Technical Information · issue 14 of 2006
New chain saws STIHL MS 441, MS 441 C-Q – Series
IssueTI 14/2006
Engine family 1138
Full text
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STIH)
Technical Information 14.2006
New chain saws STIHL MS 441, MS 441 C-Q – Series 1138
Contents
1. Technical description
2. Specifications
3. Special tools and service accessories
4. Service note
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High performance, low vibrations and light : these 1. Technical description
are the features characterizing the new professional
chain saw models MS 441 and MS 441 C-Q from 1.1 Principle of operation, stratified
STIHL. scavenging
The new STIHL two-stroke power unit with four-port A cushion of air (fuel-free air) separates the fuel-air
technology and stratified scavenging yields: mixture from the exhaust gas. This cushion of air is
- high power, located in front of the fuel-air mixture. At the start of
the exhausting and scavenging cycle, fuel-free air
- high torque over a wide range of speeds, first streams from the transfer ports into the
- distinctly lower fuel consumption – up to 20% as combustion chamber and scavenges the exhaust
compared with conventional two-stroke engines gas into the exhaust port. The air prevents the
subsequent fuel-air mixture from entering the
The MS 441 and MS 441 C-Q are designed and
exhaust port, thus reducing the fuel-laden
built for a wide variety of uses in timber harvesting
scavenging losses and the fuel consumption.
and general timber work.
The air filter system with pre-separation distinctly
extends the intervals between cleaning (filter life is 1.1.1 Mechanical design
roughly doubled in comparison to the MS 440).
The newly designed anti-vibration system provides
low vibrations.
The ignition system with electronic adjustment of the
ignition timing permits optimum performance, as
well as reducing exhaust emissions.
ElastoStart™ plus (i.e. ElastoStart™ starter handle
and decompression valve) allows convenient 4
starting.
The MS 441 is optionally available with heated 1
handles and carburetor heating.
The MS 441 C-Q additionally features a dual chain 2
brake system.
000TI043 KN
3
The fuel-air port (1) is separate from the fresh air
ports (2). An integrally moulded control slot (4) in the
piston skirt opens and closes the connection
between fresh air ports (2) and transfer ports (3).
Further components are not required for controlling
the intake of fresh air.
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Technical Information 14.2006 Page 3
1.1.2 Compression and intake
1
2 1
2 2
3 3
000TI044 KN
Fresh fuel-air mixture (--- arrows) streams into the crankcase. At the same time, the piston opens the fresh air
port (2) via the control slot (1) in the piston skirt and fresh air (: :: arrows) streams through the control slot into
the transfer ports (3). The fuel-air mixture in the combustion chamber is compressed.
1.1.3 Expansion and crankcase compression
000TI045 KN
Shortly before the piston reaches top dead center (TDC), the mixture is ignited by the spark plug.
The fresh air (::: arrows) in the transfer ports and the fuel-air mixture (--- arrows) in the crankcase are then
compressed as the piston travels downward.
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)m~ge 4 Technical Information 14.2006
1.1.4 Exhausting and scavenging
000TI046 KN
The piston continues its downward movement, opening first the exhaust port and then the transfer ports. The
fresh air (:: : arrows) streams into the combustion chamber and scavenges the exhaust gas (--- arrows) out
of the combustion chamber.
1.1.5 Return flow and scavenging
000TI047 KN
When the air has scavenged the exhaust gas (--- arrows) out of the combustion chamber almost completely,
fresh fuel-air mixture (--- arrows) streams in and mixes with the remaining air in the combustion chamber.
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Technical Information 14.2006 Page 5
1.2 Carburetor with additional air flap
a 3 b c d
6 3
5 7
4 2
4
000TI048 KN
a) Full throttle b) Part throttle c) Idle d) Cold start
Full throttle and part throttle Cold start
The air flap (1) controls the inflow of fresh air. It With the choke (4) closed in cold start position, the
opens as a function of the position of the throttle air flap is forcibly closed via the lever (5) on the
shutter (2). The specially shaped, curved path on choke shaft and the carrier (6) on the air flap shaft.
the lever (3) is needed for optimum scavenging and The lever (3) on the air flap shaft and carrier (7) on
an optimally tuned power unit. the throttle shutter shaft are deactivated. In the hot
start position, choke and air flap are marginally
Idle
open.
The air flap is closed. Fresh air is not drawn in at
idle. The result is uniform and stable no-load
operation.
