STIHL MS 780, 880
STIH)
STIHL MS 780, 880
2009-08
Contents
1.
Introduction
3
2.
Safety Precautions
5
8.
Engine
8.1
Muffler with Spring Clip/
Spark Arresting
Screen
30
Screw Mounted Muffler /
Spark Arresting
Screen
32
Leakage Test
34
Preparations
34
Vacuum Test
36
Pressure Test
36
Oil Seals
37
Carburetor Box Cover 38
Removing and Installing
the Shroud
39
Cylinder
40
Crankshaft
43
Removing and
Installing
43
Bearings / Crankcase 48
Piston
50
Removal
50
Installing
51
Piston Rings
52
Decompression Valve 53
8.2
3.
Specifications
6
3.1
3.2
3.3
3.4
3.5
Engine
Fuel System
Ignition System
Chain Lubrication
Tightening Torquese
6
6
6
6
7
4.
Troubleshooting
9
4.1
4.2
4.3
4.4
4.5
4.6
4.7
5.
Clutch
9
Chain Drive, Chain Brake,
Chain Tensioner
10
Chain Lubrication
11
Rewind Starter
12
Ignition System
13
Carburetor
15
Engine
18
Saw Chain /
Guide Bar
8.3
8.3.1
8.3.2
8.3.3
8.4
8.5
8.6
8.7
8.8
8.8.1
8.8.2
8.9
8.9.1
8.9.2
8.10
8.11
30
10.
Rewind Starter
73
10.1
10.2
General
– Removing and
Installing
Pawls
Rope Rotor
Starter Rope / Grip
Tensioning the Rewind
Spring
Replacing the Rewind
Spring
73
10.3
10.4
10.5
10.6
10.7
11.
11.1
11.8
Annular Buffer on Oil
Tank at Clutch Side
Annular Buffer on Oil
Tank at Ignition Side
Annular Buffer at
Clutch Side
Annular Buffer at
Ignition Side
Stop Buffer at
Ignition Side
Stop Buffer on Ignition
Module
Stop Buffer at
Clutch Side
Handlebar
12.
Control Levers
11.2
11.3
11.4
11.5
11.6
19
9.
Ignition System
54
11.7
5.1
6.
Spiked Bumper / Chain
Catcher
19
Clutch
9.1
9.2
9.2.1
20
9.2.2
6.1
Clutch Drum
22
7.
Chain Brake
23
7.1
7.2
Checking Operation
23
Removing and Installing
the Brake Band
23
Brake Lever
25
Cam Lever
26
Pins
27
Chain Tensioner
28
Bar Mounting Studs
29
9.3
9.4
7.3
7.4
7.5
7.6
7.7
9.5
9.6
9.6.1
9.6.2
9.6.3
RA_550_00_01_02
9.6.4
9.6.5
9.7
Ignition Timing
54
Ignition Module
54
Removing and Installing
– Version with two
mounting screws
54
Removing and Installing
– Version with three
mounting screws
56
Testing the Ignition
Module
59
Spark Plug Boot /
Ignition Lead
60
Flywheel
61
Short Circuit Wire
63
Testing
63
Removing and Installing
– Version with three
mounting screws
63
Removing and Installing
– Version with cable
channel
66
Ground Wire
68
Contact Spring
69
Ignition System
Troubleshooting
70
Servicing the
AV System
73
74
74
75
77
77
79
79
80
80
81
81
82
82
83
84
12.1
Switch Shaft
12.1.1 Removing and
Installing
12.1.2 Throttle Trigger/
Interlock Lever
12.1.3 Choke and Throttle
Rods with Levers
87
13.
90
Chain Lubrication
84
84
86
13.1
13.2
13.3
Pickup Body
90
Oil Suction Hose
90
Removing and Installing
the Oil Pump
91
13.3.1 Spur Gear – Removing
and Installing
92
13.4
Valve
93
q
© ANDREAS STIHL AG & Co. KG, 2009
MS 780, MS 880
1
Contents
14.
