Stihl 4137 Series User manual

STIH)
STIHL Series 4137 Components
HT 2005-04

1Series 4137 Components - HT
q
© ANDREAS STIHL AG & Co. KG, 2005
Contents
1. Introduction 2
2. Safety 3
3. Specifications 4
3.1 Fuel System 4
3.2 Tightening Torques 5
4. Troubleshooting 7
4.1 Clutch, Chain Drive,
Chain Tensioner 7
4.2 Rewind Starter 8
4.3 Fuel System 9
4.4 Engine 11
5. Engine 12
5.1 Shroud 12
5.2 Clutch 12
5.3 Clutch Drum 14
5.4 Muffler/Spark Arresting
Screen 15
5.5 Removing and Installing
the Engine 16
6. Rewind Starter 16
6.1 General 16
6.2 Removing and
Installing 17
6.3 Rope Rotor/
Rewind Spring 18
6.4 Tensioning 19
6.5 Starter Rope 20
6.6 Starter Grip 20
6.7 Carrier/Pawl 21
7. AV System 22
7.1 Repair 22
8. Throttle Control 24
8.1 Control Handle
up to 1997 24
8.1.1 Throttle Trigger /
Interlock Lever 24
8.1.2 Detent/Torsion Spring 25
8.1.3 Throttle Cable 26
8.2 Control Handle
up to 2001 27
8.2.1 Throttle Trigger/
Interlock Lever 27
8.2.2 Slide Control 28
8.2.3 Throttle Cable 28
8.3 Control Handle
from 2002 29
8.3.1 Throttle Trigger/
Interlock Lever 29
8.3.2 Contact/Detent Spring 30
8.3.3 Throttle Cable 31
8.4 Adjusting the Throttle
Cable 32
9. Fuel System 32
9.1 Air Filter 32
9.2 Carburetor 33
9.2.1 Leakage Test 33
9.2.2 Removing and
Installing 34
9.2.3 Spacer Flange 35
9.3 Servicing the
Carburetor 36
9.3.1 Flange Mounting with
Oval End Cover 36
9.3.2 Flange Mounting with
Square End Cover 37
9.3.3 Metering Diaphragm 37
9.3.4 Inlet Needle 38
9.3.5 Fixed Jet 38
9.3.6 Pump Diaphragm 39
9.4 Adjusting the
Carburetor 39
9.4.1 Carburetor with Two
Adjusting Screws 39
9.4.2 Carburetor with
LD Screw 40
9.4.3 User Adjustment,
Carburetor with
Limiter Cap 41
9.4.4 Service Adjustment,
Carburetor with
Limiter Cap 42
9.5 Tank Vent 44
9.6 Pickup Body 45
9.7 Fuel Tank/Fuel Hoses 45
10. Drive Tube 47
10.1 Drive Shaft/
Flexible Liner (HT 70) 47
10.2 Removing and
Installing Drive Tube 48
10.3 Telescopic Drive Tube
(HT 75) 49
10.3.1 Removing and
Installing 49
11. Special Servicing
Tools 54
12. Servicing Aids 55

2Series 4137 Components - HT
This service manual contains
detailed descriptions of all typical
repair and servicing procedures for
modelsHT 70andHT 75,whichare
based on the series 4137
powerhead.
If there is no specific reference to
individual machines, the procedure
is the same for all machines. There
may be minor differences in the
illustrations, depending on the
machine,butthemethodsusedand
the sequence of operations are
identical.
You will find detailed descriptions of
procedures for servicing and
repairing engine components and
CombiTools in the service manuals
for the “Series 4137 Powerhead“
and “CombiTools”.
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
supplement the service manual and
parts list until revised editions are
issued.
The special servicing tools
mentioned in the descriptions are
listed in the chapter "Special
Servicing Tools" of this manual.
Use the partnumbers 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
shown in the illustration
(above the text)
– = Action to be taken that is
not shown in the illustration
(above the text)
In the illustrations:
Pointer
Direction of movement
b4.2 Reference to another
chapter, i.e. chapter 4.2
in this example
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.
Servicing and repairs are made
considerably easier if the machine
is mounted on assembly stand (2)
5910893 3100withthe aidofclamp
(1) 5910 890 8800.
The machine can then be swivelled
to the best position for the ongoing
repair.
VA
249RA!63
2
1
Always use original STIHL
replacement parts.
They can be identified by the
STIHL part number,
the STIH) logo and the
STIHL parts symbol (
This symbol may appear alone on
small parts.
1. Introduction

3Series 4137 Components - HT
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.
Improper handling may result in
burns or other serious injuries.
Warning!
Donotbringanyfire, flame,sparkor
other source of heat near the fuel.
Allworkwithfuelmustbeperformed
outdoors only. Spilled fuel must be
wiped away immediately.
2. Safety

