Stihl MS 192 T Service Manual

The Stihl MS 192 T is a lightweight, professional-grade top-handle chainsaw designed for arborists and tree care professionals. This service manual provides detailed instructions for maintenance, troubleshooting, and repair procedures to ensure optimal performance and safety. Below are key sections covering specifications, safety, maintenance schedules, component identification, disassembly/assembly, fuel system, ignition system, carburetion, and troubleshooting.

Specifications & Identification

Key identification data: Model MS 192 T, serial number location on crankcase.

Specification	Description
Engine Displacement	30.1 cm³ (1.84 cu. in.)
Power Output	1.3 kW (1.8 bhp)
Fuel Tank Volume	0.25 L (0.07 US gal)
Oil Tank Volume	0.20 L (0.05 US gal)
Weight (Powerhead)	3.2 kg (7.1 lbs)
Guide Bar Lengths	30-35 cm (12"-14")
Chain Pitch	1/4" PMM3 or .325" PMM
Ignition System	Electronic, capacitor discharge
Carburetor	Zama C1Q-S series
Spark Plug	Bosch WSR 6 F or equivalent

Safety Precautions

Always prioritize safety before performing any service. Disconnect spark plug boot.

1. Work in a clean, well-ventilated area.
2. Use proper Stihl special tools where specified.
3. Replace all gaskets, seals, and snap rings during reassembly.
4. Torque fasteners to specifications using a calibrated torque wrench.
5. Use only genuine Stihl replacement parts.

WARNING! Fuel is highly flammable. No smoking. Allow engine to cool completely before servicing. Wear cut-resistant gloves when handling the chain.

Maintenance Schedule

Follow this schedule to maintain performance and longevity.

1. Before each use: Check chain tension, sharpness, and lubrication. Inspect for loose fasteners.
2. Daily: Clean air filter, check fuel filter, clean cooling fins and guide bar groove.
3. Weekly: Inspect spark plug, fuel lines, and impulse line. Clean spark arrestor screen (if equipped).
4. Monthly: Check clutch, sprocket, and anti-vibration elements. Clean carburetor compartment.
5. Annually: Check cylinder/piston condition, crankshaft seals, and all bearings. Replace fuel filter.

CAUTION! Failure to follow maintenance intervals may void warranty and lead to premature failure.

Component Overview

• Engine: Single cylinder, two-stroke, piston ported.
• Fuel System: Diaphragm carburetor with manual fuel pump, integrated fuel filter.
• Ignition: Solid-state electronic module with stop switch.
• Clutch: Centrifugal, drum-type with integrated rim sprocket.
• Chain Brake: Inertia-activated with manual release.
• Anti-Vibration: Spring-dampened front and rear handles.
• Decompression Valve: Standard for easier starting.
• Oiling System: Automatic, adjustable chain oil pump.

Disassembly Procedures

General sequence for major disassembly.

Top Handle/Cover Removal: Remove starter cover screws, lift off cover. Disconnect choke linkage. Remove handle mounting nuts.

Cylinder Removal: Remove muffler. Remove cylinder base nuts. Gently tap cylinder with plastic mallet to break gasket seal. Lift cylinder off crankcase.

Crankcase Splitting: Remove all external components (carburetor, ignition, clutch). Remove crankcase screws in crisscross pattern. Separate crankcase halves using a splitting tool. Do not pry.

Clutch/Sprocket Removal: Hold piston at Top Dead Center (TDC). Use clutch holding tool and socket to remove clutch nut (left-hand thread). Remove clutch drum and rim sprocket.

Assembly Procedures

Reverse of disassembly with critical notes.

1. Clean all parts in solvent and air dry. Inspect for wear.
2. Lubricate bearings and seals with two-stroke oil during assembly.
3. Use new gaskets and seals. Apply a thin film of sealant to crankcase mating surfaces if specified.
4. Torque cylinder nuts to 20 Nm (15 ft-lb) in crisscross pattern.
5. Torque crankcase screws to 10 Nm (7.5 ft-lb) in proper sequence.
6. Set ignition air gap to 0.3 mm (0.012 in).
7. Adjust clutch spring tension upon reassembly.

Tip: Refer to exploded-view diagrams for correct orientation of parts.

Fuel System Service

Servicing the carburetor, fuel lines, and tank.

1. Carburetor Removal: Disconnect fuel line and impulse line. Remove mounting nuts. Lift carburetor off.
2. Diaphragm & Gasket Kit: Replace all diaphragms, gaskets, and needle valve during overhaul.
3. Fuel Filter: Replace annually or if clogged. Access through fuel tank filler neck.
4. Fuel Lines: Inspect for cracks or hardening. Replace if deteriorated.
5. Impulse Line: Check for leaks; a faulty line causes poor fuel delivery.

WARNING! Use only ethanol-resistant fuel lines. Clean carburetor jets with compressed air, not wire.

Ignition System Service

Testing and replacing ignition components.

Spark Test: Remove spark plug, reconnect boot. Hold plug base against cylinder. Pull starter; look for strong blue spark. No spark indicates faulty module, boot, or stop switch.

Module Resistance Test: Disconnect module. Primary coil resistance: ~0.5-2.0 Ω. Secondary (spark plug lead): ~5-15 kΩ. Refer to exact values in wiring diagram.

Flywheel Removal: Use flywheel puller. Do not strike with hammer.

Air Gap: Set between flywheel magnets and ignition module legs to 0.3 mm.

Carburetor Adjustment

Standard settings and fine-tuning. Engine must be at operating temperature.

Screw	Initial Setting	Function
L (Low Speed)	1 turn open	Idle and low-speed mixture
H (High Speed)	1 turn open	High-speed/WOT mixture
LA (Idle Speed)	1.5 turns open	Governs idle RPM

1. Start saw and warm up for 3-5 minutes.
2. Turn L screw for smoothest acceleration from idle.
3. At WOT (no load), adjust H screw for peak RPM (do not exceed max RPM spec).
4. Adjust LA screw so chain just stops moving at idle.
5. Re-check acceleration. Final settings may vary with altitude/temperature.

Chain & Bar Maintenance

Proper care extends life and ensures safe operation.

• Sharpening: Use correct round file size. Maintain correct filing angle (30°) and depth gauge clearance.
• Tension: Correct when chain snaps back after pulling away from bar. Adjust when cold.
• Bar: Regularly clean oil grooves and flip bar to ensure even wear. Dress bar rails with a flat file if burred.
• Sprocket: Inspect for wear. Replace rim sprocket or drum if teeth are hooked.
• Oiling: Check oil output. Adjust oil pump screw if necessary. Use only recommended bar and chain oil.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, flooded, fuel issue	Check spark, plug condition. Dry plug. Check fuel lines, filter, carburetor diaphragms.
Engine starts then dies	Fuel starvation, air leak	Check fuel vent, filter, carburetor. Perform pressure/vacuum test on crankcase.
Lacks power at high speed	Clogged air filter, exhaust screen, H screw	Clean/replace filter. Clean spark arrestor. Adjust H screw.
Excessive vibration	Unbalanced chain, loose parts, AV mounts	Sharpen/balance chain. Tighten fasteners. Inspect anti-vibration buffers.
Chain does not oil	Clogged oil passages, faulty pump, wrong oil	Clean bar groove and oil ports. Check pump drive and diaphragm. Use correct oil viscosity.
Chain rotates at idle	Idle speed too high, clutch springs	Adjust LA screw. Inspect clutch springs for wear/breakage.

Special Tools: Flywheel puller (1140 890 4500), clutch holding tool (0000 893 4303), crankcase splitting tool.

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