STIH)

STIHL Series 4140 Components BG, SH 2005-01

q© ANDREAS STIHL AG & Co. KG, 2005

Contents

1. Introduction 2

2. Safety Precautions 3

3. Specifications 4

3.1 Fuel System 43.2 Tightening Torques 5

4. Troubleshooting 7

4.1 Rewind Starter 74.2 Fuel System 84.3 Engine 10

5. Housing 11

5.1 Handle Molding 115.2 Handle and Feet

(BG 85, SH 85) 11

6. Engine 12

6.1 Removing and Installing 12

6.2 Muffler/Spark Arresting Screen 13

6.2.1 Without Cat 136.2.2 Muffler with

Catalytic Converter 13

7. Rewind Starter 14

7.1 General 147.2 Removing and

Installing 147.3 Starter Cup 157.4 Rope Rotor 157.5 Replacing the

Rewind Spring 167.5.1 Tensioning the

Rewind Spring 177.6 Starter Rope 177.7 Pawl 18

Series 4140 Components BG, SH

8. Throttle Control 18

8.1 Throttle Trigger 188.2 Setting Lever

(BG 85, SH 85 only) 198.3 Stop Switch 198.3.1 Version up to 2001 198.3.2 Version from 2001 208.4 Short Circuit Wire/

Ground Wire 208.5 Throttle Cable 218.6 Throttle Rod 21

9. Fuel System 21

9.1 Air Filter 219.1.1 Removing and

Installing 229.1.2 Choke Shutter 229.2 Carburetor 239.2.1 Leakage Test 239.2.2 Removing and

Installing 249.2.3 Spacer Flange 249.3 Servicing

the Carburetor 259.3.1 Manual Fuel Pump

with Oval End Cover 259.3.2 Manual Fuel Pump

with Square End Cover 26

9.3.3 Metering Diaphragm 269.3.4 Inlet Needle 279.3.5 Fixed Jet 289.3.6 Pump Diaphragm

and Fuel Strainer 289.4 Adjusting

the Carburetor 299.4.1 Carburetor

with LD Screw 299.4.2 User Adjustment of

Carburetor with H, L and LA Screws 29

9.4.3 Basic Setting on Carburetor with H, L and LA Srews 31

9.5 Tank Vent 329.5.1 General 329.5.2 Replacing 339.6 Fuel Tank 339.6.1 General 339.6.2 Pickup Body 349.6.3 Fuel Hoses 34

10. Blower and Vacuum Attachment 35

10.1 Fanwheel 3510.2 Protective Screen

(all except BG 45) 3510.3 Protective Screen

(BG 45 only) 3510.4 Blower Tube

(BG only) 3610.5 Suction Tube

(SH only) 3610.6 Elbow (SH only) 36

11. Special Servicing Tools 37

12. Servicing Aids 38

1

This service manual contains detailed descriptions of all typical repair and servicing procedures for models BG 45, 46, 55, 65, 85, SH 55, 85, which are based on the series 4140 powerhead.

You will find detailed descriptions of procedures for servicing and repairing engine components in the service manual for the “Series 4140 Powerhead“.

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 chapter on "Troubleshooting" in this manual and the "STIHL Service Training System" for all assemblies.

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.

2

The special servicing tools mentioned in the descriptions are listed in the chapter "Special Servicing Tools" of 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.

Symbols are included in the text and pictures for greater clarity.The meanings are as follows:

In the descriptions:

: = Action to be taken as shown in the illustration (above the text)

– = Action to be taken that is

not shown in the illustration (above the text)

b 4.2Reference to another chapter, i.e. chapter 4.2 in this example.

In the illustrations:

A Pointer

aDirection of movement

Service manuals and 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 theSTIHL part number,the STIH) logo and theSTIHL parts symbol (This symbol may appear alone on small parts.

1. Introduction

Series 4140 Components BG, SH

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.

Gasoline is an extremely flammable fuel and can be explosive in certain conditions.

Improper handling may result in burns or other serious injuries.

Warning!Do not bring any fire, flame, spark or other source of heat near the fuel. All work with fuel must be performed outdoors only. Spilled fuel must be wiped away immediately.

Series 4140 Components BG, SH

2. Safety Precautions

3

3. Specifications

3.1 Fuel System Carburetor: Diaphragm carburetorCarburetor leakage testat gauge pressure: 0.8 bar (8 kPa)Operation of tank vent at gauge pressure: 0.3 bar (3 kPa)under vacuum: 0.05 bar (0.5 kPa)Fuel: see instruction manualOctane number: min. 90 RONFuel mixture: Regular brand-name gasoline and

STIHL 50:1 two-stroke engine oil or brand-name two-stroke engine oil

Mix ratio: 50:1 with STIHL 50:1 two-stroke engine oil

Fuel mix for units with catalytic converter: Use only STIHL 50:1 two-stroke engine oil with unleaded gasoline.

4 Series 4140 Components BG, SH

3.2 Tightening Torques

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

Nm

Screw IS-DG5x60 Muffler/cylinder 9.0Screw IS-DG5x24 Muffler/cylinder (version with catalytic

converter)9.0

M14x7 Stub/muffler (version with spark arresting screen in muffler)

10.0

Screw IS-DG5x24 Spacer flange/cylinder 6.0 1)Collar screw P6x15/49 Collar screw/inner blower housing 4.0 2)Screw IS-DG5x24 Inner blower housing/crankcase 8.0Screw IS-DG5x24 Inner blower housing/engine pan 8.0Screw IS-P6x26.5 Outer/inner blower housings 5.0Nut M8x1LH-06 Fanwheel/crankshaft

(SH with shredder blade)17.0

Screw IS-P6x19 Handle/inner blower housing 5.0 3)Screw IS-P6x19 Handle molding/inner blower housing 4.0 4)Screw IS-P6x19 Fan housing/inner blower housing 6.0Screw IS-DG5x20Z Fan housing/spiral housing 6.0Screw IS-DG5x24 Spiral housing/crankcase 6.0Screw IS-DG5x24 Spiral housing/engine pan 6.0Screw IS-P6x19 Protective screen/outer blower housing 5.0 5)

M14x1.25 Spark plug 20.0

Remarks:

1) with binding head2) SH 55, 85 only3) BG 85, SH 85 only4) BG 65, 85, SH 85 only5) BG 45 only

5Series 4140 Components BG, SH

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.