4Series 4137 Components - HT
3. Specifications
3.1 Fuel System Carburetor: Diaphragm carburetor
Carburetor leakage test at gauge
pressure: 80 kPa (0.8 bar)
Fuel mixture: Regular brand-name gasoline
(min. 90 RON) with STIHL 50:1
two-stroke engine oil; see instruction
manual for further details
Rated idle speed: 2,800 rpm
Rated cut-off speed: 10,500 rpm
Operation of tank vent:
- at gauge pressure: 50 kPa (0.5 bar)
- under vacuum: 20 kPa (0.2 bar)

5Series 4137 Components - HT
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
lbf.ft Nm
Screw IS-P4x16 Control handle molding (outer/inner) 0.75 1.0
Screw IS-M5x12 Control handle clamp/drive tube 3.7 5.0
Nut M5 Filter housing/carburetor/flange/screw 3.0 4.0
Screw IS-M5x16 Shroud/fan housing 2.6 3.5
Screw IS-M5x16 Shroud/starter cover/crankcase 2.6 3.5
Screw IS-M5x20 AV sleeve (clamp screw) 4.0 5.5
Screw IS-DG5x12 AV sleeve/drive tube (locking) 0.37 0.5
Screw IS-M5x20 Clamp (large)/drive tube/nut 2.2 3.0 1)
Screw IS-M5x20 Clamp (small)/drive tube/nut 2.2 3.0 1)
Screw IS-M6x25 Clamp (drive tube)/powerhead/nut 2.2 3.0 1)
M8 Clutch carrier/flywheel/crankshaft 19.2 26.0
Screw IS-M5x16 Fan housing/crankcase 5.9 8.0
M8 Carrier 10.3 14.0
Screw IS-5x16 Muffler/crankcase 7.0 9.5
Screw IS-5x16 Muffler/cylinder 8.5 11.5
Screw IS-M6x14 Clamp/drive tube/harness attachment
point 3.3 4.5
Screw IS-M5x16 Starter cover/crankcase 4.0 5.5
Screw IS-M5x25 Spacer flange/cylinder (with washer) 4.0 5.5
Screw IS-M5x25 Spacer flange/cylinder 4.0 5.5 2)
Screw IS-P5.5x12 Rope rotor/starter cover 1.8 2.5
M14x1.25 Spark plug 15.0 20.0
Remarks:
1) HT 75 only
2) with washer

6Series 4137 Components - HT
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

7Series 4137 Components - HT
4. Troubleshooting
4.1 Clutch, Chain Drive, Chain Tensioner
Condition Cause Remedy
Chain stops under load at full
throttle Clutch shoes badly worn Install new clutch shoes or a new clutch
Clutch drum badly worn Install new clutch drum
Chain rotates at idle speed Engine idle speed too high Readjust with idle speed screw
(counterclockwise)
Clutch springs stretched or fatigued Replace the clutch springs
Clutch spring hooks broken Replace the clutch springs
Loud noises Clutch springs stretched or fatigued Replace all clutch springs
Clutch shoe retainer broken Fit new retainer
Clutch shoes and retainers worn Install a new clutch
Chain sprocket wears rapidly Chain not properly tensioned Tension chain as specified
Wrong chain pitch Fit a chain of the correct pitch

8Series 4137 Components - HT
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
Rewind spring broken
(rope does not rewind) Spring overtensioned – no reserve when rope is fully extended Fit new rewind spring
Very dirty or corroded Clean or replace 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 a new pawl
Spring clip fatigued Fit new spring clip
Starter rope is difficult to pull
and rewinds very slowly Starter mechanism is very dirty (very dusty work area) 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 several times
until normal action is restored

9Series 4137 Components - HT
4.3 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 Screw home the low speed screw
slightly (see Adjusting the
Carburetor)
Setting of idle speed screw
incorrect – throttle shutter
completely closed
Set idle speed screw
correctly
Engine speed drops quickly under
load – low power Air filter dirty Clean or replace the air filter
Tank vent faulty Clean tank vent or replace if
necessary
Leak in fuel line between tank and
fuel pump Seal connections or install a new 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 a new pickup body
Fuel strainer dirty Replace the fuel strainer
Setting of high speed screw (H) too
rich Set high speed screw (H) correctly
Throttle shutter does not
open fully Check throttle control
Engine will not idle,
idle speed too high Throttle shutter opened too wide by idle speed screw (LA)Set idle speed screw (LA) correctly

