Stihl 4144 series User manual

STIH)

STIHL Series 4144 Components

FC, FS, KM 2008-02

FS 40, FS 50, FS 56

FC 56

KM 56

1Series 4144 Components FC, FS, KM

RA_545_01_01_01

1. Introduction 2

2. Safety Precautions 3

3. Specifications 4

3.1 Engine 4

3.2 Fuel System 4

3.3 Ignition System 4

3.4 Tightening Torquese 5

4. Troubleshooting 7

4.1 Clutch 7

4.2 Rewind Starter 8

4.3 Ignition System 9

4.4 Carburetor 11

4.5 Engine 14

5. Engine 15

5.1 Removing and

Installing 15

5.2 Leakage test 16

5.3 Oil seals 16

5.4 Ignition Module /

Spark Plug Boot 16

5.5 Clutch 16

5.6 Flywheel 16

5.7 Motor 16

5.8 Muffler / Spark

Arresting Screen 19

5.9 Short Circuit Wire 20

5.9.1 Testing 20

5.9.2 Removing and

Installing

(Loop Handle Version) 20

5.9.3 Removing and

Installing

(Bike Handle Version) 23

5.9.4 Ground Wire 26

5.10 Ignition System

Troubleshooting 27

6. Rewind Starter 30

6.1 General 30

6.2 Removing and

Installing 30

6.3 Pawls 30

6.3.1 Carrier 31

6.4 Rope Rotor 32

6.5 Starter Rope / Grip 33

6.6 Tensioning the

Rewind Spring 35

6.7 Replacing the

Rewind Spring 36

6.8 ErgoStart 36

7. Control Levers 37

7.1 Switch Shaft /

Control Lever 37

7.2 Switch Positions 37

7.3 Interlock Lever

(Loop Handle) 37

7.3.1 Throttle Trigger 38

7.4 Throttle Trigger/

Interlock Lever

(Bike Handle) 40

7.5 Handlebar

(Bike Handle) 43

8. Fuel System 44

8.1 Air Filter 44

8.1.1 Baffle 44

8.1.2 Filter housing 44

8.2 Removing and

Installing

the Carburetor 45

8.3 Leakage Test 47

8.4 Servicing

the Carburetor 47

8.4.1 Metering Diaphragm /

Manual Fuel Pump 47

8.4.2 Inlet Needle 49

8.4.3 Pump Diaphragm 49

8.4.4 Throttle Lever /

Rotary Knob 51

8.4.5 Adjusting Screws 52

8.5 Adjusting

the Carburetor 54

8.5.1 Basic Setting 54

8.5.2 Standard Setting 55

8.6 Removing and

Installing Throttle Cable

(Loop Handle) 56

8.6.1 Removing and

Installing Throttle Cable

(Bike Handle) 58

8.6.2 Adjusting the

Throttle Cable 58

8.7 Removing and

Installing the Spacer

Flange 59

8.8 Tank Vent 60

8.8.1 Testing 60

8.8.2 Removing and

Installing 61

8.9 Fuel Intake 61

8.9.1 Pickup Body 61

8.9.2 Fuel Hoses 62

8.9.3 Fuel Tank Cap 63

8.10 Removing and

Installing the Engine

Housing 64

9. Drive Tube 65

9.1 Removing and

Installing 65

9.1.1 Disassembling

(KM 56) 66

9.1.2 Disassembling

(FC 56) 68

9.1.3 Disassembling

(FS 56) 69

9.1.4 Disassembling

(FS 40, 50) 70

9.1.5 Removing and

Installing the

Bearing Housing 71

9.1.6 Loop Handle 72

9.1.7 Loop Handle with

Barrier Bar 73

9.2 Add-On Components 74

9.2.1 Deflector for Machines

without Gearbox 74

9.2.2 Deflector for Machines

with Gearbox 74

9.2.3 One-part

Carrying Ring 75

9.2.4 Retainer 75

9.3 Gearbox 75

10. Special

Servicing Tools 76

11. Servicing Aids 77

Contents

2Series 4144 Components FC, FS, KM

1. Introduction

This service manual contains

detaileddescriptions of alltherepair

andservicingproceduresspecific to

this power tool.

You should make use of the

illustrated parts lists while carrying

out repair work. They show the

installed positions of the individual

components and assemblies.

Refer to the latest edition of the

relevant parts list to check the part

numbers of any replacement parts.

A fault on the machine may have

several causes. To help locate the

fault, consult the troubleshooting

charts for all assemblies and

systems in this manual and the

"STIHL Service Training System".

Refer to the “Technical Information”

bulletins for engineering changes

which have been introduced since

publication of this service manual.

Technical information bulletins also

supplement the parts list until a

revised edition is issued.