Fuel System
14.1
14.2
Air Filter
94
Removing and Installing
the Filter Base
94
Carburetor
– Removing and
Installing
94
Leakage test
97
Servicing the Carburetor
Tillotson Carburetor
97
Metering Diaphragm 97
Inlet Needle
98
Fixed Jet
99
Pump Diaphragm
99
Choke Shaft /
Choke Shutter
100
Throttle Shaft /
Throttle Shutter
102
Adjusting Screws
103
Servicing the Carburetor
– Walbro Carburetor 105
Metering Diaphragm 105
Inlet Needle
106
Fixed Jet
107
Pump Diaphragm
107
Choke Shaft /
Choke Shutter
108
Throttle Shaft /
Throttle Shutter
110
Adjusting Screws
111
Adjusting the
Carburetor
113
Basic Setting
113
Standard setting
114
Intake Manifold
– Removing and
Installing
115
Impulse Hose
116
Tank Vent
117
Testing
117
Removing and
Installing
118
Fuel Intake
118
Pickup Body
118
Fuel Hose
118
Tank Housing
– Removing and
Installing
119
14.3
14.4
14.5
14.5.1
14.5.2
14.5.3
14.5.4
14.5.5
14.5.6
14.5.7
14.6
14.6.1
14.6.2
14.6.3
14.6.4
14.6.5
14.6.6
14.6.7
14.7
14.7.1
14.7.2
14.7.3
14.7.4
14.8
14.8.1
14.8.2
14.9
14.9.1
14.9.2
14.9.3
15.
16.
2
94
Special Servicing
Tools
121
Servicing Aids
123
MS 780, MS 880
Introduction
This service manual contains
detailed descriptions of all the repair
and servicing procedures specific 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.
The special tools mentioned in the
descriptions are listed in the chapter
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.
Symbols are included in the text and
pictures for greater clarity.
The meanings are as follows:
In the descriptions:
A fault on the machine may have
several causes. To help locate the
fault, consult the chapter on
"Troubleshooting" 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.
: = 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:
A Pointer
aDirection of movement
1
3
2
219RA000 TG
1.
Servicing and repairs are made
considerably easier if the machine
is mounted to assembly stand (3)
5910 890 3100. To do this, secure
the mounting plate (2)
5910 850 1650 to the assembly
stand with two screws (1) and
washers.
The screws must not project since
they, depending on the machine,
may damage housings when the
machine is clamped in position.
The above operation is not
necessary with the new assembly
stand 5910 890 3101 since the
mounting plate is already fitted.
@ 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.
MS 780, MS 880
3
216RA000 TG
Engage the bar mounting studs in
the outer bores in the mounting
plate and secure the saw in position
with the nuts (arrows).
Preparations for servicing
Remove the chain sprocket cover,
saw chain and guide bar before
carrying out repairs or mounting the
machine to the assembly stand.
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.
4
MS 780, MS 880
2.
Safety Precautions
If the power tool is started up in the
course of repairs or maintenance
work, observe all local and countryspecific 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.
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.
MS 780, MS 880
Fuel system – hose barb
connectors
Pull off or push on fuel hoses in line
with the connector, preferably by
hand, to ensure the tightness of the
fuel system.
Avoid damaging the hose barb
– do not use sharp-edged pliers,
screwdrivers, etc.
Do not cut open fuel hoses with a
knife or similar tool.
Do not re-use fuel hoses after
removal. Always install new hoses
– fuel hoses may be overstretched
during removal.
Install new fuel hoses either dry or
with the aid of STIHL press fluid,
b 16.
Other press fluids are not approved
and may result in damage to the fuel
hoses.
Coat the ends of the hoses and the
connectors with STIHL press fluid
and then push the new hoses on to
the hose barbs, b 16.
5
3.
