FS 91

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A professional bike-handle trimmer with simplified starting, improved air filtration and 30% longer run time than the FS 90.

Product Description

If you’re a landscaping professional who uses their trimmer for mowing applications, grab the powerful STIHL FS 91 trimmer. Its bike-handle design adds greater comfort and leverage, thanks to its redesigned rubberized grips. The trimmer also features one touch stop and a simplified starting procedure enabled by the semi-automatic choke lever. Its low-emission engine is paired with a larger fuel tank, delivering 30% longer run times when compared to the FS 90. The engine also includes improved air filtration and STIHL exclusive IntelliCarb™ technology for maximum RPM. And when the terrain gets tough, this trimmer’s solid steel drive shaft accepts a wide range of heavy-duty cutting heads, including metal blades, for maximum versatility.

Model Features

  • Reduced-Emission Engine Technology - Caring for Nature
    The STIHL Inc. “Caring for Nature” seal identifies its powered products that are more environmentally conscious, producing zero or low exhaust emissions. STIHL Inc. defines “low exhaust emissions” as being cleaner than EPA and/or CARB exhaust emission standards.

    More information

  • Built in the USA
    Indicates products that are built in the United States from domestic and foreign parts and components.

    More information

  • Cutting Heads & Blades Selection Chart
    Need help selecting a cutting head or blade for your STIHL trimmer or brushcutter?

    Click here to view the Cutting Heads & Blades Selection Chart (PDF Format).
  • Loop Handle (R)
    Loop handle grass trimmers and brushcutters are ideal for trimming between bushes and shrubs and other areas where space is limited.
  • Bike Handle
    When used in conjunction with a harness, the bike handle allows the machine to be easily guided, enabling a smooth horizontal mowing action to cover large areas quickly and efficiently. With soft grips for increased comfort, the bike handle provides greater control and helps reduce operator fatigue.

    See it in action!
  • Shoulder Strap / Carrying System
    Using a shoulder strap or carrying system helps distribute the weight of the equipment for increased operator comfort and improved maneuverability.
  • Multi-Function Control Handle
    Having easy access to all of the controls on one comfortable handle makes it easy to complete tasks so the operator’s hand never has to leave the handle.
  • IntelliCarb™ Compensating Carburetor
    The IntelliCarb™ Compensating Carburetor measures the air pressure on the clean side of the air filter and adjusts the metering diaphragm in the carburetor. This keeps the RPM at a consistent level, even when the air filter begins to clog.
  • Tool-Free Handle Adjustment
    The central wing nut enables easy adjustment without the use of tools. For transportation and space-saving storage, the handle can be rotated 90°.
  • Purge Pump Primer
    By pressing the bulb, this small fuel pump delivers fuel to the carburetor, reducing the number of starting pulls needed after an extended break between uses.
  • Anti-Vibration System
    STIHL has a system for minimizing the vibration levels of handheld outdoor power equipment. The STIHL anti-vibration system helps reduce operator fatigue and provides a more comfortable working experience.
  • Upright Translucent Fuel Tank
    Allows operator to easily check fuel level before starting work. Upright position makes it easier to refill.
  • Protected Spark Arrestor Muffler
    Has large baffles which reduce noise level and contains a screen designed to reduce the emission of sparks.
  • Protected Spark Plug
    Protected yet easy to change.
  • Simplified Starting Procedure
    To get started, simply pump the fuel primer, set the choke and pull the starter cord. The built-in stop switch allows the user to turn off the engine with a simple press of the button. When the engine is off, the throttle lock automatically returns to the “start” setting. Your power tool will be ready to be started when you’re ready to get back to work.

    See it in action!
  • Heavy-Duty Steel-On-Steel Clutch
    Centrifugal clutch is designed to reduce slippage.
  • Protected or Enclosed Control Cables
    Eliminate dangling and loose wires.
  • Air Filter Cover
    Easily removed for fast and easy filter cleaning or replacement.
  • Throttle Trigger Interlock
    Must be depressed before the trigger can be activated.
  • Protected Choke Lever/Knob
    Helps prevent damage.
  • High Tech Polymer Housing
    Housings are lightweight, withstand greater impact and are corrosion-resistant.
  • Fully Lined Drive Shaft
    Provides smooth operation and less vibration.

Specifications

DISPLACEMENT
28.4 cc (1.73 cu. in.)
ENGINE POWER
0.95 kW (1.27 bhp)
WEIGHT*
5.8 kg (12.8 lbs.)*
FUEL CAPACITY
710 cc (24.0 oz.)
CUTTING SWATH
16.5"
POWER SOURCE
Gas
*Without deflector and cutting attachment.

Important Information

WARNING! Improper use of any trimmer/brushcutter can cause serious or fatal injury. Read, understand and follow all safety instructions in your instruction manual. To reduce the risk of injury from blade contact, circular saw blades may be used on FS brushcutters that have a limitstop, a bicycle handle and double shoulder harness and not on FS brushcutters with a "J" handle or loop handle. Other rigid blades may be used on FS brushcutters having a bicycle handle, a "J" handle or a loop handle equipped with a barrier bar. To reduce the risk of eye injury always wear proper eye protection. Always use the appropriate deflector for the type of cutting attachment, as explained in your instruction manual.