Power screwdriver settings for polymer:

Plastoform screws max. 600 rpm

DG screws max. 500 rpm

Important: Do not mix up screws with and without binding head

6 Series 4140 Components BG, SH

4. Troubleshooting4.1 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

Rewind spring broken Spring overtensioned – no reserve when rope is fully extended

Fit new rewind spring

Very dirty or corroded Fit new rewind spring

Starter rope can be pulled out almost without resistance (crankshaft does not turn)

Guide peg on pawl or pawl itself is worn

Fit new pawl

Spring clip fatigued Fit new spring clip

Starter rope is difficult to pull and rewinds very slowly

Starter mechanism very dirty (dusty conditions)

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 standard solvent-based degreasant (containing no chlorinated or halogenated hydrocarbons). Then pull rope carefully as often as necessary until normal action is restored

7Series 4140 Components BG, SH

4.2 Fuel System

Condition Cause Remedy

Engine stalls at idle speed Idle jet bores or ports blocked Clean jet bores and ports and blow clear with compressed air

Idle jet too rich or too lean Reset low speed screw (L) correctly

Setting of idle speed screw (LA) incorrect – throttle shutter completely closed

Reset idle speed screw (LA) correctly

Engine speed drops quickly under load – low power

Air filter plugged Clean the air filter or replace if necessary

Tank vent faulty Fit new tank vent

Leak in fuel line between tank and fuel pump

Seal or renew connections and fuel line

Pump diaphragm damaged or fatigued

Fit new pump diaphragm

Main jet bores or ports blocked Clean the bores and ports

Fuel pickup body dirty Install new pickup body

Setting of high speed screw (H) too rich

Reset high speed screw (H) correctly

Throttle shutter not opened fully Check linkage

8 Series 4140 Components BG, SH

Condition Cause Remedy

Poor acceleration Idle jet too lean Turn low speed screw (L) counter-clockwise (richer), no further than stop

Main jet too lean Turn high speed screw (H) counter-clockwise (richer), no further than stop

Inlet control lever too low(relative to correct installed position)

Set inlet control lever flush with top of carburetor body

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

Connecting bore to atmosphere blocked

Clean the bore

Diaphragm gasket leaking Fit new diaphragm gasket

Metering diaphragm damaged or shrunk

Fit new metering diaphragm

Engine will not idle –idle speed too high

Throttle shutter opened too wide by idle speed screw (LA)

Reset idle speed screw (LA) correctly

Carburetor floods, engine stalls

Inlet needle not sealing. Foreign matter in valve seat or cone damaged

Remove and clean or replace inlet needle, clean fuel tank, pickup body and fuel line if necessary

Inlet control lever sticking on spindle

Free off inlet control lever

Helical spring not located on nipple of inlet control lever

Remove inlet control lever and refit correctly

Perforated disc on diaphragm is deformed and presses constantly against inlet control lever

Fit new metering diaphragm

Inlet control lever too low(relative to correct installed position)

Fit new inlet control lever

9Series 4140 Components BG, SH

4.3 Engine

Always check and, if necessary,

repair the following parts before looking for faults on the engine:

– Air filter– Fuel system– Carburetor– Ignition system1)

Condition Cause Remedy

Engine does not start easily, stalls at idle speed, but operates normally at full throttle

Oil seals in crankcase faulty Install new oil seals 1)

Crankcase leaking / damaged (cracks)

Seal / replace the crankcase 1)

Muffler leaking Seal / replace the muffler

Engine does not deliver full power or runs erratically

Piston rings worn or broken Install new piston rings 1)

Muffler / spark arresting screen carbonized

Clean muffler (inlet and exhaust openings), replace spark arresting screen

Air filter element dirty Fit new air filter element

Fuel / impulse line kinked or cracked

Fit new lines or position without kinks

Engine overheating Insufficient cylinder cooling.Air inlets in fan housing blocked or cooling fins on cylinder very dirty

Thoroughly clean all cooling air passages and cooling fins

1) see "Series 4140 Powerhead" service manual

10 Series 4140 Components BG, SH

Remove fan housing with rewind starter, b 7.2

– Remove the spark plug.

BG 45, 55, SH 55 only

: Take out the screws (1) and remove the handle molding (2).

2

1

1

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BG 65, 85, SH 85 only

: Take out the screws (1) and remove the handle molding (2).

Note:BG 65 has no setting lever.

2

1

1

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Series 4140 Components BG, SH

: If necessary, replace the setting lever (1), b 8.2

: If necessary, remove the grip molding (2) as follows:

2

1

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2

: Pull the grip molding (1) out of the guides (arrows) and lift it away.

Install in the reverse sequence.

1

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: Take out the screws (arrows).

– Remove the handle.

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: Pull the feet (1) upwards and out of the handle.

Reassemble in the reverse sequence.

1

1

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5. Housing5.1 Handle Molding

5.2 Handle and Feet(BG 85, SH 85)

11

– Remove fan housing with rewind starter, b 7.2

– Remove the fanwheel, b 10.1

– Remove the filter housing, b 9.1

– Remove the handle molding, b 5.1

: Disconnect the short circuit wire (1) and ground wire (2) from the ignition module.

: Remove the retainers (3).