Specifications
3.1
Engine
Displacement:
Bore:
Stroke:
Engine power to ISO 7293:
Maximum permissible engine speed
with bar and chain:
Idle speed:
Clutch:
Clutch engages at:
Crankcase leakage test
at gauge pressure:
under vacuum:
3.2
3.3
3.4
MS 780
MS 880
121.6 cm3
60 mm
43 mm
5.6 kW (7.8 bhp)
at 8,000 rpm
121.6 cm3
60 mm
43 mm
6.4 kW (8.7 bhp)
at 8,500 rpm
11,000 rpm
2,700 rpm
Centrifugal, without linings
3,400 rpm
11,000 rpm
2,700 rpm
Centrifugal, without linings
3,400 rpm
0.5 bar
0.5 bar
0.5 bar
0.5 bar
Fuel System
Carburetor leakage test at
gauge pressure:
Operation of tank vent at
gauge pressure:
Fuel:
0.5 bar
as in instruction manual
Air gap between ignition
module and fanwheel:
Spark plug (suppressed):
Electrode gap:
0.20...0.30 mm
NGK BPMR 7 A
0.5 mm
0.8 bar
Ignition System
Chain Lubrication
Speed-controlled oil pump with reciprocating piston and
manual flow control
Oil delivery rate:
Adjustable oil pump
Ematic position
Special accessory
Oil delivery rate:
Oil pump with increased
delivery rate:
(oil delivery rate is not
adjustable)
6
at 10,000 rpm
14.0...36.0 (+/- 5.0) cm3/min
21.0 (+/- 3.0) cm3/min
at 10,000 rpm
50.0 (+/- 5.0) cm3/min
MS 780, MS 880
3.5
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
Nm
Screw
Screw
Screw
Screw
Screw
M 4x8
B 3.9x13
M 4x12
M 4x12
M 6x30
3.5
2.0
4.0
3.0
12.0
Screw
Screw
Screw
Screw
Nut
Nut
Screw
Screw
Screw
Nut
M 10x27
M 4x12
M 4x12
M 4x12
M 10x1
M5
M5
P 6x32.5
P 6x21.5
M 5x35
M6
Screw
Nut
Nut
Nut
Screw
Screw
Screw
Screw
M 5x20
M5
M5
M6
M 6x16
M 6x18
M 6x16
M 6x18
Screw
Screw
Screw
Screw
Carrier
Screw
Screw
M 5x25
M 5x28
P 4x19
M 5x20
M 14x1 L
M 4x12
M 4x12
Chain tensioner cover plate/crankcase
Cover plate/chain sprocket cover
Exhaust cover/muffler
Brake band/crankcase
Collar stud/crankcase, for muffler (MS 780/
new MS 880)
Collar stud / crankcase, for bar
Cover, chain brake/crankcase
Cover, oil pump/crankcase
Cover, spur gear/crankcase
Decompression valve
Filter cover, twist lock
Flange/carburetor/tank housing
Handlebar, right, stiffener/tank housing
Handlebar, bottom/tank housing
Hand guard/fan housing/crankcase
Helper's handle/front handle/screw
(2-man saw)
Shroud/crankcase
Shroud/cylinder
Chain catcher/spiked bumper/crankcase
Spiked bumper/chain sprocket cover
Spiked bumper/crankcase, top/locknut
Spiked bumper/crankcase, top/locknut
Spiked bumper/crankcase, bottom
Spiked bumper/crankcase, bottom
(Z version)
Crankcase (old MS 880)
Crankcase (MS 780/new MS 880)
Bearing, switch shaft/tank housing
Fan housing/crankcase
Carrier / crankshaft
Oil oump/crankcase, front top
Oil pump/crankcase, front bottom and rear
MS 780, MS 880
Remarks
4)
1), 4)
1)
30.0
3.5
3.5
3.0
14.0
1.0
5.0
8.0
8.0
7.0
6.0
1)
4)
4)
4)
7.0
3.5
6.0
7.5
7.5
7.5
7.5
7.5
4)
11.5
10.0
1.0
7.0
80.0
3.5
3.5
2)
2)
4)
4)
4)
1), 4
1), 4)
4)
4)
4)
6)
4), 7)
4)
7
Fastener
Thread size
For component
Torque
Nm
Remarks
Screw
Screw
Screw
Screw
Screw
M 6x40
P 6x19
M 5x12
M 4x12
M5
7.0
5.5
9.0
4.0
10.0
1), 4)
Screw
Screw
Crankshaft
Screw
Screw
Screw
Stud
Screw
Screw
Screw
Spark plug
Screw
Screw
Screw
M 5x16
M 5x6
M 10x1
M 4x12
M 4x8
M 3x20
M 5x8.5
M 5x16
M 5x16
P 4x19
M 14x1.25
M 5x25
M 5x20
M 6x30
Annular buffer, left top/retainer/tank housing
Annular buffer, bottom/tank housing
Annular buffer plate, left top/crankcase
Rewind spring, fan housing
Muffler/collar stud with spring washer (MS