10 Series 4137 Components - HT
Condition Cause Remedy
Poor acceleration Idle jet too lean Turn low speed screw (L)
counterclockwise (richer), but no
further than stop
Main jet too lean Turn high speed screw (H)
counterclockwise (richer), but no
further than stop
Inlet control lever too low
(relative to correct installed
position)
Set inlet control lever flush with top
face of carburetor body
Inlet needle sticking to valve seat Remove inlet needle, clean and
refit
Connecting bore to atmosphere
blocked Clean bore
Diaphragm gasket leaking Fit new diaphragm gasket
Metering diaphragm damaged or
shrunk Fit new metering diaphragm
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)
Set inlet control lever flush with top
face of carburetor body

11Series 4137 Components - HT
4.4 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 4137 Powerhead” service manual

12 Series 4137 Components - HT
:Remove the screw (arrow) from
the starter.
VA
936RA000
:Remove the screw (1) from the
fan housing.
:Remove the shroud (2).
Install in the reverse sequence.
VA
936RA001
12
:Make sure the gaskets on either
side of the cylinder, and the
ignition lead (arrow), are located
in the guides in the shroud.
VA
936RA304
Troubleshooting chart, b4.1.
Removing
– Remove the shroud, b5.1
:Take out the screws (arrows).
– Remove the engine from the fan
housing and put it to one side.
VA
936RA002
:Inspect the clutch drum. There
should be no scores or signs of
excessive wear.
VA
936RA003
:If there are noticeable wear
marks on the inside diameter of
theclutchdrum (1), check itswall
thickness. If it is less than about
80%of the originalthickness,fit a
new clutch drum, b5.3
VA
148RA101
80%
100%
1
!
:Pull the boot (1) off the spark
plug.
:Unscrew the spark plug (2).
VA
936RA004
1 2
5. Engine
5.1 Shroud 5.2 Clutch

13Series 4137 Components - HT
:Push the locking strip (1)
0000 893 5903 into the cylinder.
VA
366AR013
1
:Unscrew the clutch from the
crankshaft counterclockwise.
VA
936RA005
:Use hook (2) 5910 890 2800 to
remove the clutch springs (1).
VA
208RA028
21
– Pull the clutch shoes off the
carrier.
:Pull the retainers off the clutch
shoes.
VA
936RA305
– Clean all parts, b12.
– Replace any damaged parts.
Installing
VA
936RA306
Recommendation:
– If possible, always replace the
clutch as a complete assembly.
:Fit the retainers (1) on the clutch
shoes so that the narrow side (2)
is on the same side as the
number (3).
VA
208RA032
3
1 2
:Push the clutch shoes over the
arms (1) of the carrier so that the
number (2) is on the same side
as the raised hexagon (3).
VA
208RA027
2 1 3
:Clamp the clutch is a vise with
protective jaws.
VA
208RA030

14 Series 4137 Components - HT
:Attachoneendofeachspring (1)
to the clutch shoes.
:Use the hook (2) 5910 890 2800
to attach other ends of springs
and press them firmly into the
clutch shoes.
VA
936RA291
1
2
:Screw the clutch into position
(lower hexagon facing outwards)
and tighten it down firmly, b3.2
VA
936RA006
:Checkthat the plugs (arrows)are
in position in the fan housing, fit
them if necessary.
VA
936RA007
:Position the engine against the
fan housing, making sure the
lugs (1) engage the plugs (2).
– Fit fan housing mounting screws
and tighten them down firmly,
b3.2
VA
936RA008
1
2
– Removethelockingstripfromthe
cylinder.
Install all other parts in the reverse
sequence.
– Remove the rubber element (AV
system) from the fan housing,
b7.1
:Use pliers (1) 0816 610 1495 to
remove the circlip from the clutch
drum’s output stub.
VA
936RA111
1
:Use drift (1) 4180 893 4400 to
press the clutch drum out of the
ball bearing.
VA
936RA112
1
5.3 Clutch Drum

15Series 4137 Components - HT
:Check the ball bearing (arrow).
Iftheballbearingisfaulty,thewhole
fan housing has to be replaced.
VA
936RA113
:Use drift (1) 1108 893 4700 to
press home the clutch drum as
far as stop.
Install in the reverse sequence.
VA
936RA114
1
Muffler
– Remove the shroud, b5.1
:Take out the screw (arrow) at the
side of the muffler.
VA
936RA307
:Take out the inner screws
(arrows).
– Remove the muffler with gasket.
936RA308
VA
:Bend up the tab (1) on the
retainer.
:Pull out the gasket (2).
Install in the reverse sequence.
VA
936RA309
2
1
– Bend the tab down again after
fitting the gasket.
– Tighten down the muffler
mounting screws, b3.2
Install all other parts in the reverse
sequence.
Spark arresting screen
:Take out the screw (1).
:Pull out the spark arresting
screen (2).
– Clean or replace the spark
VA
936RA310
1
2
arresting screen as necessary.
Install in the reverse sequence.
5.4 Muffler/Spark Arresting
Screen