2

1

3

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: Pull the fuel hoses (1 and 2) off the elbow connectors on the carburetor.

21

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4

12

: On machines with a throttle cable, disconnect the throttle cable (1) from slotted pin (2) on the throttle lever and push the throttle cable out of the tensioner (arrow). If necessary, remove the carburetor first. Avoid kinking the throttle cable in this process.

21

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5

– On machines with a throttle rod, remove the throttle rod, b 8.6

: Take engine mounting screws (arrows) out of inner fan housing.

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2

: Remove the engine.

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Install in the reverse sequence. Observe correct tightening torques, b 3.2.

: When installing the engine in the inner fan housing, check that the gasket (arrow) is in front of the inner fan housing.

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7

6. Engine6.1 Removing and Installing

Series 4140 Components BG, SH

Troubleshooting, b 4.3

– Remove the fan housing with rewind starter, b 7.2

6.2.1 Without Cat

Muffler

: Take out the screws (1).

1

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: Remove the muffler (1) and exhaust gasket (2).

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1

2

1

Series 4140 Components BG, SH

Install in the reverse sequence.

– Clean the sealing faces before installation.

– Install a new exhaust gasket.

– Apply sealant to the underside of the screw head, b 12.

– Tighten down the screws firmly, b 3.2

Spark arresting screen

: On machines with a removable stub (1) (with and without spark arresting screen), use a 15 mm wrench to unscrew the stub.

– Clean the spark arresting screen

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1

or install a new stub if necessary.

– Clean the thread of the stub and coat it with sealant, b 12.

Follow the sealant manufacturer’s instructions.

– Screw home the stub and tighten it down firmly, b 3.2

Troubleshooting, b 4.3

The catalytic converter integrated in the muffler is a device that helps reduce the amount of noxious emissions in the exhaust gas by initiating chemical reactions without being consumed in the process. The catalytic converter is maintenance-free. Never attempt to carry out repairs on the catalytic converter.

Muffler

– Remove the fan housing with the rewind starter, b 7.2

: Take the screws (1) out of the muffler.

1

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8

: Remove the muffler (1) with exhaust gaskets (2) and flange (3).

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9

2

1

3

6.2 Muffler/Spark Arresting Screen

6.2.2 Muffler with Catalytic Converter

13

Install in the reverse sequence.

– Clean the sealing faces before installation.

– Install new exhaust gaskets.

Spark arresting screen

– Remove the fan housing with rewind starter, b 7.2

: Take out the screw (1).

: Pull the spark arresting

2

1

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screen (2) out of the muffler.

– Clean the spark arresting screen, replace it if necessary.

Install in the reverse sequence.

14

Troubleshooting, b 4.1

If the action of the starter rope becomes very stiff and the rope rewinds very slowly or not completely, it can be assumed that the starter mechanism is in order but plugged with dirt. At very low outside temperatures the lubricating oil on the rewind spring may thicken and cause the spring windings to stick together. This has a detrimental effect on the function of the starter mechanism. In such a case it is sufficient to apply a few drops of a standard solvent-based degreasant (containing no chlorinated or halogenated hydrocarbons) to the rewind spring.Carefully pull out the starter rope several times and allow it to rewind

until its normal smooth action is restored.

If clogged with dirt or pitch, the entire starter mechanism, including the rewind spring, must be removed and disassembled. Take particular care when removing the spring.

Clean all parts, b 12.

Lubricate the rewind spring and starter post with STIHL special lubricant, b 12, before installing.

: Take out the screws (1+2).

– Remove the fan housing with rewind starter.

: If necessary, remove the antistatic wire (arrow).

7. Rewind Starter7.1 General

7.2 Removing and Installing

Series 4140 Components BG, SH

Machines with starter cup integrated in flywheel: For servicing information see the chapter on “Flywheel” in the “Series 4140 Powerhead” service manual.

Series 4140 Components BG, SH

Remove the rewind starter, b 7.2

Relieving tension of rewind spring

The rewind spring will not be under tension if the starter rope is broken.

– Pull out the starter rope about 10 cm and hold the rope rotor steady.

– While still holding the rotor steady, take three turns of the rope off the rotor.

– Pull out the starter rope a little further and then let go of the rotor.

The rotor spins back so that the rewind spring is no longer under tension.

Removing

The rewind spring must not be under tension.

: Remove the spring clip (1) from the starter post.

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132

: Remove the washer (2) and

pawl (3).

– Carefully pull the rope rotor off the starter post.

– Replace the broken or worn starter rope, b 7.6

Installing

– Coat the bore in the rope rotor with STIHL special lubricant, b 12.

: Fit the rotor on the starter post so that the driver (1) on the rope rotor slips behind the inner spring loop (2).

21

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7.3 Starter Cup

7.4 Rope Rotor

15

– Check that the spring loop has engaged by turning the rope rotor a little and letting it go. It must spring back.

– Coat pawl with special lubricant and install, b 12.

: Fit the washer and engage the spring clip (1) in the groove in the starter post.

: Make sure the spring clip (1) den engages the guide peg (arrow) on the pawl (2) and points clockwise.

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3

12

Handle the spring clip with care. The rewind starter may not function properly if the spring clip is deformed.

– Tension the rewind spring, b 7.5.1

– Install the rewind starter, b 7.2

16

– Remove the rope rotor, b 7.4

– Remove the pieces of broken spring from the rope rotor and starter cover.

– Before installing, lubricate the new spring with a few drops of STIHL special lubricant, b 12.

: Position the rewind spring in the starter and press the outer spring loop over the lug (arrow).

The rewind spring may pop out and uncoil if the rope rotor is not installed very carefully.

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4

If the rewind spring has popped out,

refit it as follows:

– Hold the spring in your hand and wind from the inside outwards and tension it to a diameter of 55 mm.