Note: STIHL engine products with the Caring for Nature logo are cleaner than EPA Standards for exhaust emissions.

Note: STIHL recommends use of fuel with no more than 10% Ethanol content. Using fuel with greater than 10% Ethanol content may cause damage to your equipment and may void your STIHL warranty. Learn More…

WARNING! Improper use of any power tool may cause serious or fatal injury. Read, understand and follow carefully the operating and safety instructions in your instruction manual before using such products.

STIHL products sold through U.S. STIHL Dealers are for distribution in the United States only.

Reviews

FS 91 is rated 4.3 out of 5 by 58.
Rated 5 out of 5 by from Good buy Using the three sided blade with this makes short work of even 1” stocks/trunks. Does a great job. My only issue is that the spacer between the blade and assembly bolt wore out and flew off the first day of use. I did however clear a half acre of thick,tall weeds on top of gravel and steel slag. I still,use it. Keeps on cutting
Date published: 2019-09-13
Rated 4 out of 5 by from Nice balance, comfortable to use, decent power. Bicycle handles are the way to go! Along with the double shoulder harness, I can use this all day. Power is good, cut through everything I've thrown at it.
Date published: 2019-09-12
Rated 3 out of 5 by from Lack of power We use the FS 91 for mowing prairies. We were expecting the new FS 91 we bought to have the same capabilities as the other ones but it doesn't. There is a serious lack of power that doesn't compare to the other trimmers of the same model. It runs well but just doesn't get the same job done as the other trimmers. We would have purchased a larger engine if we knew this one was weak in power.
Date published: 2019-09-05
Rated 4 out of 5 by from Great power Ist time purchasing this size of weed eater has great power and gets the job done quick. Starts easy waiting to see after one year if it still starts this good. only complaint is the strap could use some improvement for easy adjustment and comfort. I have to adjust often pending if I am trimming around the pond or up and down a hill side. The machine is worth the money tho
Date published: 2019-08-12
Rated 4 out of 5 by from This product does not work as well as my FS 90 The FS 91 has the same power as my FS 90 but the FS 90 started on the first pull every time for 5 years without fail. My new FS 91 seems to flood out initially every time I go to use it. It is a bit of a nuisance!!
Date published: 2019-08-05
Rated 4 out of 5 by from Replaced an FS90; the -91 has some minor changes I would not have made. Got the FS91 to replace a broken FS90 (a very disappointing thing, autopsy pending). It is too early in the game to rate dependability or quality, above are the first month or so. I don't know why the change in gas cap (clip to thread) or the choke control. The elimination of the ability to lock the throttle open is a minus. All are comparisons to the FS90. I would call those changes unnecessary, but in no way fatal.The FS91 starts easy and runs strong. I have multiple open acres to clear for fire protection each year and when the fire protection folk ban bladed mowers, the FS-90, now -91, is the go-to implement. it performs well.
Date published: 2019-07-22
Rated 5 out of 5 by from Quality build, starts easily First gas trimmer I have owned. Was concerned about starting and trouble with another internal combustion engine. No worries at all. Easy to maintain, starts so easy. 5 hillside acres was neglected for the last few years and had grass weeds 3 - 4 feet high. Cut through them like butter. Large gas tank would require a refill when the string ran out. I use the 4 or 5 sided string and it works great. Bought a circular saw for it to use on brush and saplings. Works good if you don;t put it on upside down!
Date published: 2019-07-17
Rated 5 out of 5 by from Best in show. Well made, strong, powerful, light weight, easy to start. I had 4 different trimmers in 7 years and none can hold a candle to my STIHL. Buy one today. It's the last one you will need to buy. Why did I ever waste my money and time buying cheapies. You get what you pay for.
Date published: 2019-07-16
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Optional Accessories

  • Gearbox Attachments
    Gearbox attachments are available for this model. View the interchangeable gearbox chart to find out which attachments work with this model.
  • Straps and Harnesses
    They distribute the load from your hands to your shoulders. They also help reduce operator fatigue and make it easier to use trimmers, brushcutters and clearing saws for extended periods.
  • Trimmer Line
    There's high-performance STIHL trimmer line for every operating condition. 
  • Trimmer Heads & Blades
    Many trimmer heads and blades are available. Find out which ones to use with this model in this chart.  

Standard Features

  • Common Features for Trimmers
    View the features common to many STIHL trimmers.

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Support

Read what our customers say about STIHL Trimmers
STIHL Trimmers & Edgers, the Right Tools for the Job - Video
How to Wind a STIHL Trimmer Head - Video
Cutting Heads & Blades Selection Chart (PDF)
FS 91 Instruction Manual (PDF)
Download Instructions on How to Rewind Your Trimmer Head (PDF)
Product Safety Manual (PDF)
STIHL Limited Warranty
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