Stihl MM55 Manual

The Stihl MM55 is a multi-task power tool system featuring a modular design with interchangeable attachments, powered by a 2-stroke engine. It functions as a trimmer, edger, brushcutter, pole pruner, and blower. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Powerhead with 2-stroke engine, Drive shaft, Interchangeable attachments, Handle with controls, Fuel tank, Carrying harness.

Feature	Description
Powerhead	2-stroke engine with electronic ignition
Modular System	Quick-change attachment interface
Drive Shaft	Transfers power to attachments
Handle	Ergonomic design with throttle trigger and stop switch
Fuel Tank	Integrated tank for fuel/oil mixture
Carrying Harness	Reduces operator fatigue during extended use
STOP Switch	Immediately stops engine
Throttle Trigger	Variable speed control
Throttle Lockout	Prevents accidental throttle engagement
Choke Lever	Assists cold starting

Assembly & Installation

Unpack and inspect all components. Assemble on a clean, flat surface.

1. Attach handle: Align handle with mounting points on shaft, secure with provided bolts.
2. Install cutting attachment: For trimmer, attach cutting head or line spool as per instructions.
3. Connect drive shaft: Ensure shaft is properly engaged with powerhead coupler.
4. Fill fuel tank: Use fresh fuel/oil mixture (50:1 ratio with STIHL 2-stroke oil).

WARNING! Always wear protective gloves during assembly. Ensure all fasteners are tightened securely.

First-Time Operation

Before starting, put on safety gear: eye protection, hearing protection, gloves, long pants, and sturdy boots.

1. Check fuel level: Ensure adequate fuel/oil mixture.
2. Set choke: Move lever to cold start position for initial start.
3. Prime fuel system: Press primer bulb several times until fuel is visible.
4. Start engine: Place on ground, hold handle, pull starter cord briskly.
5. Warm up: Allow engine to run at idle for 30 seconds before applying load.

CAUTION! Never operate in enclosed spaces due to carbon monoxide risk. Keep bystanders at a safe distance.

Specifications

• Engine Type: 2-stroke, air-cooled.
• Displacement: 27.2 cc.
• Power Output: 0.9 kW (1.2 hp).
• Fuel/Oil Ratio: 50:1 (STIHL 2-stroke oil).
• Fuel Tank Capacity: 0.53 liters.
• Sound Power Level: 106 dB(A).
• Vibration Levels: Left/Right handle: 4.5/5.5 m/s².
• Weight (Powerhead): 5.3 kg.
• Attachment System: STIHL Quick-Change Interface.

Controls and Settings

Main controls located on handle. Powerhead features: STOP switch, Throttle trigger with lockout, Choke lever, Primer bulb.

Operation: Press throttle lockout while squeezing throttle trigger to increase engine speed. Release both to return to idle.

Adjustments: Handle position can be adjusted for operator comfort. Harness straps should be adjusted to distribute weight evenly.

Attaching Tools

Compatible attachments: Trimmer head, Brush knife, Edger, Pole pruner, Blower.

1. Stop engine and allow to cool.
2. Align attachment drive with powerhead coupler.
3. Push attachment onto powerhead until it clicks into place.
4. Tug gently to ensure secure connection.
5. For cutting tools, install appropriate guard before operation.

Tip: Always disconnect spark plug wire before changing attachments for safety.

Operating Procedures

Supports various yard maintenance tasks.

1. Trimming: Hold trimmer head parallel to ground, swing in arc motion.
2. Edging: Rotate shaft 90°, guide edger along pavement edge.
3. Brush cutting: Use sweeping motions from right to left.
4. Pole pruning: Secure footing, cut branches from stable position.
5. Blowing: Direct nozzle toward debris, use sweeping motions.

WARNING! Never operate above shoulder height. Watch for hidden obstacles like wires or rocks.

Safety Features

Throttle lockout: Prevents accidental acceleration. STOP switch: Immediate engine shutdown. Cutting attachment guard: Shields operator from debris. Anti-vibration system: Reduces operator fatigue.

Care & Maintenance

Allow engine to cool before maintenance. Clean air filter regularly. Check spark plug annually. Sharpen or replace cutting blades as needed.

CAUTION! Use only STIHL replacement parts. Never use automotive oil in fuel mixture.

Regulatory Information

EPA certified for emissions compliance. Meets ANSI safety standards for power tools. Copyright © STIHL Incorporated. All rights reserved. For support, visit www.stihlusa.com or contact 1-800-467-8445.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel issues, spark plug	Check fuel mixture; clean/replace spark plug; ensure choke is set correctly.
Engine runs poorly	Air filter, carburetor	Clean air filter; check fuel lines; adjust carburetor if needed.
Attachment doesn't turn	Drive connection	Ensure attachment is fully engaged; check drive shaft for damage.
Excessive vibration	Loose components, bent shaft	Tighten all fasteners; inspect shaft for damage.
Overheating	Airflow restriction	Clean cooling fins; check for debris around cylinder.

Storage: Empty fuel tank before long-term storage. Store in dry, protected area.

Service: 1-800-467-8445; www.stihlusa.com