: Then grip the rewind spring with pointed nose pliers about 10 mm from the end of the outer loop and place it in the starter.

: Check the distance of the inner spring loop from the hub and correct if necessary. Dimension "A" must not be more than 2 mm.

– Install the rope rotor, b 7.4

– Tension the rewind spring, b 7.5.1

7.5 Replacing the Rewind Spring

Series 4140 Components BG, SH

: Make a loop in the unwound starter rope. Grip the rope close to the rotor and use it to turn the rotor six full turns clockwise.

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: Hold the rope rotor steady.

: Pull out the rope with the starter grip and straighten it out.

– Hold the starter grip firmly to keep the rope tensioned.

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8

– Let go of the rope rotor and

slowly release the starter grip so that the rope winds itself onto the rotor.

Series 4140 Components BG, SH

The starter grip must sit firmly in the rope guide bush without drooping to one side. If this is not the case, tension the spring by one additional turn.

When the starter rope is fully extended, it must still be possible to

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rotate the rope rotor at least another

half turn before maximum spring tension is reached. If this is not the case, pull the rope out, hold the rope rotor steady and take off one turn of the rope.

Do not overtension the rewind spring as this will cause it to break.

– Place the rewind starter in position, insert the screws and tighten them down firmly, b 3.2

– Remove the rewind starter, b 7.2

– If the starter rope is broken, remove the remaining rope from the rope rotor and starter grip.

– If the starter rope is worn, relieve tension of rewind spring, b 7.4. Pull the end of the rope out of the rotor and undo the knot. Then pull the worn rope out of the starter grip, housing and rotor.

: Thread one end of the new rope through the rotor and housing. Tie a simple overhand knot in the end of the rope.

– Pull the rope back into the rotor until the knot locates in the recess.

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– Thread the other end of the rope through the starter grip. Tie a simple overhand knot in the end of the rope.

7.5.1 Tensioning the Rewind Spring

7.6 Starter Rope

17

: On machines with "ElastoStart": Thread end of new starter rope through the grip (1) and the spring element (2). Tie a simple overhand knot in the end of the rope. Pull the rope and spring element into the grip and then fit the cap (3).

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5

3

1 2

– Tension the rewind spring, b 7.5.1

– Install the rewind starter, b 7.2

18

– Remove the rewind starter, b 7.2

: Ease the spring clip (1) off the starter post and pull the pawl (2) out of the rope rotor.

Do not pull the rope rotor off the

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12

starter post.

– Coat the new pawl with special lubricant, b 12, and fit it in position.

: Push the spring clip (1) into the groove in the starter post.

: Make sure the spring clip (1) engages the guide peg (arrow) on the pawl (2).

The spring clip must point clockwise.

Handle the spring clip with care. The rewind starter may not function properly if the spring clip is deformed.

– Install the rewind starter, b 7.2

– Remove the handle molding, b 5.1

: On machines with a throttle cable, remove the throttle trigger (1) and disconnect it from the throttle cable.

: On machines with a throttle rod (1), remove the throttle trigger (2) and disconnect it from the throttle rod.

Install in the reverse sequence.

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8

1

2

7.7 Pawl

8. Throttle Control8.1 Throttle Trigger

Series 4140 Components BG, SH

– Remove the handle molding, b 5.1

: Ease the E-clip (8) off the setting lever’s stub.

: Remove the cam (7).

8

5

7

124

6

3

4 3

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: Pull the setting lever (1) with

washers (2, 5) and cup springs (3, 4) out of the handle molding (6).

Reassemble in the reverse sequence.

– Slip the washers (2, 5) and cup springs (3, 4) over the stub of the setting lever (1) and push it into the handle molding (6).

Note the correct installed position of the two cup springs (3 and 4).

Series 4140 Components BG, SH

: Fit the cam (1) on the setting lever’s stub so that it lines up with the marking on the handle housing.

: Push the E-clip (2) in the groove on the setting lever’s stub.

1

2

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7

Assemble all other parts in the

reverse sequence.

: Use a flat screwdriver to ease the stop switch (1) out of the handle molding.

: Pull the connectors (2) (short circuit and ground wires) off the stop switch.

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3

2

1

Install in the reverse sequence.

Check correct positions of wires.

8.2 Setting Lever (BG 85, SH 85 only)

8.3 Stop Switch8.3.1 Version up to 2001

19

– Remove the handle molding, b 5.1

: Use a flat screwdriver to ease the stop switch (1) and protective cap (2) out of the handle molding.

: Pull the connectors (3) (short

3

21

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3

circuit and ground wires) off the

stop switch.

Install in the reverse sequence.

Check correct positions of wires.

20

– Remove the handle molding, b 5.1

– Remove the stop switch, b 8.3

: Pull the connectors of the short circuit wire (1) and ground

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1

2

1

wire (2) off the ignition module.

BG 45, 55, SH 55 only, from 2001

– Remove the throttle trigger, b 8.1

: Remove the wire (1) from the throttle trigger’s pivot pin (2).

2

1

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BG 65, 85, SH 85 from 2001 only

: Remove the wire (1) from the housing peg.

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1

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All BG/SH units

: Pull the retainers (1) off the ignition lead.

: Take the wires out of the guides (arrows) in the inner fan housing.

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Reassemble in the reverse

sequence.

– Push home the wires so that they are properly seated in the guides in the inner fan housing.

8.3.2 Version from 2001

8.4 Short Circuit Wire/Ground Wire

Series 4140 Components BG, SH

– Remove the handle molding, b 5.1

: Disconnect the throttle cable (1) from the throttle trigger (2), b 8.1

: Take the throttle cable out of the guides (arrows) in the inner fan

housing.

– Remove the carburetor, b 9.2.2

: Push the throttle cable (1) out of the tensioner (2). Remove the throttle cable.

