Stihl FS 120 Service Manual
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Stihl FS 120 Service Manual

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  • Page 2: Table Of Contents

    (FS 120...350, FR 350) 26 Repair 5.3.3 Removing and Installing (FS 120/200) (FS 400/450, FR 450) 27 Repair Flywheel (FS 300...450) Short Circuit Wire Repair (FR 350/450) © 1997, Andreas Stihl, Waiblingen FS 120, 200, 300, 350, 400, 450, FR 350, 450...

  • Page 3: Introduction

    Servicing and repairs are made considerably easier if the machine is mounted on assembly stand (2) 5910 890 3100 with the aid of clamp (1) 5910 890 8800. FS 120, 200, 300, 350, 400, 450, FR 350, 450...

  • Page 4: Specifications

    Fuel mixture: Regular brand name gasoline and two-stroke engine oil Mix ratio: 50:1 with STIHL two-stroke engine oil 25:1 with other brand name two-stroke, air-cooled engine oils Air filter: Paper filter FS 120, 200, 300, 350, 400, 450, FR 350, 450...

  • Page 5: Ignition System

    FS 120, 200, 300, 350, FR 350 4134 007 1050 Set of gaskets for FS 400, 450, FR 450 4128 007 1050 FS 400/450 only ** FS 120, 200, 350 and 450 FS 120, 200, 300, 350, 400, 450, FR 350, 450...

  • Page 6: Tightening Torques

    Spline screw IS-M5x16 AV sleeve/drive tube (clamp screw) Spline screw IS-M5x12 Clamp/control handle/drive tube 2) 5) Spline screw IS-M5x16 Clamp/drive tube (for harness) Spline screw IS-M5x30 Control handle (bike handle) FS 120, 200, 300, 350, 400, 450, FR 350, 450...
  • Page 7 2) FR 450 3) FS 120/200 4) FS 300/350 5) FR 350 6) with washer Note: Power screwdriver speed settings for polymer: Plastoform screws max. 600 rpm DG screws max. 500 rpm FS 120, 200, 300, 350, 400, 450, FR 350, 450...

  • Page 8: Clutch

    Troubleshooting chart - see "Standard Repairs, Trouble- shooting" handbook.  Remove clutch housing - see 9.1 or 11.2. • FS 120...350, FR 350 Remove clutch shoes with • Fit locking strip (1) bushings. 0000 893 5903. FS 400/450, FR 450 •...

  • Page 9: Clutch Carrier

    Clutch Carrier  Pull locking strip out of cylinder.  Fit spark plug and tighten down to 20 Nm (15 lbf.ft). Important: If the spark plug comes with a separate terminal nut, always fit the nut on the thread and tighten it down securely.

  • Page 10: Engine

     Lift away the muffler. Muffler Spark arresting screen FS 400/450, FR 450  Remove air filter cover - see 8.1. FS 120...350, FR 350 • Pull spark arresting screen out of the muffler.  Clean or replace spark arresting screen if necessary.

  • Page 11: Leakage Test

    Leakage Test 4.2.1 Preparations Defective oil seals, gaskets,  Remove the carburetor - see cracks in castings or a faulty seal- 8.2.1 and 8.2.2. ing ring between the carburetor housing and cylinder are the  Set the piston to top dead center usual causes of leaks.

  • Page 12: Pressure Test

    4.2.2 Pressure Test 4.2.3 Vacuum Test Oil seals tend to fail when sub- jected to a vacuum, i.e. the sealing lip lifts away from the crankshaft during the piston’s induction stroke because there is no internal counterpressure. An additional test can be carried out with the vacuum pump to detect this kind of fault.

  • Page 13: Oil Seals

    Oil Seals Note: If the vacuum reading It is not necessary to disassemble remains constant, or rises to no the complete engine to replace the more than 0.3 bar (4.25 psi) within oil seals. 20 seconds, it can be assumed that the oil seals are in good The FS 200 engine is shown in the condition.

  • Page 14: Exposing The Cylinder

    Exposing the Cylinder Always check and, if necessary, repair the fuel system, carburetor, air filter and ignition system before looking for faults on the engine. Troubleshooting chart - see "Standard Repairs, Trouble- shooting" handbook.  Remove the muffler - see 4.1.  Remove the carburetor - see •...

  • Page 15: Cylinder And Piston

     Preparations - see 4.4.  Remove clutch housing - see 9.1 and 11.2.  Pull off the spark plug boot.  On FS 120...350, FR 350: Take ignition lead out of the retainers on the throttle cable holder.  Unscrew the spark plug.