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1.3 Air filter system with pre-separation 1.5 Winter operation
1 3
2
4
219TI008 KN
219TI012 KN
The air which has been drawn in is swirled and Carburetor preheating
deflected by the ramp in front of the ignition module. The carburetor carrier (1) and preheating plate (2)
The larger and heavier entrained particles (black form the preheating channel.
arrows) are catapulted upwards and outwards. The Preheated air from the cylinder streams into the
pre-cleaned air (grey arrows) streams through the preheating channel through the opening created by
pre-separation duct to the air filter. slide (3) and heats the preheating plate. The air
leaves through the opening (4). The carburetor is
1.4 Anti-vibration system heated by the preheating plate. Cold, pre-cleaned
air flows into the intake duct through the pre-
separation system, thus ensuring that the charge
remains unchanged.
The new anti-vibration system comprises the
springs (1) and (3), spring (2) with integrated
overload protection, the Cellasto anti-vibration
element (4) and the two Cellasto stop buffers (5).
This combination reduces the level of vibrations.
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Technical Information 14.2006 Page 7
1.6 Filler cap 2. Specifications
The filler cap can be opened and closed quickly and
easily: 2.1 Power unit
Large, readily accessible tank openings allow the STIHL single-cylinder two-stroke engine
machine to be refuelled easily.
Displacement 4.31 cu in. (70.7 cm3)
1.7 Dual chain brake system (MS 441 C-Q) Bore 1.97 in. (50 mm)
Stroke 1.41 in. (36 mm)
With this system, the chain sprocket is blocked
when in idle position. Power output to 5.5 hp (4.1 kW)
The throttle trigger interlock simultaneously serves ISO 7293 at 9,500 rpm
as actuating lever for the chain brake system. The Idle speed 2,800 rpm
brake band releases the clutch drum when the Permissible maximum
throttle trigger interlock is pressed. speed with guide bar and
chain 13,500 rpm
When the interlock is released, the brake band
clamps the clutch drum. Weight without guide bar
and chain
The chain brake can be triggered in three ways: MS 441 14.5 lb (6,60 kg )
- Automatically, by the inertia of the hand guard in MS 441 with heated
the presence of a sufficiently strong kickback. handles 14.7 lb (6,70 kg)
MS 441 C-Q 14.7 lb (6,70 kg)
- Manually, by pushing the front hand guard
towards the bar nose.
- Manually, by releasing the throttle trigger and
2.2 Ignition system
throttle interlock.
Ignition module Electronically controlled
with automatic ignition
timing adjustment
Spark plug
(suppressed) NGK BPMR 7 A
Electrode gap 0.020“ (0.5 mm)
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2.3 Fuel system 2.4 Chain lubrication
Carburetor Oil pump: Speed-dependent pump
All-position diaphragm carburetor with rotary piston –
additional manual oil flow
Standard setting with limiter caps control
Oil tank capacity: 0.76 US pt (0.360 litres)
Low speed adjusting 1/4 turn open
screw L (max. up to the stop)
2.5 Bar and chain
High speed adjusting 3/4 turn open Guide bar: Rollomatic, Duromatic
screw H (max. up to the stop) Oilomatic chains: Rapid Micro 2,
Rapid Micro,
Rapid Super,
Basic setting without limiter caps
Rapid Super C,
(during repairs)
Rapid Super C3
Low speed adjusting Chain pitch: 3/8"
screw L 1 turn open Chain sprocket: 7 teeth for 3/8"
(rim sprocket)
High speed adjusting 8 teeth for 3/8" (optional)
screw H 1 turn open (rim sprocket)
Fuel mixture
See owner's manual.
Fuel tank capacity: 1.53 US pt (0.725 litres)
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Technical Information 14.2006 Page 9
3. Special tools and service
accessories
3.1 Special tools
The following new special tools are needed.
1
3 2
5
4
901TI033 KN
Item Part name Part No. Use
1 Screwdriver 5910 890 2304 Basic setting of the adjusting screws with fitted limiter caps
2 Sleeve 5910 893 1706 Fitting hookless snap rings in piston
(supplementary to assembly tool 12)
3 Flange 1138 890 1200 Leakage testing
4 Sealing plate 0000 855 8107 Sealing the exhaust port
5 Mount 5910 850 1650 For attachment to the chain saw assembly stand
The sleeve supplementing assembly tool 12
(5910 893 1706) replaces the existing sleeve.
The existing special tools are listed in the service
manual STIHL MS 441.
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3.1.1 Rework note for crankcase tool The figure 20 must be stamped on the upper side,
Disk 5910 893 2101 from assembly tool alongside each of the new holes, for identification. A
kit ZS new notch must be produced in the edge of the disk
Assembly tool kits 5910 007 2200 supplied from and stamped with the figure 20.
factory will in the future include the modified disk
and already include three additional holes with
diameter 7/32“ (5.5 mm) for use with MS 441. An
existing disk without these holes can be reworked in
accordance with the template shown below.