Install in the reverse sequence.

Series 4140 Components BG, SH

– Remove the handle molding, b 5.1

: Remove the throttle trigger (2) and disconnect the throttle rod (1).

: Disconnect the throttle rod (1)

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8

1

2

from the carburetor.

Install in the reverse sequence.

Dirty air filters reduce engine power, increase fuel consumption and make starting more difficult.

If there is a noticeable loss of engine power, check to see if the air filter is plugged with dirt.

– Before removing the air filter, close the choke shutter and remove all loose dirt from around the filter.

– Wash the foam filter in a standard solvent-based degreasant containing no chlorinated or halogenated hydrocarbons and then dry. Replace if necessary.

– Replace the felt filter. As a temporary measure, knock the

filter out on the palm of your hand or blow clear with compressed air. Do not wash.

– Replace multi-ply felt filter. As a temporary measure, knock the filter out on the palm of your hand or blow clear with compressed air. Do not wash

If a felt filter is replaced by a multi-ply filter, do not re-install the foam filter.

Always replace a damaged air filter immediately.

8.5 Throttle Cable

8.6 Throttle Rod 9. Fuel System9.1 Air Filter

21

: Squeeze retainers together.

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: Swing the filter cover (1) to the side and pull the lugs out of the guides (arrows).

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1

: Pull the filter (1) out of the filter housing (3).

: Unscrew the nuts (2) and remove the filter housing.

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7

2

3

1

22

– Knock the filter out on the palm of your hand or blow clear with compressed air. Do not wash. Replace if heavily loaded.

Always replace a damaged air filter immediately.

Machines with catalytic converter

: Remove the gasket (1) and heat shield (2).

Use new gaskets.

Install in the reverse sequence.

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1

– Remove the air filter, b 9.1.1

: Remove the push nut (1).

: Pull the choke shutter (2) out of the lever (3).

– When installing, make sure the

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932R

A22

9

1

3

2

choke shutter is properly located

in the lever’s guide.

Use a new push nut.

Install in the reverse sequence.

9.1.1 Removing and Installing

9.1.2 Choke Shutter

Series 4140 Components BG, SH

If you suspect a fault in the fuel system, see b 4.2. In the case of problems with the carburetor or fuel supply system, also check or clean the tank vent, b 9.5The carburetor can be tested for leaks with the carburetor and crankcase tester 1106 850 2905.

– Remove the air filter, b 9.1.1

: Disconnect the fuel hose from the carburetor’s elbow connector.

VA

932R

A21

5

: Push the fuel line (1) 1110 141 8600 onto the nipple (2) 0000 855 9200.

VA

143R

A17

2

2 1

Series 4140 Components BG, SH

: Push the fuel line with nipple onto the carburetor’s elbow connector (arrow).

232R

A08

2V

A

: Connect the tester's pressure hose to the nipple.

VA

232R

A08

3

: Close the vent screw (1) on the rubber bulb (2) and pump air into the carburetor until the pressure gauge (3) shows a reading of approx. 0.8 bar.

VA

232R

A08

4

3

2

1

If this pressure remains constant, the carburetor is airtight. However, if it drops, there are two possible causes: 1. The inlet needle is not sealing (foreign matter in valve seat or sealing cone of inlet needle is damaged or inlet control lever sticking).

2. Metering diaphragm is damaged.

In either of these cases the carburetor has to be serviced.

– After completing the test, open the vent screw and pull the fuel line off the carburetor.

– Push the fuel hose onto the

carburetor’s elbow connector.

Assemble all other parts in the reverse sequence.

Always install a new gasket.

9.2 Carburetor 9.2.1 Leakage Test

23

Remove the air filter, b 9.1.1

: Disconnect the fuel hoses from from the elbow connectors on the carburetor.

VA

932R

A23

3

: On machines with throttle cable (1), disconnect throttle cable from slotted pin (2) on carburetor’s throttle lever.

– On machines with throttle rod, remove the throttle rod, b 8.6

21

VA

932R

A23

9

24

: Remove the carburetor (1) and gasket (2).

Install in the reverse sequence.

Always install the carburetor with new gaskets.

12

VA

932R

A23

4

Position the fuel hoses so that they

are not kinked.

Observe tightening torques, b 3.2

– Remove the carburetor, b 9.1.1

: On machines with throttle cable, pull the throttle cable (1) out of the spacer flange (2).

: On machines with throttle cable, take out the screws (1) and remove the spacer flange together with the hex head screws (2).

VA

932R

A25

3

12

: On machines with throttle rod, take out the screws (1) and remove the spacer flange together with the hex head screws (2).

VA

932R

A25

2

2

1

9.2.2 Removing and Installing

9.2.3 Spacer Flange

Series 4140 Components BG, SH

: Pull the gasket (1) out of the guides (arrows) on the spiral housing.

Install in the reverse sequence.

Always install new gaskets.

VA

932R

A25

4

Observe tightening torques,

b 3.2

Series 4140 Components BG, SH

– Carry out leakage test, b 9.2

– Remove the carburetor, b 9.2.2

: Take out the M3x12 screws (1).

: Remove the end cover with cap (2).

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936R

A22

3

1

2

: Take out the M3x8 screws (1).

: Remove the flange (2).

VA

936R

A22

4

1

2

: Take the cap out of the end cover.

VA

936R

A25

8

: Inspect the metering diaphragm and gasket and replace if necessary, b 9.3.3

Reassemble in the reverse sequence.

Additional holes in the gasket and

VA

936R

A02

5

diaphragm (if there are any) must

line up with those in the carburetor and flange.

9.3 Servicing the Carburetor9.3.1 Manual Fuel Pump with Oval End Cover

25

: Take out the screws (1).

– Remove the end cover with cap.

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936R

A02

3

1

: Take the cap out of the end cover.

