STIHL KM 90 R Manual

The STIHL KM 90 R is a professional-grade KombiMotor powerhead, designed as the engine unit for STIHL's multi-tool system. It features a powerful 27.2 cc 2-stroke engine, electronic ignition (CDI), anti-vibration system, and a quick-release coupling for attaching various compatible attachments like brushcutters, hedge trimmers, pole pruners, and more. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: KM 90 R Powerhead, Quick-Release Coupling, Throttle Trigger with Lockout, Stop Switch, Choke/Start Assist Lever, Fuel Tank, and Anti-Vibration System.

Feature	Description
Engine	27.2 cc 2-stroke air-cooled engine with CDI ignition
KombiSystem	Quick-release coupling for multiple attachments
Anti-Vibration	Integrated system to reduce operator fatigue
Throttle Trigger Lockout	Prevents accidental throttle activation
Decompression Valve	Easier starting by reducing compression
Ergonomic Handle	Comfortable D-shaped handle with controls
Fuel Tank	Transparent for easy fuel level check
STIHL QuickStop	Inertia-activated chain brake (when used with cutting attachments)
Muffler	Spark-arresting muffler for reduced emissions and noise
Warranty	STIHL professional warranty (terms apply)

Safety Instructions

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

1. Personal Protective Equipment (PPE): Always wear safety glasses, hearing protection, gloves, sturdy boots, and long pants.
2. Work Area Safety: Keep bystanders, children, and pets at least 50 feet away. Be aware of your surroundings.
3. Fuel Safety: Refuel outdoors only, with engine stopped and cool. Use clean, approved gasoline/oil mix. Wipe up spills.
4. Operation: Hold unit firmly with both hands. Do not operate in poor lighting, bad weather, or when fatigued.
5. Kickback Awareness: Understand kickback forces, especially when using cutting attachments. Use reduced-kickback guide bars and chains.

WARNING! Improper use can cause serious or fatal injury. Never modify the unit. Use only STIHL-approved attachments and accessories.

Assembly & First Use

Assemble your KombiSystem with the desired attachment.

1. Attach Handle/Shaft: Align the attachment drive shaft with the powerhead coupling. Push together until they click. Pull back on the coupling sleeve to lock.
2. Add Attachment: Attach the tool head (e.g., brushcutter, hedge trimmer) to the other end of the shaft per its manual.
3. Fuel Mix: Use high-quality 89+ octane gasoline mixed with STIHL HP Ultra 2-stroke oil at a 50:1 ratio. Shake container well before filling.
4. Starting: Place unit on clear, flat ground. Set master control lever to choke (cold start) or run (warm start). Press fuel primer bulb 5 times. Pull starter cord briskly.
5. Break-in Period: Operate at varied speeds (no full throttle) for the first 3 tank fillings to allow engine components to seat properly.

CAUTION! Ensure all couplings are securely locked before starting the engine.

Specifications

• Powerhead Model: KM 90 R
• Engine Displacement: 27.2 cc
• Engine Power: 1.3 kW / 1.8 hp
• Fuel/Oil Ratio: 50:1 (STIHL HP Ultra oil)
• Fuel Tank Volume: 0.53 liters (18 fl. oz.)
• Idle Speed: 2,800 rpm (factory set)
• Maximum Powerhead Speed: 12,500 rpm
• Weight (Powerhead only): 5.4 kg (11.9 lbs)
• Sound Pressure Level: Approx. 99 dB(A)
• Vibration Level (left/right): Approx. 4.5/4.5 m/s²
• Warranty: Refer to your STIHL warranty statement.

Controls and Operation

Master Control Lever: Choke/Start/Stop/Run positions. Throttle Trigger: Controls engine speed. Throttle Trigger Lockout: Must be depressed to allow throttle activation. Stop Switch: "0" stops engine, "I" run position. Quick-Release Coupling: For attaching drive shafts.

Starting Procedure (Cold Engine):

1. Press fuel primer bulb at least 5 times.
2. Set master control lever to choke position (full left).
3. Pull starter handle briskly until engine fires (usually 2-5 pulls).
4. Immediately move master control lever to run position (middle).
5. Pull starter again to start. Allow 10-15 seconds to warm up at idle.

Stopping: Release throttle, let engine idle briefly, move master control lever to STOP (0).

Attaching Tools

The KM 90 R is compatible with STIHL KombiSystem attachments.