The special tools mentioned in the

descriptionsarelistedinthechapter

on "Special Servicing Tools" in this

manual. Use the part numbers to

identify the tools in the

"STIHL Special Tools" manual. The

manual lists all special servicing

tools currently available from

STIHL.

Symbolsareincludedinthetextand

pictures for greater clarity.

The meanings are as follows:

In the descriptions:

:= Action to be taken as

showninthe illustration above

the text

– = Action to be taken that is

not shown in the illustration

above

the text

In the illustrations:

APointer

aDirection of movement

@4.2 = Reference to another

chapter, i.e. chapter 4.2

in this example

Service manuals and all technical

information bulletins are intended

exclusively for the use of properly

equipped repair shops. They must

not be passed to third parties.

Always use original STIHL

replacement parts.

They can be identified by the STIHL

part number,

the {

logo and the

STIHL parts symbol K

This symbol may appear alone on

small parts.

Storing and disposing of oils and

fuels

Collect fuel or lubricating oil in a

clean container and dispose of it

properly in accordance with local

environmental regulations.

3Series 4144 Components FC, FS, KM

2. Safety Precautions

If the engine is started up in the

course of repairs or maintenance

work, observe all local and country-

specific safety regulations as well

as the safety precautions and

warnings in the instruction manual.

Gasolineisanextremelyflammable

fuel and can be explosive in certain

conditions.

Always wear suitable protective

gloves for operations in which

components are heated for

assembly or disassembly.

Improper handling may result in

burns or other serious injuries.

Do not smoke or bring any fire,

flame or other source of heat near

the fuel. All work with fuel must be

performed outdoors only. Spilled

fuel must be wiped away

immediately.

Always perform leakage test after

working on the fuel system and the

engine.

4Series 4144 Components FC, FS, KM

3. Specifications

3.1 Engine

FS 40 FS 50, 56, FC 56, KM 56

Displacement: 27.2 cm327.2 cm3

Bore: 34 mm 34 mm

Stroke: 30 mm 30 mm

Engine power to ISO 8893: 0.7 kW (1.0 bhp)

at 8,500 rpm 0.8 kW (1.1 bhp)

at 8,500 rpm

Max. permissible speed

(with cutting attachment): 10,000 rpm 10,000 rpm

Idle speed: 2,800 rpm 2,800 rpm

Clutch: Centrifugal clutch without

linings Centrifugal clutch without

linings

Clutch engages at: 4,200 rpm 4,200 rpm

Crankcase leakage test

at gauge pressure: 0.5 bar

under vacuum: 0.5 bar

3.2 Fuel System

Carburetor leakage test at

gauge pressure: 0.3 bar

Operation of tank vent at

gauge pressure: 0.5 bar

Fuel: as specified in instruction

manual

3.3 Ignition System

Air gap between ignition

module and fanwheel: 0.30 mm

Spark plug (suppressed): NGK CMR6H

NGK 6H

Bosch WSR 6 F

Electrode gap: 0.5 mm

5Series 4144 Components FC, FS, KM

3.4 Tightening Torquese

DG and P (Plastoform) screws are used in polymer and light metal components. These screws form a

permanent thread when they are installed for the first time. They can be removed and installed as often as

necessary without impairing the strength of the screwed assembly, providing the specified tightening torque is

observed.

For this reason it is essential to use a torque wrench.

Fastener Thread size For component Torque

Remarks

Screw P 6x14 Line limiting blade/deflector 2.5

Screw M 5x30 Control handle/handle/nut with washer 2.0

Screw P 5x14 Filter cover/filter housing 3.0

Nut M 5 Filter housing/carburetor/spacer flange 3.5

Screw P 4x12 Throttle cable/engine housing 1.5

Screw D 6x28 Gearbox/drive tube clamp (FS 56) 12.0

Screw D 5x20 Shroud/cylinder 6.0

Screw M 6x35 Clamp/clamp block/clamp 4.5

Screw M 6x25 Clamp/loop handle 4.5

Screw P 5x20 Engine housing/shroud 4.0

Screw M 5x20 Engine housing/crankcase 7.0

Screw P 5x20 Engine housing torsion lock/drive tube 4.0

Screw M 5x14 Deflector/gearbox (FS 56) 4.5

Screw M 6x30 Deflector/drive tube/nut /FS 40,50) 5.0

Screw M 6x14 Clamp/drive tube/harness ring 4.5

Screw D 5x20 Starter cover/crankcase 6.0

Screw D 5x20 Starter cover/engine pan 6.0

Screw M 4x9 End cover/carburetor 2.0

6Series 4144 Components FC, FS, KM

Remarks:

1) Loctite 242 or 243, medium strength

2) Loctite 270, high strength

3) Loctite 649, high strength

4) Loctite 272, high strength up to 250°C

5) Degrease crankshaft/flywheel and mount oil-free

Use the following procedure when refitting a DG or P screw in an existing thread:

Place the screw in the hole and rotate it counterclockwise until it drops down slightly.

