STIHL KM110R Repair Manual

The STIHL KM110R is a professional-grade KombiMotor powerhead designed for use with various STIHL attachments (e.g., trimmer, brushcutter, pole pruner, edger). This manual provides comprehensive repair, maintenance, and troubleshooting information for the KM110R engine and drive system. Below are key sections covering safety, specifications, disassembly, component repair, assembly, and troubleshooting procedures.

1. Safety Precautions 2. Specifications & Technical Data 3. Tools & Equipment Required 4. Engine Disassembly Procedure 5. Carburetor Service & Adjustment 6. Ignition System Diagnosis 7. Fuel System Repair 8. Drive Shaft & Gearbox Service 9. Reassembly & Torque Specifications 10. Maintenance Schedule 11. Troubleshooting Guide

Safety Precautions

Before performing any repair, ensure the engine is off, cool, and the spark plug boot is disconnected. Wear appropriate personal protective equipment (PPE).

Hazard	Precaution
Fuel Fire/Explosion	Drain fuel tank before service. Work in well-ventilated area away from ignition sources.
Sharp Edges	Wear cut-resistant gloves when handling cutting attachments or internal components.
Hot Surfaces	Allow engine and muffler to cool completely before disassembly.
Spring Tension	Use caution when removing recoil starter; spring is under tension.
Chemical Exposure	Use gloves when handling fuel, oil, or cleaning solvents.

Specifications & Technical Data

Engine Type: STIHL 2-MIX engine, single-cylinder, air-cooled.
Displacement: 31.8 cc (1.94 cu. in.).
Power Output: 1.3 kW (1.8 hp).
Fuel/Oil Mix: 50:1 (STIHL HP Ultra or equivalent ISO-L-EGD certified oil).
Idle Speed: 2,800 rpm.
Max. Engine Speed: 13,000 rpm (with cutting attachment).
Ignition System: Electronic, capacitor discharge (CDI).
Carburetor: Zama C1Q-S series, adjustable.
Drive System: Flexible drive shaft with modular gearbox.
Weight (Powerhead): Approximately 5.9 kg (13 lbs).

Tools & Equipment Required

Standard and STIHL-specific tools needed for repair.

STIHL special wrench for spark plug.
Torx screwdrivers (T10, T15, T25).
Socket set (8mm, 10mm, 13mm).
Carburetor adjustment tool (splined).
Compression tester (expected: 120-150 psi).
Feeler gauges for spark plug gap (0.5 mm / 0.020 in).
Multimeter for ignition testing.
Flywheel puller (STIHL part # 5910 890 4500).
Clutch removal tool.

WARNING! Use STIHL-approved tools to avoid damage to components.

Engine Disassembly Procedure

Step-by-step teardown of KM110R powerhead.

Remove cutting attachment and drive shaft extension.
Drain fuel and oil from gearbox (if equipped).
Remove air filter cover, filter, and carburetor box.
Disconnect fuel lines and throttle linkage.
Remove muffler and cylinder cover.
Remove recoil starter assembly.
Remove flywheel (use puller).
Remove clutch assembly (use clutch tool).
Separate crankcase halves after removing all screws.

CAUTION! Label all parts and fasteners. Note orientation of gaskets and seals.

Carburetor Service & Adjustment

Servicing the Zama C1Q-S carburetor.

Adjustment	Procedure	Default Setting
Idle Speed (L)	Turn screw until engine idles smoothly without stalling.	1 turn out from lightly seated
High Speed (H)	Adjust for max RPM without leaning (use tachometer).	1 turn out from lightly seated
Idle Limiter (LA)	Sets minimum idle speed; factory preset.	Do not adjust unless necessary

Cleaning: Disassemble carburetor, soak in cleaner, blow out passages with compressed air. Replace diaphragm and gaskets if hardened or damaged.

Ignition System Diagnosis

Testing the CDI module, spark plug, and stop switch.

Check spark plug: Replace if electrode worn; gap to 0.5 mm.
Test for spark: Remove plug, ground to cylinder, pull starter. Look for strong blue spark.
If no spark: Check stop switch wire for continuity to ground (should be open when switch is ON).
Test ignition coil resistance: Primary: 0.5-2.0 Ω; Secondary: 8-15 kΩ.
Replace CDI module if tests fail and spark plug/wiring are good.

Tip: A weak or intermittent spark often indicates a failing ignition coil.

Fuel System Repair

Fuel line, filter, and tank service.

Replace fuel filter inside tank annually or if clogged.
Inspect fuel lines for cracks, stiffness, or leaks. Replace if deteriorated.
Clean fuel tank vent. Test by opening cap; if suction is present, vent is blocked.
Check fuel pickup line inside tank for cracks.
Ensure primer bulb (if equipped) is soft and pliable; replace if hardened.

WARNING! Use only ethanol-free fuel or fuel with ≤10% ethanol to prevent carburetor damage.

Drive Shaft & Gearbox Service

Servicing the flexible drive shaft and attachment gearbox.

Drive Shaft: Remove and inspect for kinks or wear. Lubricate with STIHL drive shaft grease.
Gearbox: Drain old grease. Inspect gears for pitting or wear. Repack with STIHL gear grease.
Bearings: Check for smooth rotation; replace if rough or noisy.
Output Shaft Seal: Replace if leaking grease.

Reassembly: Ensure drive shaft is fully engaged in crankcase and gearbox before tightening fasteners.

Reassembly & Torque Specifications

Critical torque values for engine and drive components.

Component	Torque	Notes
Cylinder bolts	10 Nm (88 in-lb)	Crisscross pattern
Crankcase screws	8 Nm (71 in-lb)	Evenly tighten
Clutch nut	40 Nm (30 ft-lb)	Right-hand thread
Flywheel nut	35 Nm (26 ft-lb)	Use locking compound
Spark plug	20 Nm (15 ft-lb)	Do not overtighten

Always replace gaskets, seals, and lock washers. Apply appropriate sealant to crankcase mating surfaces.

Maintenance Schedule

Recommended service intervals for KM110R.

Daily: Check for loose fasteners, leaks, damage. Clean air filter if dirty.
25 Hours: Clean spark arrestor screen (if equipped). Check fuel filter.
50 Hours: Replace air filter. Clean cooling fins. Inspect drive shaft.
100 Hours: Replace spark plug. Clean carburetor and fuel tank. Service gearbox.
Annual: Replace fuel lines. Full engine tune-up and compression test.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, fuel, or compression	Check spark plug, fuel delivery, and compression (min. 90 psi).
Engine starts then dies	Clogged fuel filter, bad vent, carburetor issue	Replace fuel filter, clean tank vent, service carburetor.
Loss of power	Dirty air filter, clogged spark arrestor, exhaust port carbon	Clean/replace air filter, clean spark arrestor, decarbonize exhaust.
Excessive vibration	Unbalanced cutting attachment, bent drive shaft, loose engine mounts	Balance attachment, inspect drive shaft, tighten mounts.
Gearbox overheating	Low grease, damaged gears, misalignment	Repack with grease, inspect gears, ensure proper alignment.
Attachment won't spin	Sheared drive pin, stripped gearbox, clutch slipping	Replace drive pin, inspect gearbox, adjust/replace clutch.

Service Support: For genuine STIHL parts and technical assistance, contact an authorized STIHL dealer or visit www.stihlusa.com.