VA

932R

A28

5

: Remove the flange.

VA

936R

A02

4

26

: Inspect the metering diaphragm and gasket and replace if necessary, b 9.3.3

Reassemble in the reverse sequence.

VA

936R

A02

5

– Remove flange from manual fuel pump with oval end cover, b 9.3.1

– Remove flange from manual fuel pump with square end cover, b 9.3.2

VA

936R

A02

6

1

2

: Remove the metering

diaphragm (1) and gasket (2) from the carburetor body.

If the gasket and diaphragm are stuck together, remove and separate them very carefully.

: Inspect the diaphragm and gasket and replace if necessary.

The diaphragm is a very delicate component. As a result of the alternating stresses the material eventually shows signs of fatigue, i.e. the diaphragm distorts and swells and has to be replaced.

Reassemble in the reverse sequence.

9.3.2 Manual Fuel Pump with Square End Cover

9.3.3 Metering Diaphragm

Series 4140 Components BG, SH

: Fit the gasket (1) on the carburetor body.

Line up the hole in the gasket (2) with the compensating bore in the carburetor.

VA

936R

A02

7

1

2

: Place metering diaphragm (1) on the gasket.

Line up the hole in the metering diaphragm (1) with the compensating bore in the carburetor and gasket.

VA

936R

A02

8

1

Assemble all other parts,

b 9.3.1 and 9.3.2.

Series 4140 Components BG, SH

– Remove the metering diaphragm, b 9.3.3

: Take out the screw (1).

936R

A02

9V

A

1

: Remove the inlet control lever (4), spindle (3), spring (2) and inlet needle (1).

Take care with the spring (2) because it may pop out during disassembly.

2

34

1

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932R

A26

0

: If there is an annular indentation (arrow) on the sealing cone of the inlet needle, it will be necessary to replace the inlet needle because it will no longer seal properly.

VA

372R

A12

0

Reassemble in the reverse sequence.

– Engage clevis in annular groove on head of the inlet needle.

Make sure the helical spring locates on the control lever’s nipple.

– Check that inlet control lever moves freely.

Important:The upper edge of the inlet control lever must be flush with the top of the carburetor body.

– Install the metering diaphragm, b 9.3.3

9.3.4 Inlet Needle

27

Take care not to damage the fixed jet when removing.

– Remove the metering diaphragm, b 9.3.3

C1Q-S48, C1Q-S50, C1Q-S55 carburetors only

: Unscrew the fixed jet (1).

VA

936R

A22

5

1

C1Q-S64, C1Q-S73 carburetors only

: Unscrew the fixed jet (1).

Reassemble in the reverse sequence.

936R

A03

1V

A

1

28

– Remove the carburetor, b 9.2.2

: Take out the screw (1).

: Remove the end cover (2).

VA

936R

A03

2

2

1

: Remove the gasket (1).

VA

936R

A03

3

1

: Remove the pump diaphragm (1).

If the gasket and pump diaphragm are stuck together, remove and separate them very carefully.

VA

936R

A03

4

1

The diaphragm is a very delicate component. As a result of the alternating stresses the material eventually shows signs of fatigue, i.e. the diaphragm distorts and swells and has to be replaced.

– Inspect the diaphragm and gasket and replace if necessary.

: Examine the fuel strainer (1) for contamination and damage and replace if necessary.

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936R

A08

6

1

Reassemble in the reverse sequence.

: The pump diaphragm (1) and gasket (2) are held in position by the pegs (arrows) on the end cover (3).

VA

932R

A25

9

3

2

1

9.3.5 Fixed Jet

9.3.6 Pump Diaphragm and Fuel Strainer

Series 4140 Components BG, SH

The carburetor with idle speed screw (LD) has no adjusting screws for maximum engine (H screw) or idle mixture (L screw).

The carburetor is tuned so that the engine receives an optimum fuel-air mixture under all operating conditions.

Standard setting

When adjusting from scratch, first carry out the standard setting.

Screw

: Carefully turn the idle speed screw (LD) (arrow) counterclockwise (left-hand thread) down onto its seat.

: Then turn the idle speed screw (LD) two full turns clockwise.

VA

232R

A09

0

LD

– Check the air filter and replace if necessary, b 9.1

– Check the spark arresting screen, clean or replace as necessary, b 7.2

Series 4140 Components BG, SH

Adjusting idle speed

– Carry out standard setting.

– Start the engine and warm it up.

Engine stops while idling:

VA

232R

A09

0

LD

: Turn the idle speed screw (LD) (arrow) slowly clockwise until the engine runs smoothly.

Erratic idling behavior, poor acceleration:

: Turn the idle speed screw (LD) slowly no more than half a turn counterclockwise.

Standard setting

The limiter cap must not be removed from the high speed screw (H) to carry out the standard setting.

With this carburetor it is only possible to correct the setting of the

VA

932R

A30

3

L

H

LA

high speed screw (H) within fine

LA Screws

limits.

– Check the air filter and replace if necessary, b 9.1.1

– Check the spark arresting screen, clean or replace it if necessary, b 6.2

9.4 Adjusting the Carburetor9.4.1 Carburetor with LD

9.4.2 User Adjustment of Carburetor with H, L and

29

Now make the following adjustments:

: Turn the high speed screw (H) counterclockwise as far as stop (no more than 3/4 turn)

: Carefully turn the low speed

VA

932R

A30

3

L

H

LA

screw (L) clockwise until it is

against its seat, then open it one full turn counterclockwise.

– Start the engine and allow it to warm up.

Fine tuning

A minor correction may be necessary when operating at high altitude or at sea level. Note that even very slight corrections to the high speed screw (H) produce a noticeable change in engine running behavior.

– Carry out the standard setting.

– Start the engine and allow it to

warm up.

– Open the throttle wide.

