Technical Information · issue 25 of 2010
New chain saws STIHL MS 271, MS 291
IssueTI 25/2010
Engine family 1141
Part changes (2)
| Was | Becomes | What the bulletin says |
|---|---|---|
| 5910 855 4201 | 5910 890 4504 | Item Designation Part number Use 1 Press sleeve 1141 893 2401 Press in oil seal 2 Flange 5910 855 4201 Engine leakage test Puller 5910 890 4504 The previous puller 1135 890 4500 is being replaced by the new version 5910 890 4504. |
| 4224 893 2501 | 5910 855 4201 | Rework information The previous flange 4224 893 2501 is being replaced by the new version 5910 855 4201. |
Full text
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STIH)
Technical Information 25.2010
New chain saws STIHL MS 271, MS 291 – Series 1141
Contents
1. Technical description
2. Specifications
3. Special tools and service accessories
4. Service notes
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)m~ge 2 Technical Information 25.2010
The new 1141 series STIHL MS 271 and STIHL 1. Technical description
MS 291 chain saws with an innovative engine
concept and filter system are especially powerful, 1.1 Reduced emissions engine
economical, clean and low-maintenance. These
In the new 1141 series chain saws, the reduced
new chain saws are designed for use by farmers,
emissions engine technology is implemented
landscapers and tradespeople. Their applications
without an additional clean air port, without an air
range from cutting firewood and maintaining forest
shutter and without a dual manifold.
stands to wood work in skilled trades.
Characteristic features of the MS 271 and MS 291 Functional principle
chain saws:
- modern, low-emission engine with reduced fuel
consumption
- high torque over a wide range of speeds and
simultaneously fast-revving for use in limbing
- air filter with pre-separator for substantially
longer air filter service life
- outstanding control and rigidity with a low level
of vibration
Also available:
- MS 291 C-BEQ with quick chain tensioner,
Easy2Start™, manual fuel pump and STIHL
Quickstop® Plus chain braking system.
1
5902TI003 KN
A baffle plate (1) located in the carburetor between
the choke and throttle shutters separates the fresh
fuel mix and clean air paths from one another.
The installation space required for the carburetor
and intake elbow is nearly the same as that for
a conventional two-stroke engine without stratified
scavenging.
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Technical Information 25.2010 Page 3
1.2 Air filter system with pre-separator
2710TI002 KN
- HD2 filter – black filter frame, pleated filter fabric
The material of the HD2 filter stands out because of
its oil and water repellent characteristics. The filter
characteristics are preserved even after numerous
cleaning cycles. The large surface area of the HD2
0001TI002 KN
filter is attained by folding (pleating) the material.
Operating conditions:
The intake air is swirled and diverted horizontally by For extreme winter conditions (e.g., powdered or
the ramp in front of the ignition module. The larger drifting snow) or very dusty operating environments
and heavier particles carried in the air (black arrows)
are expelled upward and outward. 1.2.3 Removing, cleaning and installing the air
Via the pre-separator duct, the pre-cleaned air (gray filter
arrows) is fed to the air filter. The air filter is secured with a bayonet-type lock and
The air filter system can be adapted to different can be detached from the filter base without tools.
operating conditions by the insertion of different air
filters. Retrofitting is simple.
1.2.1 Fleece filter
For normal and dry applications.
1.2.2 HD2 filter
The newly developed HD2 professional fine particle
air filter incorporated in the MS 261 can also be
used in the MS 271 and the MS 291.
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)m~ge 4 Technical Information 25.2010
Removing the air filter Installing the air filter
. Remove the shroud and clean away loose dirt
from around the filter
1
2
1
2710TI004 KN
2
2710TI003 KN
. Fit air filter
. Press the air filter in the direction of the filter
. Turn air filter 1/4 turn counterclockwise and housing and simultaneously turn it clockwise
remove in the direction of the rear handle until the air filter engages – when installed in the
correct position, the "STIHL" logo must be
Damaged filters must always be replaced.
horizontal
Cleaning the air filter
. Refit the shroud
. Lightly knock out the air filter to remove the
particles 1.3 Anti-vibration system
In case of stubborn dirt or stuck filter fabric:
. Wash the filter in STIHL special-purpose
2
cleaner (special accessory) or a clean, non-
flammable cleaning liquid (e. g., warm soapy
water) – rinse the filter from inside to out under 3
a water jet – do not use high-pressure cleaners 6
Dry all filter parts – do not expose to extreme heat.