  • Page 16: Installation

    4.5.2 Installation • • • Now use the assembly drift (2) Thoroughly clean the gasket Push the assembly drift, small 1110 893 4700 to push the pis- seating surface (1). diameter first, through the piston ton pin (1) out of the piston. and small end (needle cage) and •...
  • Page 17 • • Use installing tool (1) Lubricate piston and piston rings  Lubricate the inside of the 5910 890 2208 to fit the snap with oil. Rest piston (1) on cylinder with oil and line it up so rings. wooden assembly block (2) that it is positioned as it will be in 1108 893 4800.

  • Page 18: Piston Rings

    • Remove top of cable guide (2). FS 120...350, FR 350 • • All models Install the new piston rings in the Take throttle cable (1) out of •...
  • Page 19 • Hold ZS installing tool against clutch side of crankcase so that the notch marked "16" is at the bottom. • Insert M6x20 screws (2) in holes marked "17" and tighten them down against the drilled plate.  Remove the flywheel - see 5.4.  Remove the piston - see 4.5.1.
  • Page 20 (2). bottom. • Turn thrust bolt (3) clockwise until the crankshaft is released from the ball bearing. FS 120...350, FR 350  Back off spindle (left-hand thread) of ZS installing tool 5910 890 2220 a little. • • Insert screws (1) 9022 341 1190...

  • Page 21: Installing Crankshaft

    4.7.2 Installing Crankshaft Each half of the crankcase may Note: This operation must be be replaced separately. carried out very quickly because the bearing absorbs heat immedi- New crankcases come with ately and begins to expand. factory-installed ball bearings. If the original crankcase is used again, remove the gasket residue and clean the mating surfaces - they must be cleaned very...
  • Page 22 • • • Fit ball bearing in crankcase by Position the straight stub of the Hold the spindle steady and hand and push it home as far as crankshaft in the bearing at the rotate sleeve counterclockwise stop. clutch side of the crankcase. until it butts against the ball bearing.
  • Page 23 • •  Slide the oil seal, open side Fit starter side of crankcase over Hold the sleeve steady and the crankshaft stub. rotate spindle clockwise until the facing the crankcase, over the two halves of the crankcase are installing sleeve. together.

  • Page 24: Decompression Valve

    Decompression Valve IGNITION SYSTEM Spark Plug Boot Warning! Exercise extreme  Remove the shroud - see 4.1. caution when carrying out maintenance and repair work on  Pull off the spark plug boot. the ignition system. The high voltages which occur can cause  On FS 400/450, FR 450, take serious or even fatal accidents! cable holder off the cylinder.

  • Page 25: Ignition Lead (Fs 400/450, Fr 450)

    Ignition Lead (FS 400/450, FR 450)  On FS 400/450, FR 450, attach the cable retainer to the cylinder.  Fit the boot on the spark plug.  Fit the shroud - see 4.1. • Pinch hook of leg spring into the  Remove the ignition module - center of the lead, i.e.

  • Page 26: Ignition Module

    The ignition module accommo- dates all the components required to control ignition timing. FS 120...350, FR 350 There are two electrical connec- tions on the coil body: 1. the high voltage output (1) with ignition lead (2) 2.

  • Page 27: Ignition Timing

    5.3.1 Ignition Timing 5.3.2 Removing and Installing (FS 120...350, FR 350) Ignition timing is not adjustable.  Remove the shroud - see 4.1. Since there is no mechanical wear  Pull the boot off the spark plug. in these systems, ignition timing cannot get out of adjustment.

  • Page 28: Removing And Installing (Fs 400/450, Fr 450)

    5.3.3 Removing and Installing (FS 400/450, FR 450) •  Place the module in position,  Remove the shroud - see 4.1. Take out the screws. insert the screws but do not  Remove the fan housing - see tighten them down yet. 6.2.

  • Page 29: Flywheel

    Unscrew the flywheel nut.  Fit flywheel nut. Tighten nut on  Pull off the flywheel. FS 120 to 24 Nm (17.7 lbf.ft). Tighten nut on all other models to 32 Nm (23.6 lbf.ft). )6       )5  ...

  • Page 30: Short Circuit Wire

    Take out the screw (1). •  Remove the muffler - see 4.1. Remove top of cable guide (2). • Push out the outer grommet (1). FS 120...350, FR 350 • Pull short circuit wire out of housing bore and remove grommet. •...

  • Page 31: Rewind Starter

     It should be lubricated with a few the starter mechanism is in order but plugged with dirt. At very low drops of STIHL special lubricant outside temperatures the lubri- before installation - see 13.2. cating oil on the rewind spring may thicken and cause the spring windings to stick together.

  • Page 32: Tensioning

    6.2.2 Tensioning  Hold the starter grip firmly to keep the rope tensioned.  Let go of the rope rotor and slowly release the starter rope so that it can rewind properly. • • Engage outer spring loop in the Make a loop in the starter rope.