780/new MS 880)
Muffler/cylinder (MS 780/new MS 880)
Muffler casing, top (MS 780/new MS 880)
Flywheel/crankshaft
Segment/fan housing
Side plate/crankcase
Clamp/manifold (MS 780/new MS 880)
Stud/cylinder
Support/crankcase (old MS 880)
Support/muffler (old MS 880)
Tank housing/handle molding
Spark plug
Ignition module/crankcase (old MS 880)
Ignition module/crankcase
Cylinder/crankcase
10.0
6.5
45.0
2.0
3.0
0.5
3.5
10.0
10.0
1.0
25.0
9.0
8.0
15.0
1), 4)
4)
1), 4), 5)
1), 4)
6)
4)
4)
3)
4)
4)
1), 4)
5)
4)
Remarks:
1) Loctite 242 or 243, medium strength
2) Loctite 649, high strength
3) Loctite 270, high strength
4) Screws with binding head
5) Micro-encapsulated screws
6) Degrease joint and mount oil-free
7) Use Hylomar HYL sealant
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.
8
MS 780, MS 880
4.
Troubleshooting
4.1
Clutch
Condition
Cause
Remedy
Saw chain stops under load at full
throttle
Clutch shoes badly worn
Install new clutch
Clutch drum badly worn
Install new clutch drum
Engine idle speed too high
Check carburetor settings and
readjust properly if necessary
Saw chain rotates at idle speed
Clutch springs stretched or fatigued Replace the clutch springs or install
new clutch
Clutch spring hooks broken
Loud noises
MS 780, MS 880
Replace the clutch springs
Clutch springs stretched or fatigued Replace all clutch springs
Needle cage damaged
Fit new needle cage
Clutch shoe retainer broken
Install new retainer or clutch
Clutch shoes and carrier worn
Install new clutch
9
4.2
Chain Drive, Chain Brake, Chain Tensioner
Condition
Cause
Remedy
Chain sprocket wears rapidly
Chain not properly tensioned
Tension chain as specified
Wrong chain pitch
Fit chain of correct pitch
Insufficient chain lubrication
Check chain lubrication
Chain sprocket worn
Fit new chain sprocket
Clutch shoes badly worn
Install new clutch
Clutch drum badly worn
Install new clutch drum
Brake band does not release fully
or sticks
Check freedom of movement and
operation of brake band
Brake spring stretched or broken
Fit new brake spring
Brake band stretched or worn
Fit new brake band
Clutch drum worn
Install new clutch drum
Saw chain stops under load at full
throttle
Saw chain does not stop
immediately when brake is
activated
10
MS 780, MS 880
4.3
Chain Lubrication
In the event of trouble with the chain lubrication system, check and rectify other sources of faults before
disassembling the oil pump.
Condition
Cause
Remedy
Chain receives no oil
Oil tank empty
Fill up with oil and check setting of
oil pump if necessary
Oil inlet hole in guide bar is blocked Clean oil inlet hole
Machine losing chain oil
Oil pump delivers insufficient oil
MS 780, MS 880
Intake hose or pickup body clogged
or intake hose ruptured
Fit new intake hose and pickup
body
Valve in oil tank blocked
Clean or replace valve
Spur gear broken
Fit new spur gears
Oil pump damaged or worn
Install new oil pump
Oil pump body damaged
Install new oil pump
Oil pump damaged or worn
Install new oil pump
Oil intake hose connection leaking
or damaged
Install new oil intake hose
Sealing ring on oil pump outlet
damaged or missing
Replace the sealing ring
Oil pump worn
Install new oil pump
Oil pump delivery rate set too low
Adjust oil pump
(only on version with adjustable oil
pump)
Pickup body in oil tank clogged
Clean the pickup body or replace if
necessary.