30

– At high altitude (mountains): Turn the high speed screw (H) clockwise (leaner), but no further than stop, until there is no noticeable increase in engine speed.

– At sea level: Turn the high speed screw (H) counterclockwise (richer), but no further than stop, until there is no noticeable increase in engine speed.

It is possible that the standard setting produces the highest engine rpm in both the above cases.

Adjusting idle speed

– Open the low speed screw (L)

one full turn.

– Allow the engine to warm up.

Engine stops while idling

– Turn the idle speed screw (LA) slowly clockwise until the engine runs smoothly.

Erratic idling behavior, poor acceleration

– Idle setting is too lean. Turn the low speed screw (L) counter-clockwise (about a quarter turn) until the engine runs and accelerates smoothly.

Erratic idling behavior

– Idle setting is too rich. Turn the low speed screw (L) clockwise (about a quarter turn) until the engine runs and accelerates smoothly.

It is usually necessary to change the setting of the idle speed screw (LA) after every correction to the low speed screw (L).

Series 4140 Components BG, SH

The limiter cap has to be removed from the high speed screw (H) only if it is necessary to replace the high speed screw (H), clean the carburetor or adjust it from scratch.

After removing the limiter cap it is necessary to carry out the basic setting.

and LA Srews

: On carburetors with a short limiter cap (1): Push the puller (2) 5910 890 4501, with the groove facing you, between the limiter cap (1) and carburetor body and pry the cap off. If the limiter cap is stuck on the screw, turn the puller over so that its groove faces the

VA

932R

A31

6

12

carburetor body. Pry off the

limiter cap.

Series 4140 Components BG, SH

: On carburetors with a long limiter cap (1):Use suitable pliers to pull off the limiter cap.

– Screw down both adjusting screw (H and L) clockwise until they are against their seats.

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932R

A31

5

1

Now make the following adjustments:

– Open the high speed screw (H) 1 1/2 turns counterclockwise.

– Open the low speed screw (L) one full turn counterclockwise.

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932R

A31

7

H L

Adjusting idle speed

– Check the air filter and clean or replace as necessary.

– Warm up the engine.

Adjust idle speed with a tachometer. Adjust specified engine speeds within a tolerance of +/- 200 rpm.

1. Adjust engine speed with idle speed screw (LA) to 3,300 rpm.

2.Turn low speed screw (L) clockwise or counterclockwise to obtain maximum engine speed.

If this speed is higher than 3,700 rpm, abort the procedure and

start again with step 1.

3. Use the idle speed screw (LA) to set engine speed again to 3,300 rpm

4. Set the engine speed to 2,800 rpm with the low speed screw (L).

5. Set maximum engine speed to 10,500 rpm with the high speed screw (H).

Do not re-install used caps because they may be damaged during the removal process. Always install a new limiter cap.

9.4.3 Basic Setting on Carburetor with H, L

31

: On carburetors with a short limiter cap:Line up the new cap for the high speed screw (H) against the rich stop and press it on only as far as the second noticeable detent position.

VA

249R

A12

9

270°

The stop limits the adjustment

range of the high speed screw (H) to a 3/4 turn. Do not press the cap against the carburetor body as it will otherwise be damage.

– Carry out standard setting, b 9.4.2

32

: On carburetors with a long limiter cap:Line up the new cap for the high speed screw (H) against the rich stop so that the high speed screw (H) can only be rotated a 3/4 turn clockwise.

VA

392R

A31

8

270

: Push on the limiter cap until it

butts against the carburetor body.

Carry out standard setting, b 9.4.2

Correct operation of the carburetor is only possible if atmospheric pressure and internal fuel tank pressure are equal at all times. This is ensured by the tank vent.In the event of trouble with the carburetor or the fuel supply system, always check the tank vent and replace it if necessary.

Testing the tank vent

– Open the tank cap slowly and drain the tank. Refit the tank cap, making sure it is tight.

– Disconnect the fuel hoses from the carburetor, b 9.2.2

– Seal one of the fuel hoses with a

suitable plug.

– Connect vacuum pump 0000 850 3501 to the other fuel hose and produce a vacuum in the fuel tank by operating the pump quickly.

– If the vacuum remains unchanged, install a new tank vent, b 9.5.2

If the vacuum slowly disappears, the tank vent is in order.

9.5 Tank Vent9.5.1 General

Series 4140 Components BG, SH

If no equalization of pressures takes place, replace the tank vent.

– Remove the filter housing, b 9.1.1

Note installed position of tank vent.

Machines up to 2002

: Pull out the tank vent (1).

: Pull out the grommet (2).

Install in the reverse sequence.

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932R

A09

6

2

1

Machines from 2002

: Carefully pry out the tank vent (1) with sealing ring (2).

VA

932R

A32

1

2

1

Series 4140 Components BG, SH

Always use a new sealing ring.

Install in the reverse sequence.

Fuel tank

The fuel tank is part of the inner fan housing and cannot be replaced separately.If the fuel tank is damaged, replace the complete inner fan housing.

The diaphragm pump draws fuel out of the tank and into the carburetor via the fuel hose. Any impurities mixed with the fuel are retained by the pickup body (filter). The fine pores of the filter eventually become clogged with minute particles of dirt. This restricts the passage of fuel and results in fuel starvation.

Always observe all safety precautions when working on the fuel system, b 2.

In the event of trouble with the fuel supply system, always check the fuel tank and the pickup body first. Clean the fuel tank if necessary.

Cleaning the fuel tank

– Unscrew the fuel filler cap and drain the tank.

– Pour a small amount of clean gasoline into the tank.

– Close the tank and shake the machine vigorously.

– Open the tank again and drain it.

Dispose of fuel properly.

9.5.2 Replacing

9.6 Fuel Tank9.6.1 General

33

– Unscrew the fuel filler cap and drain the tank.