  • Page 33: Starter Rope/Starter

    Starter Rope/Starter Grip (ElastoStart)  Remove fan housing with rewind starter - see 6.2. Starter rope  Remove rope rotor - see "Standard Repairs, Trouble- shooting" handbook.  Remove the starter rope from the rotor. • • Pull the rope back to locate the Thread rope through the hole in knot in the starter grip.

  • Page 34: Throttle Control

    THROTTLE CONTROL Throttle Trigger/Interlock Lever (Bike Handle) • • • Remove the torsion spring. Take out screw and washer. Attach the throttle cable, then position torsion spring as shown  Pull off the control handle. and push its long arm into the slot.

  • Page 35: Throttle Trigger/Interlock Lever (Loop Handle)

    Contact Springs/Detent Spring in Control Handle Throttle Trigger/Interlock (Bike Handle) Lever (Loop Handle) •  Remove the throttle trigger - see Take out slide control’s collar FR 350/450 • Use screwdriver (1) 5910 890 screw (1). 7.1. 2301 to remove screw. •...

  • Page 36: Slide Control

    Slide Control (Loop Handle) • • Pull throttle trigger (1) with Pull interlock lever with contact  Remove the interlock lever - see throttle cable (2) off the peg. spring off the peg. 7.3. • Pull slide control off the handle molding.

  • Page 37: Throttle Cable

    9.1 and 11.2.  Remove the air filter - see 8.1.  Take throttle cable off the con- tact spring - see 7.2 and 7.3. Note: On FS 120...350, FR 350, • Assemble in the reverse sequence. Disconnect throttle cable nipple...

  • Page 38: Adjusting

    Make sure grommet is properly located in the carburetor housing.  Secure lug between the raised marks. FS 120...350, FR 350  Place lug and extended throttle cable in the corner of the filter housing.  Tighten screw of extended throttle cable to 6.0 Nm...

  • Page 39: Air Filter

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  • Page 40: Carburetor

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  • Page 41  5HPRYLQJ DQG ,QVWDOOLQJ • • 5HPRYH WKH JDVNHW 3U\ FKRNH NQRE RXW RI FDUEXUHWRU FS 400/450, FR 450 KRXVLQJ DQG SXOO LW RII WKH FKRNH 5HDVVHPEOH LQ WKH UHYHUVH VKDIW  5HPRYH WKH VKURXG  VHH  VHTXHQFH • 7DNH RXW VFUHZ    8VH D QHZ JDVNHW •...

  • Page 42: Leakage Test

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  • Page 45: Tank Vent

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  • Page 46  7LJKWHQ GRZQ VFUHZV WR  1P   OEIIW  )6  )5  FS 120...350, FR 350  2Q )5  UHPRYH SRZHUKHDG  2Q )5  UHPRYH SRZHUKHDG IURP VXSSRUW IUDPH  VHH  IURP VXSSRUW IUDPH  VHH  •...
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  • Page 48: Av System

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  • Page 50 •  6OLS WKH UXEEHU EXIIHUV RYHU WKH 3XVK VXSSRUW LQ GLUHFWLRQ RI $9 SHJV RQ WKH FOXWFK KRXVLQJ DQG KRXVLQJ XQWLO WKH IRXU VWHHO EDUV VXSSRUW DUH WLJKW  &RDW UXEEHU EXIIHUV ZLWK D OLWWOH  7LJKWHQ GRZQ VFUHZ WR  1P OXEULFDQW HJ ZDVKLQJXS OLTXLG   OEIIW   3XVK $9 KRXVLQJ RQWR WKH UXE...
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  • Page 52: Shaft

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  • Page 53: Loop Handle

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  • Page 54: Flexible Liner

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  • Page 55: Drive Tube

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  • Page 57: Gearhead

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  • Page 58: Clutch Drum

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  • Page 59: Repair

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  • Page 60: Special Servicing Tools

    - Sleeve (4x) 1123 851 8300 1) 2) - Extension 4116 894 1000 1) 2) - Spline screw 9022 341 1190 1) 2) Puller 4119 890 4600 Removing crankshaft (clutch side) FS 120, 200, 300, 350, 400, 450, FR 350, 450...
  • Page 61 4) Equivalent to puller 0000 890 4400, but with longer spindle 5910 890 8400. 5) Always use torque wrench to tighten DG/P screws. 6) Wrench has optical/acoustic signal. 7) On DG/P screws, use for releasing only. FS 120, 200, 300, 350, 400, 450, FR 350, 450...

  • Page 62: Servicing Aids

    - 225 g/8 oz tube: 0781 120 1110 STIHL gear lubricant Gearhead lubrication - 80 g/3 oz tube: 0781 120 1117 - 225 g/8 oz tube: 0781 120 1119 FS 120, 200, 300, 350, 400, 450, FR 350, 450...

This manual is also suitable for:

Fs 200Fr 350Fr 450 fs 450 fs 400Fs 300 ... Show all

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