Stihl FS 100 RX Manual

The Stihl FS 100 RX is a professional-grade, straight-shaft grass trimmer/brushcutter designed for demanding clearing and maintenance work. It features a powerful 2-stroke engine with anti-vibration system, ErgoStart™ for easy starting, a robust gearbox, and compatibility with a wide range of cutting heads and blades. Below are key sections for safety, features, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: STIHL 2-MIX engine, ErgoStart™ system, anti-vibration handles, modular shaft, robust gearhead, and quick-stop centrifugal clutch.

Feature	Description
Engine Type	STIHL 2-MIX, single cylinder, 2-stroke
Displacement	31.8 cc
Power Output	1.3 kW / 1.8 hp
Starting System	ErgoStart™ (recoil starter)
Fuel Tank Volume	0.55 liters
Shaft Type	Straight, solid drive shaft
Anti-Vibration System	Integrated into handle and engine mounts
Clutch	Centrifugal, quick-stop
Gearbox	Heavy-duty, serviceable
Weight (without cutting attachment)	Approx. 6.2 kg

Safety Instructions

Read and understand all instructions before use. Always wear appropriate PPE.

1. Personal Protective Equipment (PPE): Always wear safety glasses, hearing protection, sturdy gloves, long pants, and non-slip boots.
2. Work Area Safety: Clear area of bystanders, especially children and pets. Be aware of thrown object hazards.
3. Machine Handling: Hold unit firmly with both hands. Do not operate with one hand. Keep all body parts away from cutting attachment.
4. Fuel Safety: Refuel outdoors only, with engine stopped and cool. Use only STIHL-approved fuel mix.

WARNING! Risk of severe injury or death from blade contact, thrown objects, or fire. Never operate without proper guards and PPE.

Assembly & Preparation

Unpack and inspect contents. Assemble handle, shaft, and cutting attachment.

1. Attach Handle: Slide handle onto shaft at desired position and tighten clamping screws securely.
2. Install Cutting Attachment: Ensure machine is off. Fit the chosen trimmer head or blade, securing with the appropriate nut and washer. Use the STIHL combination wrench.
3. Install Guard: Always install the correct cutting attachment guard (deflector) before operation.
4. Fuel Mix: Prepare fuel: Use high-quality unleaded gasoline (min. 89 octane) mixed with STIHL HP Ultra 2-stroke oil at a 50:1 ratio.

CAUTION! Ensure all fasteners are tight before starting. An improperly secured blade can become a lethal projectile.

Specifications

• Model: FS 100 RX
• Engine: STIHL 2-MIX, air-cooled, single-cylinder two-stroke
• Displacement: 31.8 cm³
• Powerhead Weight: 6.2 kg
• Fuel/Oil Ratio: 50:1 (STIHL HP Ultra oil)
• Fuel Tank Capacity: 0.55 L
• Sound Pressure Level (LpA): 99 dB(A)
• Vibration Level (ah): Left Handle: 4.5 m/s², Right Handle: 6.5 m/s²
• Recommended Cutting Attachments: STIHL AutoCut heads, circular grass blades, brush knives
• Warranty: Limited warranty for professional use. See dealer for terms.

Controls and Components

Main controls located on the handle and engine housing.

Handle Controls: Throttle trigger with lockout, stop switch (I/O), throttle trigger lockout.

Engine Housing: Master control lever (for starting: move to cold start position '⛭'; for run: '⨁'), choke lever, fuel primer bulb, spark plug boot.

Components: Debris shield, shoulder strap attachment points, spark arrestor muffler, gearbox with grease nipple, shaft coupling.

Fuel & Lubrication

Use only clean, fresh fuel mix and proper lubricants.

1. Fuel Mix: Always use 50:1 mix with STIHL HP Ultra oil. Do not use old or stale fuel.
2. Refueling: Clean area around fuel cap. Use a funnel. Do not overfill. Tighten cap securely.
3. Gearbox Grease: Lubricate gearbox regularly with STIHL special grease. Use grease gun on nipple.
4. Air Filter: Clean regularly with soapy water, dry, and re-oil with STIHL filter oil.

Tip: Store fuel in an approved container, away from heat and sparks, for no more than 30 days.

Starting & Operation

1. Starting (Cold Engine):
   • Press fuel primer bulb 5-10 times.
   • Set master control lever to cold start position '⛭'.
   • Place unit on firm ground. Hold handle down with foot. Pull starter cord briskly until engine fires.
   • Move master control lever to run position '⨁'. Pull starter cord to start.
2. Starting (Warm Engine): Master control lever stays in '⨁' position. No choke needed.
3. Operation: Allow engine to warm up at idle for 30 seconds. Use smooth, sweeping motions. Do not "scythe" or swing wildly.
4. Stopping: Release throttle, allow engine to idle briefly, then move stop switch to 'O'.

WARNING! Keep hands and feet away from cutting attachment at all times, especially during starting.

Cutting Attachments

Compatible with various STIHL attachments. Always use correct guard.

Attachment	Best Use	Guard Required
STIHL AutoCut 26-2	Grass, weeds	Deflector D
Circular Grass Blade	Tall grass, light brush	Deflector A or BC
Brush Knife (4-tooth)	Heavy brush, saplings	Deflector BC
PolyCut Head	Finish trimming	Deflector D

Always ensure cutting attachment is properly installed, balanced, and sharp.

Maintenance & Storage

Regular maintenance ensures long life and safe operation.

1. Daily: Clean exterior, check for loose fasteners, inspect cutting attachment for damage.
2. Weekly/AFTER 20 Hrs: Clean air filter, check spark plug, clean cooling fins, grease gearbox.
3. Storage (Short-term): Run carburetor dry or add fuel stabilizer.
4. Storage (Long-term): Drain all fuel. Run engine until it stops. Remove spark plug, add a teaspoon of oil into cylinder, pull starter slowly 2-3 times, reinstall plug. Store in a dry place.

CAUTION! Always disconnect spark plug boot before performing any maintenance.

Warranty Information

This STIHL power tool is covered by a limited warranty for professional/commercial use. Warranty details are provided by your authorized STIHL dealer at the time of purchase. Warranty does not cover damage from misuse, neglect, improper fuel, or unauthorized repairs. Always use genuine STIHL replacement parts.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel, flooded, bad spark, clogged filter	Check fuel, use correct starting procedure, check spark plug, clean air filter.
Engine starts then dies	Clogged fuel filter, dirty carburetor, vent blocked	Replace fuel filter, clean carburetor, check tank vent.
Loss of power	Dirty air filter, clogged spark arrestor, old fuel	Clean/replace air filter, clean spark arrestor screen, use fresh fuel.
Excessive vibration	Bent shaft, unbalanced/damaged blade, loose parts	Inspect shaft and cutting attachment. Tighten all fasteners.
Cutting attachment does not spin	Broken drive cable, clutch worn, gearbox failure	Inspect drive shaft. Check clutch springs. See authorized STIHL dealer.

Service: For major repairs, contact an authorized STIHL servicing dealer. Use only STIHL original parts.