: Use hook (1) 5910 893 8800 to pull the pickup body out of the fuel tank.

: Pull the pickup body (1) off the fuel hose and check it for contamination, replace if necessary.

Install in the reverse sequence.

34

– Unscrew the fuel filler cap and drain the tank.

– Remove the fan housing with rewind starter, b 7.2

– Remove the carburetor, b 9.2.2

– Remove the pickup body.

– Pull off the tank vent, b 9.5.2

: Pull out the fuel hoses (arrow).

Note installed position.

Install in the reverse sequence.

– Unscrew the spark plug.

– Use locking strip 4221 893 5900 to block the piston.

– Remove the blower tube and elbow, b 10.4 and b 10.6

BG 55, 65, 85 only

: Take out the screws and lift away the outer fan housing.

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932R

A16

4

: On BG 45, take out the screws and lift away the outer fan housing.

VA

932R

A16

2

9.6.2 Pickup Body

9.6.3 Fuel Hoses

Series 4140 Components BG, SH

SH 55, 85 only

: Unscrew the star nut (1), take out the screws and lift away the outer fan housing.

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932R

A16

3

1

10.1 Fanwheel

: Unscrew the nut (1) clockwise (left-hand thread).

: On SH 55, 85, remove the shredder blade (2).

: Remove the washer (3), fanwheel (4) and the washer

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932R

A16

5

32

4

1

behind it.

– Inspect all blades and replace fanwheel if necessary.

Install in the reverse sequence.

Series 4140 Components BG, SH

SH units only

– Remove suction tube, b 10.5

: Press down the retaining tab (1) on the protective screen and swing the screen open.

1

VA

932R

A16

1

: Use a screwdriver or similar tool to press down the retaining tabs (1) on the outer fan housing and lift away the protective screen (2).

: Remove the torsion spring (arrow).

Install in the reverse sequence.

: Take out the screws (1).

: Lift the right-hand side of the protective screen so that it comes out of the guide (2)

VA

932R

A16

6

2

1

– Remove the protective screen.

: Before reinstalling, check the seal (1) for damage and make sure it is properly seated.

Install in the reverse sequence.

1

VA

932R

A16

7

– Make sure the protective screen

engages in the guide.

10. Blower and Vacuum Attachment

10.2 Protective Screen (all except BG 45)

10.3 Protective Screen (BG 45 only)

35

: Insert a screwdriver or similar tool in the recess (arrow) on the blower stub and push the retaining tab up.

– At the same time, turn the blower tube counterclockwise as far as stop (1/4 turn).

– Pull the blower tube off the stub.

– Fit by inserting blower tube with lug in the stub.

– Rotate the blower tube clockwise until the bayonet coupling engages.

36

: Turn the suction tube counterclockwise as far as stop (1/4 turn).

– Pull the suction tube off the stub.

To fit, open the protective screen.

VA

932R

A09

4

: Insert suction tube so that its guide slots (arrow) engage the lugs (arrow) on the stub.

– Rotate the suction tube clockwise until the bayonet coupling engages.

: Loosen the star nut (1).

: Insert a screwdriver or similar tool in the recess (arrow) on the blower stub and push the retaining tab up.

– At the same time, turn the elbow

VA

932R

A16

8

1

counterclockwise as far as stop

(1/4 turn).

– Pull the elbow off the stub.

– Fit by inserting blower tube with lug in the stub.

: Check that rubber sealing ring (arrow) is properly seated.

– Rotate elbow clockwise until the bayonet coupling engages.

VA

932R

A16

9

10.4 Blower Tube (BG only)

10.5 Suction Tube (SH only) 10.6 Elbow (SH only)

Series 4140 Components BG, SH

11. Special Servicing Tools

No. Part Name Part No. Application Rem.

1 Locking strip 4221 893 5900 Blocking crankshaft 2 Socket 0812 540 1112 Installing and removing spline socket

head screws with electric or pneumatic screwdrivers

3 Vacuum pump 0000 850 3501 Testing crankcase and carburetor for leaks, testing tank vent

4 Carburetor and crankcase tester 1106 850 2905 Testing crankcase and carburetor for leaks

5 Nipple 0000 855 9200 Testing carburetor for leaks 6 Hose for leakage test 1110 141 8600 Testing carburetor for leaks 7 Screwdriver

Q-SW 8 x 2005910 890 2420 Carburetor nuts

8 Crimping tool 5910 890 8210 Attaching connectors to electrical wires 9 Torque wrench 5910 890 0301 0.5 to 18 Nm 1) 2)10 Torque wrench 5910 890 0311 6 to 80 Nm 1) 3)11 Socket, T 27 x 125 0812 524 2104 Installing and removing spline socket

head screws with electric or pneumatic screwdrivers, tightening with torque wrench

12 T-handle screwdriverQ - T 27 x 150

5910 890 2400 IS screws 4)

13 Hook 5910 893 8800 Removing pickup body

Remarks:

1) Always use torque wrench for tightening DG or P screws.2) Alternative: Torque wrench 5910 890 0302 with optical/acoustic signal.3) Alternative: Torque wrench 5910 890 0312 with optical/acoustic signal.4) Only use for releasing/removing DG or P screws.

37Series 4140 Components BG, SH

12. Servicing Aids

No. Part Name Part No. Application

1 Dirko gray sealant (100 g tube) 0783 830 2120 Guard on muffler

2 STIHL special lubricating oil 0781 417 1315 Bearing bore in rope rotor, rewind spring

3 Standard commercial, solvent-based degreasant containing no chlorinated or halogenated hydrocarbons

Cleaning sealing faces

38 Series 4140 Components BG, SH

39Series 4140 Components BG, SH

40 Series 4140 Components BG, SH

englisch / English0455 295 0123. M7. A5. Sä. Printed in Germany