11
4.4
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 very dirty or
corroded
Clean or replace rewind spring
Insufficient spring tension
Check rewind spring and increase
tension
Rewind spring broken
Fit new rewind spring
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
Spring clip installed wrong
Install spring clip correctly
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 small
amount of standard solvent-based
degreasant (containing no
chlorinated or halogenated
hydrocarbons), then pull rope
carefully several times until normal
action is restored
Decompression valve is not open
Open, check and replace
decompression valve if necessary
Starter rope does not rewind
Starter rope is difficult to pull or
rewinds very slowly
12
MS 780, MS 880
4.5
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
MS 780, MS 880
Ignition lead loose in ignition
module
Secure ignition lead properly
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
damaged or pole shoes have
turned blue
Install new flywheel
Ignition timing wrong, flywheel out
of adjustment, key in flywheel has
sheared off
Fit key if necessary and secure
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
13
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 and replace if
necessary
Ignition module faulty
Install new ignition module
14
MS 780, MS 880
4.6
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
Metered diaphragm deformed
Fit a new metering diaphragm
Air filter dirty
Clean air filter or replace if
necessary
Poor acceleration
Setting of low speed screw too lean Check basic carburetor setting,
correct if necessary
MS 780, MS 880
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
Impulse hose damaged or kinked
Install new impulse hose
Tank vent faulty
Replace tank vent
Leak on fuel hose from tank to
carburetor
Seal connections or install new fuel
hose
15
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
Idle jet bores
or ports blocked
Clean the carburetor
Low speed screw 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
Tank vent faulty
Replace tank vent
Leak on fuel hose from tank to
carburetor
Seal connections or install new fuel
hose
Engine idle speed too high
Reset low speed screw L correctly
Clutch does not release even
though idle speed is correct
Check the clutch
Engine stalls at idle speed
Saw chain rotates at idle speed
16
MS 780, MS 880
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 rod
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 on fuel hose from tank to
carburetor
Seal connections or install new fuel
hose
Setting of high speed screw H too
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
Impulse hose damaged or kinked
Install new impulse hose
Ignition timing wrong, flywheel out
of adjustment, key in flywheel has
sheared off
Fit key if necessary and secure
flywheel properly or install new
flywheel
MS 780, MS 880
17
4.7
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
Piston rings worn or broken
Fit new piston rings
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/impulse hose severely kinked
or damaged
Fit new hoses or position them free
from kinks
Decompression valve is not closed
Close, check and replace
decompression valve if necessary
Insufficient cylinder cooling. Air
inlets in fan housing blocked or
cooling fins on cylinder very dirty
Thoroughly clean all cooling air
openings and the cylinder fins
Engine does not deliver full power
or runs erratically
Engine overheating
18
MS 780, MS 880
Saw Chain / Guide Bar
3
1
3
3
1
2
216RA002 TG
2
165RA002 TG
1
1
2
216RA425 TG
5.
Wear work gloves
to protect your hands from injury.
: Hold the guide lug (1) steady and
unscrew the nut (2).
: Hold the nut (arrow) steady and
take out the screws (1).
: Unscrew the hex nuts (1).
: Unscrew the nuts (arrows).
– Remove the deflector (2) and
spiked bumper (3).
: Remove the chain sprocket
cover (2).
– Remove the spiked bumper (3).
Always use new self-locking nuts.
Always use new self-locking nuts.
: Remove the guide bar (3) with
chain.
– Reassemble in the reverse
sequence.
– Reassemble in the reverse
sequence.
– Tightening torques, b 3.5
– Reassemble in the reverse
sequence.
Spiked Bumper on Crankcase
5.1
Spiked Bumper / Chain
Catcher
2
– Remove the chain sprocket
cover, b 5
1
216RA023 TG
Chain Catcher / Spiked Bumper
on Chain Sprocket Cover
: Take out the screw (1).
: Remove the inner side plate (2).
216RA001 TG
1
: Remove the E-clip (arrow).
– Pull off the roller (1).
MS 780, MS 880
19
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