Tighten the screw clockwise to the specified torque.

This procedure ensures that the screw engages properly in the existing thread and does not form a new thread

and weaken the assembly.

Coat micro-encapsulated screws with medium strength Loctite 242 or 243 before reinstalling.

Power screwdriver setting for polymer: DG and P screws max. 500 rpm

Do not use an impact wrench for releasing or tightening screws.

Do not mix up screws with and without binding heads.

7Series 4144 Components FC, FS, KM

4. Troubleshooting

4.1 Clutch

Condition Cause Remedy

Cutting attachment stops under

load at full throttle Clutch shoes badly worn Install new clutch

Clutch drum badly worn Install new clutch drum

Cutting attachment runs at idle

speed Engine idle speed too high Readjust idle speed screw LA

Clutch springs stretched or fatigued Replace the clutch springs or install

new clutch

Clutch spring hooks broken Replace the clutch springs

Loud noises Clutch springs stretched or fatigued Replace all clutch springs

Clutch shoe retainer broken Install new clutch

Clutch shoes and carrier worn Install new clutch

Condition Cause Remedy

8Series 4144 Components FC, FS, KM

4.2 Rewind Starter

Condition Cause Remedy

Starter rope broken Rope pulled out too vigorously as

far as stop or over edge, i.e. not

vertically

Fit new starter rope

Normal wear Fit new starter rope

Starter rope does not rewind Very dirty or corroded Clean rewind spring or replace rope

rotor

Insufficient spring tension Check rewind spring and increase

tension

Rewind spring broken Install new rope rotor

Starter rope cannot be pulled out

far enough Spring overtensioned Check rewind spring and reduce

tension

Starter rope can be pulled out

almost without resistance

(crankshaft does not turn)

Guide pegs on pawls or pawls

themselves are worn Fit new pawls

Spring clip on pawl fatigued Fit new spring clip

Starter rope is difficult to pull or

rewinds very slowly Starter mechanism is very dirty Thoroughly clean complete starter

mechanism

Lubricating oil on rewind spring

becomes viscous at very low

outside temperatures (spring

windings stick together)

Coat rewind spring with a little

standardsolvent-based degreasant

(containing no chlorinated or

halogenated hydrocarbons), then

pull rope carefully several times

until normal action is restored

9Series 4144 Components FC, FS, KM

4.3 Ignition System

Exercise extreme caution while

carrying out maintenance and

repair work on the ignition system.

The high voltages which occur can

cause serious or fatal accidents.

Condition Cause Remedy

Engine runs roughly, misfires,

temporary loss of power Spark plug boot is loose Press boot firmly onto spark plug

and fit new spring if necessary

Spark plug sooted, smeared with oil Clean the spark plug or replace if

necessary.

If sooting keeps recurring, check air

filter

Fuel/oil mixture

– too much oil Use correct mixture of fuel and oil

Incorrect air gap between ignition

module and flywheel Set air gap correctly

Flywheel cracked or has other

damage or pole shoes have turned

blue

Install new flywheel

Ignition timing wrong, flywheel out

of adjustment, key on crankshaft

has sheared off

Locate flywheel properly or install

new flywheel

Weak magnetization in flywheel Install new flywheel

Irregular spark Check operation of switch shaft/

contact springs and ignition

module.

Faulty insulation or break in ignition

lead or short circuit wire. Check

ignition lead/ignition module and

replace ignition module if

necessary.

Check operation of spark plug.

Clean the spark plug or replace if

necessary.

Crankcase damaged (cracks) Install new crankcase

10 Series 4144 Components FC, FS, KM

Condition Cause Remedy

No spark Spark plug faulty Install new spark plug

Faulty insulation or short in short

circuit wire Check short circuit wire for short

circuit to ground

Break in ignition lead or insulation

damaged Check ignition lead, replace ignition

module if necessary

Ignition module faulty Install new ignition module

11Series 4144 Components FC, FS, KM

4.4 Carburetor

Condition Cause Remedy

Carburetor floods; engine stalls Inlet needle not sealing

– foreign matter in valve seat or

cone

Remove and clean the inlet needle,

clean the carburetor

Inlet control lever sticking on

spindle Check inlet control lever, replace if

necessary

Helical spring not located on nipple

of inlet control lever Remove the inlet control lever and

refit it correctly

Perforated disc on diaphragm is

deformed and presses constantly

against the inlet control lever

Fit a new metering diaphragm

Metering diaphragm deformed Fit a new metering diaphragm

Poor acceleration Setting of low speed screw too lean Check basic carburetor setting,