Do not use compressed air.
5902TI009 KN
6 6 5 4 1
The new antivibration system consists of spring (1),
springs (2) and (3) with integral overload protection,
the Cellasto AV element (4), the Cellasto stop
buffer (5) and the stop buffers (6).
. The combination of these elements leads to
a very low level of vibration.
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Technical Information 25.2010 Page 5
1.4 Shroud Function
In this activation system the clutch drum is clamped
by the hand brake, stopping movement of the chain,
when the right hand is completely removed from the
throttle trigger and the trigger lockout is released.
The trigger lockout acts as the activating
mechanism for this mode of chain brake
engagement.
The brake band releases the clutch drum when the
trigger lockout is pressed down again, allowing the
chain to move.
This means the chain brake on chain saws
equipped with the Quickstop® Plus activation
system can be activated in three different ways:
- Manually, either by the operator intentionally
tripping the front hand guard by pushing it
forward or by the front hand guard tripping as
a result of contact with the operator´s hand
during a rotational kickback reaction. This mode
of activation is designed to stop the movement
2710TI005 KN
of the chain in fractions of a second after
activation occurs.
- Inertially, by movement of the front hand guard
The one-piece shroud is fastened with three screws. in reaction to the rotation of the chain saw. This
This provides fast and easy access to the air filter mode of activation also is designed to stop
and cylinder. movement of the chain in fractions of a second
after activation occurs. Note: activation requires
generation of sufficient inertial energy during the
kickback reaction.
1.5 STIHL Quickstop® Plus chain brake
system (MS 291 C-BEQ) - Manually, by release of the throttle trigger and
trigger lockout. This rear-handle activation of the
The STIHL Quickstop® Plus chain brake system is
chain brake results in slower braking times – up
a unique convenience feature when:
to a second or longer after activation depending
- Carrying a chain saw on the condition of the chain brake and
- Handling a chain saw during short interruptions activation system.
in cutting Warning: This mode of activation of the chain brake
is not designed to reduce the risks of injury from
kickback. Rather, the trigger lockout activation
mode for the chain brake primarily serves as
a convenience item for the operator.
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)m~ge 6 Technical Information 25.2010
2. Specifications 2.4 Fuel system
Carburetor
2.1 Engine All-position diaphragm carburetor
STIHL single cylinder two-stroke engine
MS 271 MS 291 Standard setting with limiter cap on the high
speed screw
Displacement: 3.06 cu in 3.39 cu in Low speed screw L: 1 turn open
(50.2 cm3) (55.5 cm3)
Bore: 1.76 in. 1.85 in. High speed screw H: 3/4 turn open
(44.7 mm) (47.0 mm) (max. to stop)
Piston stroke 1.26 in. 1.26 in.
(32.0 mm) (32.0 mm)
Power output 3.49 hp 3.85 hp
Basic setting without limiter cap on the high
according to (2.6 kW) at (2.8 kW) at
speed screw (in service)
ISO 7293: 9,500 rpm 9,500 rpm
Idle speed: 2,800 rpm 2,800 rpm Low speed screw L: 1 turn open
High speed setting
when performing High speed screw H: 1 1/2 turns open
repairs with guide
bar and saw chain: 13,000 rpm 13,000 rpm Fuel mixture
See Instruction Manual
Fuel tank capacity: 16.9 fl.oz (500 cc)
2.2 Weight
dry, without bar and chain
MS 271: 12.3 lbs.
(5.6 kg) 2.5 Chain lubrication
MS 291: 12.3 lbs.