16 Series 4137 Components - HT
– Remove the shroud, b5.1
:Pull the short circuit wire
connector(arrow)offthe terminal
on the ignition module.
VA
935RA076
:On machines with two short
circuit wires, pull the connectors
(arrows) off the terminals on the
ignition module.
VA
935RA077
:On machines with one short
circuit wire, remove throttle cable
lug from lower screw (arrow).
936RA430
VA
:Disconnect the throttle cable’s
nipple (1) from the slotted pin (2)
on the carburetor’s throttle lever.
VA
366RA007
1
2
:Take the throttle cable out of the
tensioner.
VA
936RA229
:Take out the screws (arrows).
– Remove the engine from the fan
housing.
Install in the reverse sequence.
VA
936RA002
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
outsidetemperaturesthelubricating
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
therewindspring,must be removed
and disassembled. Take particular
care when removing the spring.
Clean all parts, b12.
Lubricate the rewind spring and
starter post with STIHL special
lubricant, see b12, before
installing.
5.5 Removing and Installing
the Engine 6. Rewind Starter 6.1 General

17Series 4137 Components - HT
– Remove the shroud, b5.1
:On machines with a guard, take
out the M5x30 screws (arrows).
– Remove the guard (1).
VA
936RA375
1
:Takeoutthe screws (arrows) – or
only the upper screw on
machines with a guard.
VA
366RA116
:On machines with one short
circuit wire, remove throttle cable
lug from lower screw (arrow).
– Remove the rewind starter.
Install in the reverse sequence.
936RA430
VA
:Check that the plug (arrow) in the
rewind starter is correctly seated.
Replace if damaged.
VA
936RA037
:Fit the rewind starter so that the
lug (1) engages the plug (2).
VA
936RA038
1
2
:On machines with one short
circuit wire, secure the throttle
cable lug with the lower screw
(arrow).
Install all other parts in the reverse
sequence.
936RA430
VA
6.2 Removing and Installing

18 Series 4137 Components - HT
A replacement rope rotor comes
with a new rewind spring.
– Remove the rewind starter,
b6.2
Relieving tension of rewind
spring
There will be no tension if either the
starter rope or rewind spring is
broken.
– Pull out the starter rope about
30 cm (12“) and hold the rope
rotor steady.
:Engage the rope in the notch
(arrow) in the rotor and make a
loop.
936RA431
VA
:Use the loop to rotate the rotor
clockwise until the spring is no
longer under tension.
936RA432
VA
:Take out the screw (arrow).
VA
936RA058
:Carefully pull the rope rotor off
the starter post.
:Carefully pull the rope rotor off
the starter post.
The rewind spring is installed in the
rope rotor. The spring may pop out
VA
936RA040
and uncoil if the rope rotor is not
removed very carefully.
Always wear safety glasses
– Remove the pieces of broken
spring from the rewind starter.
– Toreplacetheroperotor, remove
the starter rope, b6.5
Install in the reverse sequence.
Pay attention to correct installed
position of the rewind spring.
The rewind spring may pop out of
the rope rotor and uncoil if it is not
installed very carefully. Use the
following procedure to fit the rewind
spring:
:Engage the outer spring loop in
the recess (arrow) and fit the
rewind spring counterclockwise,
starting outside and working
inwards.
936RA042
VA
:Check the distance of the inner
spring loop from the bore and
correct if necessary. Dimension
"a" must be 2 mm.
VA
936RA043
a
6.3 Rope Rotor/Rewind
Spring

19Series 4137 Components - HT
– Lubricate the bore with STIHL
special lubricant, b12.
– Fit the rotor on the starter post so
that the lug on the rotor engages
the inner spring loop.
Turn the rope rotor a little and let it
go – it must spring back.
:Insert the screw (arrow) and
tighten it down firmly, b3.2
– Tension the rewind spring, b6.4
Install all other parts in the reverse
sequence.
VA
936RA058
:Make a loop in the starter rope.
– Engage the starter rope in the
notch in the rotor.
VA
936RA045
:Grip the rope close to the rotor
and use it to turn the rotor about
six full turns counterclockwise.
VA
936RA046
:Hold the rope rotor steady.
:Pull out the rope with the starter
grip and straighten it out.
VA
936RA047
– Holdthestartergripfirmlytokeep
the rope tensioned.
– Let go of the rope rotor and
slowly release the starter rope so
that it can rewind properly.
The rewind spring is correctly
tensioned when the starter grip sits
firmly in the rope guide bushing
without drooping to one side. If this
is not the case, tension the spring
by one additional turn.
When the starter rope is fully
936RA433
VA
extended, it must still be possible to
rotate theroperotorat 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.
– Install the rewind starter, b6.2
6.4 Tensioning