1. Ensure engine is OFF and cool.
2. Pull back the quick-release coupling sleeve on the powerhead.
3. Insert the drive shaft coupling pin into the powerhead socket.
4. Release the sleeve to lock. Tug firmly to confirm secure connection.
5. Attach the tool head (e.g., PolyCut head, circular saw, hedge trimmer) to the opposite end of the shaft according to its specific manual.
6. Always use the correct harness and handle configuration for the tool being used.

Tip: Keep coupling surfaces clean and lightly lubricated with STIHL coupling grease for easy connection and disconnection.

Fuel & Lubrication

Use only fresh, unleaded gasoline with a minimum octane rating of 89. Mix with STIHL HP Ultra 2-stroke oil at a 50:1 ratio.

1. Mixing: Add oil to an approved fuel can first, then add gasoline. Close can and shake vigorously for 10 seconds.
2. Refueling: Stop engine and allow to cool. Clean area around fuel cap. Open cap slowly. Use a funnel. Do not overfill. Tighten cap securely.
3. Gearbox Lubrication: Attachment gearboxes (e.g., brushcutter head, hedge trimmer) require regular greasing with STIHL special grease. Consult attachment manual.
4. Air Filter: Check before each use. Clean with compressed air or wash in soapy water (if foam). Allow to dry completely before re-oiling (if applicable) and reinstalling.

WARNING! Never use fuel older than 60 days. Old fuel can cause starting and performance issues and damage the engine.

Maintenance Schedule

Regular maintenance ensures long life and safe operation.

Component	Before Each Use	Every 25 Hours	Every 50 Hours	Every 100 Hours
Air Filter	Check/clean	-	Replace*	-
Spark Plug	Check	-	Clean/gap	Replace
Fuel Filter	-	-	Replace	-
Spark Arrestor Screen	-	-	Check/clean	-
Anti-Vibration Elements	Check	-	-	Inspect/Replace
External Screws/Nuts	Check tightness	Tighten	-	-
Carburetor Adjustment	-	-	Check**	-

*Replace more often in dusty conditions.
**Should only be performed by a STIHL-trained technician.

Storage

Prepare unit for storage if it will not be used for more than 30 days.

1. Fuel System: Run engine until it stops from fuel starvation to empty the carburetor. Alternatively, add fuel stabilizer to a full tank and run for 5 minutes.
2. Cleaning: Thoroughly clean the entire unit, removing dirt, debris, and plant sap.
3. Storage Location: Store in a dry, well-ventilated, and secure place, out of reach of children.
4. Battery (if electronic ignition accessory): Remove and store separately in a cool, dry place.
5. Attachments: Store separately. Lightly oil metal cutting surfaces to prevent rust.

CAUTION! Never store the unit with fuel in the tank in an enclosed, poorly ventilated area due to fire and fume hazards.

Warranty & Compliance

This STIHL product is covered by a limited warranty. See your STIHL warranty statement for full terms, conditions, and duration. This engine meets U.S. EPA and CARB emission regulations for handheld engines. The spark arresting muffler meets USDA Forest Service requirements. For genuine parts, accessories, and service, see your authorized STIHL servicing dealer. For support, visit www.stihlusa.com or contact STIHL Incorporated at 1-800-467-8445.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	1. No fuel. 2. Flooded engine. 3. Choke not set correctly. 4. Spark plug faulty.	1. Check fuel level, primer bulb. 2. Move control to run, hold throttle open, pull starter many times. 3. Set choke for cold/warm start. 4. Check, clean, gap, or replace plug.
Engine starts but dies	1. Dirty air filter. 2. Old/bad fuel. 3. Clogged fuel filter.	1. Clean or replace air filter. 2. Drain tank, use fresh 50:1 mix. 3. Replace in-tank fuel filter.
Loss of power	1. Clogged spark arrestor. 2. Dirty air filter. 3. Carburetor needs adjustment.	1. Clean muffler spark arrestor screen. 2. Clean air filter. 3. See authorized STIHL dealer.
Excessive vibration	1. Loose attachment. 2. Damaged drive shaft. 3. Worn anti-vibration mounts.	1. Check and secure all couplings. 2. Inspect shaft for bends/damage. 3. Have dealer inspect/replace mounts.
Attachment does not turn	1. Coupling not engaged. 2. Drive shaft disconnected. 3. Gearbox damaged.	1. Re-engage quick-release coupling. 2. Check shaft connections at both ends. 3. Consult dealer for specific attachment.

Dealer Service: For repairs beyond basic maintenance, take your STIHL KM 90 R to an authorized STIHL servicing dealer.

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