(5.6 kg) Oil pump: Speed-controlled oil
pump – additional
MS 291 C-BEQ: 13.9 lbs.
manual oil flow control
(6.3 kg)
Oil tank capacity: 8.1 fl.oz (240 cc)
2.3 Ignition system
Ignition module: Electronically controlled
with adjustment of the
ignition timing
Spark plug NGK BPMR 7 A
(suppressed): Bosch WSR 6 F
Electrode gap: 0.020 in. (0.5 mm)
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Technical Information 25.2010 Page 7
2.6 Cutting attachment
2.6.1 MS 271, MS 291
STIHL reduced kickback guide bars
(with green label)
STIHL ROLLOMATIC® E and
STIHL ROLLOMATIC® ES (.325")
Bar lengths 16, 18, 20 in.
(pitch .325"): (40, 45, 50 cm)
Sprocket nose: 11 tooth
Groove width: 0.063 in. (1.6 mm)
STIHL reduced kickback saw chain
(with green label)
RAPID™ Micro Comfort 3 (RMC3)
Pitch: 0.325" (8.25 mm)
Drive link gauge: 0.063 in. (1.6 mm)
Chain sprocket
7-tooth for .325"
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)m~ge 8 Technical Information 25.2010
3. Special tools and service
accessories
3.1 Special tools
The following new special tools are required
2
2710TI006 KN
Item Designation Part number Use
1 Press sleeve 1141 893 2401 Press in oil seal
2 Flange 5910 855 4201 Engine leakage test
Puller 5910 890 4504
The previous puller 1135 890 4500 is being
replaced by the new version 5910 890 4504.
The new puller is characterized by a clamping
bridge extended from 10 mm to 60 mm with oblong
holes for the fastening screws.
In versions with Easy2Start™, the new puller with
the extended clamping bridge is required in order to
remove the flywheel. Puller 1135 890 4500 can
continue to be used with the standard versions.
In the future, only the new puller 5910 890 4504 will
be available from the factory.
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Technical Information 25.2010 Page 9
Rework information
The previous flange 4224 893 2501 is being
replaced by the new version 5910 855 4201.
An existing flange 4224 893 2501 in which the hole
is missing can be reworked in accordance with the
following drawing.
39,25 mm
2710TI007 KN
3.2 Service accessories
Designation Part number Use
Set of carburetor parts 1141 007 1006 Carburetor repairs
Grease (225 g tube) 0781 120 1111 Oil seals, oil pump drive, sprocket bearings, chain tensioner
Bearing and sliding surfaces for throttle trigger, brake lever
and trigger lockout
Tube of sealant Dirko 0783 830 2000 Seal between engine pan and cylinder
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)m~ge 10 Technical Information 25.2010
4. Service notes
The specific national safety regulations and the 1
safety instructions in the Instruction Manual must be
observed when starting and operating the chain
saw.
Only use the chain saw with the shroud mounted –
otherwise the rotating fan wheel poses a risk of
injury and there is a risk of engine damage due to
overheating.
5902TI015 KN
4.1 Carburetor
With this carburetor, the high speed screw H can . Set master control lever to position STOP 0
only be adjusted by the user within a range of an
. Insert screwdriver in the opening (arrow) and
approx. 3/4 turn.
pry out the switch shaft (1)
4.1.1 New limiter caps . Remove the short circuit wire
To comply with various national and international
exhaust laws and regulations, a new generation of
limiter caps is used in the MS 271 and MS 291 as
well as the MS 261. These limiter caps are
characterized by a zinc body and a plastic inner part
as a connecting piece with the adjusting screw.
3
The new puller has an M3 lefthanded thread for
removing the limiter cap.
5902TI016 KN
4.1.2 Removing the carburetor 4
. Remove shroud and air filter 1
. Set master control lever to choke shutter
. Unscrew nuts (1) and remove baffle (2)
closed l
. Tilt the filter base (3) toward the rear off of the
stud bolts
. Release the filter base from the buffer (5) and
then swing it away to the left – buffer (4) will
1 release automatically
. Remove carburetor
During the operation, the filter base will hang from
the short circuit and ground wire on the side of the
machine.