correct if necessary

Setting of high speed screw too

lean Check basic carburetor setting,

correct if necessary

Inlet needle sticking to valve seat Remove inlet needle, clean and

refit

Diaphragm gasket leaking Fit new diaphragm gasket

Metering diaphragm damaged or

shrunk Fit a new metering diaphragm

Tank vent faulty Replace tank vent

Leak in fuel hose between tank and

fuel pump Install new hose

12 Series 4144 Components FC, FS, KM

Condition Cause Remedy

Engine will not idle, idle speed too

high Throttle shutter opened too wide by

idle speed screw LA Reset idle speed screw LA

correctly

Oil seals/crankcase leaking Seal or replace oil seals/crankcase

Engine stalls at idle speed Idle jet bores

or ports blocked Clean the carburetor

Setting of low speed screw too rich

too lean

Reset low speed screw Lcorrectly

Setting of idle speed screw LA

incorrect – throttle shutter

completely closed

Reset idle speed screw LA

correctly

Tank vent faulty Replace tank vent

Leak in fuel hose between tank and

fuel pump Install new hose

13Series 4144 Components FC, FS, KM

Condition Cause Remedy

Engine speed drops quickly under

load – low power Air filter dirty Clean air filter or replace if

necessary

Throttle shutter not opened fully Check throttle cable and cable

adjustment and readjust if

necessary

Tank vent faulty Replace tank vent

Fuel pickup body dirty Install new pickup body

Fuel strainer dirty Clean fuel strainer in carburetor,

replace if necessary

Leak in fuel hose between tank and

fuel pump Install new hose

Setting of high speed screw Htoo

rich Check basic carburetor setting,

correct if necessary

Main jet bores or ports blocked Clean the carburetor

Pump diaphragm damaged or

fatigued Fit new pump diaphragm

Ignition timing wrong, flywheel out

of adjustment, key on crankshaft

has sheared off

Locate flywheel properly or install

new flywheel

14 Series 4144 Components FC, FS, KM

4.5 Engine

Always check and, if necessary,

repair the following parts before

looking for faults on the engine:

- Air filter

- Fuel system

- Carburetor

- Ignition system

Condition Cause Remedy

Engine does not start easily, stalls

at idle speed, but operates normally

at full throttle

Oil seals in crankcase damaged Replace the oil seals

Crankcase leaking or damaged

(cracks) Seal or replace the crankcase

Engine does not deliver full power

or runs erratically Piston ring worn or broken Fit new piston ring

Muffler / spark arresting screen

carbonized Clean the muffler (inlet and

exhaust), replace spark arresting

screen, replace muffler if necessary

Air filter dirty Replace air filter

Fuel hose kinked or torn Fit new hose or position it free from

kinks

Engine overheating Insufficient cylinder cooling. Air

inlets blocked or cooling fins on

cylinder very dirty

Thoroughly clean all cooling air

openings and the cylinder fins

15Series 4144 Components FC, FS, KM

5. Engine

5.1 Removing and Installing

– Remove the drive tube, b9.1

– Remove the rewind starter,

b6.2

:Take out the screw (arrow).

– Remove the filter cover (1).

:Take out the screw (arrow).

:Pull boot (1) off the spark plug.

545RA025 TG

545RA026 TG

:Pull the protective cap (1) off the

spark plug boot (2).

– Push the boot on to the spark

plug.

– Turn the machine over.

:Take out the screws (arrows).

– Turn the machine over

:Remove the shroud (1).

938RA087 TG545RA027 TG545RA028 TG

:Disconnect the short circuit wire

(1) and ground wire (2).

:Disconnectthe tankventhose(1)

from the filter housing (arrow).

:Disconnect the fuel return hose

(2) and fuel suction hose (1) from

the stubs (arrows).

– Install new fuel hoses, b8.9.2

545RA029 TG

545RA030 TG545RA031 TG

16 Series 4144 Components FC, FS, KM

– Press down the throttle lever until

the nipple (arrow) projects.

:Turn the pin (2) until the slot is in

line with the throttle cable (1).

– Remove the throttle cable (1).

– Turn the machine over.

:Take out the screws (arrows).

– Turn the machine over again and

lift the engine out.

545RA032 TG

545RA033 TG

:Remove the air baffle (1).

– Inspect the muffler and replace if

necessary, b5.8

– Check the air filter, carburetor

and spacer flange, replace as

necessary, b8.1, b8.2, b8.7

– Troubleshooting, b4.4, b4.5

Allotheroperationsare describedin

the service manual for the "Series

4144 Powerhead".

5.2 Leakage test