. Clean or service the filter and plug as instructed in the manual.
For line replacement, use the diameter and type specified for the head. Check blades for cracks, bends, and correct sharpening; do not run a damaged or unbalanced blade. If the engine is hard to start, accelerates poorly, overheats, idles abnormally, or spins the attachment at idle, have a qualified STIHL service dealer inspect it.
For extended storage, follow the manual’s fuel-system procedure and do not leave stale premix in the machine. Keep fuel in an approved, labeled container away from ignition sources. Clean and inspect the trimmer, store it dry with the attachment protected and out of children’s reach, and secure it with the engine stopped during transport.
A lean-running two-stroke engine can overheat quickly and suffer piston or cylinder seizure. Stale or incorrectly mixed fuel, a restricted fuel line or filter, or an air leak can contribute to this condition. If the engine surges, loses power, or runs unusually hot, stop using it and address the fuel-supply problem or seek service. Do not keep running it at full throttle to test it.
Practical field checks for common problems
These examples are diagnostic situations, not reports of specific customer repairs. They show how I separate an operating issue from an engine fault without guessing at a carburetor adjustment.
The trimmer starts, then loses power: I first stop the engine and check for an obstructed air filter, dirty cooling-air inlets, old fuel, or a cutting attachment burdened by vegetation. I compare the fuel mix and attachment against the manual. If the problem persists or the engine runs hot, I stop and arrange service rather than continuing.
The engine runs, but trimming feels weak: I check that the line head has the specified line and that the line is in usable condition. I also confirm the guard and attachment are correct. If the unit still accelerates poorly or cannot maintain normal operation, that may point to a service issue rather than a need to force the cutting head.
The machine vibrates after a tool change: I switch it off and wait for the attachment to stop. Then I inspect the tool and retention parts for damage, looseness, or incorrect fit. I do not resume until the manual confirms the setup and the parts are secure; a damaged or unbalanced blade must not be used.
The key step in each case is to stop before inspecting. That protects you and avoids turning a simple check into contact with a moving attachment.
Frequently asked questions
These short answers cover common questions about FS 55 R power, fuel, attachments, and care. Exact fitment and service details can vary, so use your machine’s manual and nameplate to confirm specifications before maintenance or part selection.
How much power does the STIHL FS 55 R have?
Its common North American rated output is 0.75 kW, or 1.0 bhp. Check the nameplate or manual for your version.
What is the engine size?
The common specification is a 27.2 cm³, single-cylinder, two-stroke engine.
What fuel mix does the FS 55 R use?
Use a 50:1 gasoline-to-STIHL two-stroke oil mix. One example is 5 L gasoline with 100 mL oil.
How much fuel does the tank hold?
The common North American tank capacity is 0.33 L. That figure does not establish a guaranteed run time.
How heavy is the FS 55 R?
The stated machine weight is 4.4 kg (9.7 lb), excluding fuel, cutting attachment, and deflector.
Is the loop-handle FS 55 R suitable for light grass?
Yes, when fitted with the approved cutting head and guard. Follow the manual for the correct line and operating method.
Can I fit a blade to an FS 55 R?
Only if the blade, guard, and handle configuration are approved for your exact machine in its manual. Do not rely on physical fit alone.
Why does my FS 55 R lose power or run hot?
Possible causes include restricted airflow, stale or incorrectly mixed fuel, a fuel-supply restriction, or an air leak. Stop using it if it runs unusually hot and seek service if basic checks do not resolve the problem.
What should I check if it vibrates?
Stop the engine and wait for the attachment to stop. Inspect the attachment and retaining parts for damage, looseness, or incorrect fit before restarting.
Should I adjust the carburetor myself?
Do not set the mixture screws by guesswork or tune to an assumed RPM. Follow the manual; have a qualified STIHL service dealer address persistent running or idle problems.
(This article was written by one of our staff writers, Harrison Croft. Visit our Meet the Team page.)