5902TI014 KN
. Block the choke lever at the carburetor and
move the master control lever toward Stop 0 –
rod (1) will jump out of the mount
4.1.3 Removing the limiter cap
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Technical Information 25.2010 Page 11
4.1.4 Basic setting
After servicing or replacement of the adjusting
3 screws, it is necessary to perform a basic setting of
2 the carburetor.
1
. Check the air filter – clean or replace it if
necessary
. Check the spark arresting screen in the muffler
– clean or replace it if necessary
5902TI017 KN
The following screwdrivers should be used for the
basic setting.
- Low speed screw L
. Screw the puller (1) 5910 890 4502 (special Flat head screwdriver 5910 890 2305
tool) counterclockwise (left-hand thread) about
five turns into the limiter cap
- High speed screw H
. Remove the limiter cap (2)
Screwdriver 5910 890 2306 with hex blade
. Use the screwdriver (5910 890 2306) to SW 2
unscrew the high speed screw (3) with the
plastic segment . Carry out basic setting of the adjusting screws –
set adjusting screw by turning counterclockwise
starting with the screws lightly seated
Low speed screw L: 1 turn open
High speed screw H: 1 1/2 turns open
Fitting the limiter cap on the high speed screw
5902TI018 KN
. If the high speed screw (H) is going to be
reused, remove the plastic insert
Used caps must not be refitted, as they are
damaged when pulled off!
1
Service work on metering diaphragm, pump
diaphragm, inlet needle, lever, gaskets, choke
5902TI019 KN
shutter as previously.
Do not dismantle the choke shutter, as otherwise the
factory default setting will no longer be correct and
this can lead to impaired engine performance. . Orient the new limiter cap (1) so that the
notch (arrow) points vertically upward
. Press the limiter cap (1) onto the high speed
screw (H) until it engages in the first position –
nearly flush with the dome (arrow) – do not
press it in all the way
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)m~ge 12 Technical Information 25.2010
. Install the carburetor Once the maximum speed of 13,000 rpm is
reached, do not continue to make the mix leaner –
the ignition module limits the maximum speed to
13,000 rpm. The permissible maximum speed
cannot be increased by continuing to make the mix
1 leaner. Making the setting too lean increases the
risk of engine damage.
6. Check the position of the limiter cap and
secure the limiter cap on the high speed
screw
5902TI022 KN 4.1.5 Checking the position of the limiter cap
. Insert the choke rod (1) in the opening and
move the master control lever toward the
position "Choke flap closed" l – the rod will
jump into the mount
. Install the air filter and shroud
1
. Let the engine warm up
Adjustment
Adjust the specified engine speeds within
a tolerance range of +/- 200 rpm as follows
5902TI023 KN
1. Set speed to 3,300 rpm with idle speed
adjusting screw (LA) . The notch (arrow) on the limiter cap must point
vertically upward
2. Turn the low speed screw (L) clockwise or
counterclockwise to set the highest speed.
If this speed is greater than 3,700 rpm, stop and
start again with step 1. 1
3. Set the speed to 3,300 rpm again with idle
speed adjusting screw (LA)
4. Set the speed to 2,800 rpm with low speed
5902TI020 KN
screw (L)
5. Set the speed to 13,000 rpm with the high
If the notch (arrow) on the limiter cap does not point
speed screw (H)
vertically upward
(starting with H = 1 1/2 turns open)
. Use a screwdriver to turn the limiter cap (1) as
far as it will go counterclockwise – notch (arrow)
points upward
. Continue with "Securing the limiter cap on the
high speed screw"
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Technical Information 25.2010 Page 13
4.1.6 Securing the limiter cap on the high 4.2 Fuel system – barbed connectors
speed screw To ensure the integrity of the fuel system:
. Pull or push the fuel hoses, by hand whenever
possible, in the direction of the connector in
order to avoid damage to the barbed connector
– sharp-edged pliers, screwdrivers, etc., may
not be used – also, do not cut open fuel hoses
with a knife or similar aids
. Do not reuse fuel hoses after removal. Always
replace them with new hoses – fuel hoses can
be overstretched during removal
5902TI021 KN
. Mount new fuel hoses dry or using press fluid
OH 723 – 0781 957 9000. Other press fluids are
. Use a 6 mm punch through the opening (arrow) not approved and may lead to fuel hose damage
to push the limiter cap until it is against the . Apply press fluid OH 723 to the ends of the hose
adjusting screws – the limiter cap is seated and the connectors and press the new hoses
approx. 2 mm inside the carburetor housing – onto the barbed connectors
limiter cap is secured
Notes regarding press fluid OH 723
4.1.7 Standard position Press fluid OH 723 produces a lubricant film that
simplifies assembly. The lubricant evaporates after
Using a standard carburetor screwdriver, carry out
a short time – the hose is firmly seated.
standard adjustment with limiter cap on the high
speed screw. Never use fuel, oil or grease as a lubricant. Fuel, oil
and grease do not evaporate – the hose may come
. Switch off the engine
loose.
. Check the air filter – clean or replace it if
necessary
. Check the spark arresting screen in the muffler
– clean or replace it if necessary
. Turn the high speed screw (H) counterclockwise
up to the stop (max. 3/4 turn)
. Carefully turn the low speed screw (L) clockwise
as far as possible, then back off 1 turn.
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)m~ge 14 Technical Information 25.2010
4.3 Tightening torques
The tightening torques for MS 271 and MS 291 are Code Type of Repair MS 271
listed in the Service Manual for STIHL MS 271, MS 291
MS 291.
1 Replace crankcase, crankcase 120
gasket or re-seal crankcase.
4.4 Service notes
Includes air leak test.
The Service Manual STIHL MS 271 and MS 291 is 2 Replace engine housing or 15
available for servicing and repair of the STIHL cylinder shroud.
MS 271 and MS 291.
3 Replace crankshaft main 110
bearing(s). Includes air leak
4.5 Serial number
test.
4 Replace crankshaft seal(s). 50
Includes air leak test.
5 Perform engine air leak test. 30
6 Replace cylinder and/or piston. 60
Includes air leak test and repair
of components causing failure.
7 Replace ignition module or 30
flywheel. Includes stop circuit
test.
0001TI007 KN
8 Replace fuel tank line, tank 25
vent, or fuel pick-up body.
9 Replace intake manifold or 30
The serial number is located to the side of the
intake flange, including leak
crankcase.
test.
4.6 Repair times 10 Repair or replace carburetor. 35
Includes fuel system testing.
The specified repair times assume that the work is
11 Replace fuel tank housing. 25
performed by trained personnel in a properly
equipped service workshop. 12 Replace oil pick-up/delivery 30
line. Includes oil output test.
Repair times are quoted in minutes.
13 Replace oil pump and/or drive 30
gear. Includes oil output test.
14 Replace rear handle frame or 25
handle housing.
15 Repair or replace rewind starte 20
16 Repair or replace clutch, clutch 20
shoes or clutch springs.
17 Repair chain break, including 35
check for proper function.
18 Replace muffler. 15
19 Replace air filter or filter 15
housing.
22 Repair or replace stop switch. 20
Includes circuit testing.
40 Miscellaneous repairs and 15
other repairs not listed.
45 Handling allowance only-no 10
labor.
50 No labor. 0
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Technical Information 25.2010 Page 15
© ANDREAS STIHL AG & Co. KG, 2010 Technical Documentation
D1/MTK-bl
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Extracted from the manufacturer's 2012 service catalogue. Most of these PDFs embed fonts with a shifted character map, so the text above was recovered rather than copied — read it as a faithful but imperfect transcription, and treat the page image above each block as the authority where the two disagree — the figures exist only there, because they are vector drawings that text extraction cannot keep.