21,3
34
20
20
38
33,1
20
3,2
39,3
49,9
2,3
10,4
39,3
901TI032 KN
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Technical Information 14.2006 Page 11
3.1.2 Rework note for crankcase tool
Assembly tool AS 5910 890 2205
The flange on the current assembly tool
5910 007 2205 has been prepared for the collar
screws of the MS 441. An older assembly tool
without the recesses around the holes can be
reworked as shown below.
5910 890 2205 C
901TI034 KN
The holes for locating the collar screws must be Only the modified assembly tools
modified for the MS 441 (tapered contour). AS 5910 007 2205 will be available in the future.
They are identified by the letter C after the part
number.
3.2 Service accessories
Part name Part No. Use
Set of carburetor parts 1128 007 1066 Repairing the carburetor
Lubricant grease 8 oz tube 0781 120 1111 Oil seals, oil pump drive, sprocket bearings, chain tensioner
(225 g tube) bearing and sliding points of the throttle trigger, brake trigger
and trigger interlock
STIHL special lubricating oil 0781 417 1315 Bearing bore in rope rotor, rewind spring in fan housing
Commercially available Cleaning the crankshaft stub and taper on flywheel
solvent-based degreasant
not containing any
chlorinated or halogenated
hydrocarbons
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3.3 Special accessories for the user
Part name Part No. Use
Cover plate kit 1138 007 1000 In extreme winter conditions (temperatures below 15 ° F or
-10 °C, powdery or drifting snow) – prevents powdery or
drifting snow from entering the machine
4. Service note 4.1.2 Basic setting without limiter caps
Specific national safety regulations and the safety
instructions in the owner's manual must be
observed if the chain saw has to be started up
during repairs.
4.1 Carburetor
H L
With this carburetor, the user can only adjust the
high speed screw H and low speed screw L within a
range of 258° (approx. 3/4 turn). This ensures that
146TI013 KN
the engine always operates at the best possible
setting for full throttle, part throttle and idle.
However, precision adjustments can still be made if
required on account of changed working or service . With the adjusting screw fully in its seat:
conditions, such as a change in altitude (mountains, Open H one turn
sea level). Open L one turn
4.1.1 Removal of the limiter caps
The limiter caps must be removed in order to 4.1.3 Fitting the limiter caps
replace a faulty adjusting screw or to clean the
carburetor.
Caps must not be reused after removal, as they
are damaged when pulled off!
219TI004 KN
. Fit new limiter caps in the bore as illustrated,
ensuring that the lugs are correctly positioned.
. Press the limiter caps onto the adjusting screws
until they engage for the first time.
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Technical Information 14.2006 Page 13
. Install the carburetor and continue with "Basic 4.1.5 Securing the limiter caps
setting with fitted limiter caps".
4.1.4 Basic setting with fitted limiter caps
219TI005 KN
. Push the limiter caps home on the adjusting
219TI011 KN
screws with a suitable punch inserted through
the holes in the grommet.
The adjusting screws are set to their basic setting
with the screwdriver 5910 890 2304 (special tool).
The screwdriver must be inserted through the
grommet and fitted limiter cap until it reaches the
adjusting screw.
The specified speeds are set with a tolerance
range of +/-200 rpm.
1. Set the idle speed screw (LA) to 3,300 rpm.
2. Turn the low speed screw (L) to the right or
left until the maximum speed is reached.
If this speed is over 3,700 rpm: start again with
step 1.
3. Set the idle speed screw (LA) to 3,300 rpm
again.
4. Set the low speed screw (L) to 2,800 rpm.
5. Now set the high speed screw (H) to the
maximum speed of 13,500 rpm.
If the setting is too lean, the engine may overheat
due to lack of lubrication!
6. Continue with "Securing the limiter caps".
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4.1.6 Standard setting with limiter caps Erratic idling; poor acceleration
The limiter caps must not be removed when making . Open the low speed screw (L) 1/4 turn.
the standard setting!
. Idle setting too lean – turn the low speed screw
. Switch off the engine. (L) counterclockwise until the engine runs
. Check the air filter and clean or replace it if smoothly and accelerates properly, but no
necessary. further than the stop.
. Check the spark arresting screen (if installed) in . At least one adjustment of the idle speed screw
the muffler and clean or replace it if necessary. (LA) will also be required whenever the setting
of the low speed screw (L) is corrected.
Correcting the carburetor setting for use at high
altitudes
A slight correction may be required if the engine
does not run satisfactorily:
. Check the standard setting.
. Let the engine warm up.
. Turn the high speed screw (H) clockwise
219TI006 KN
(leaner), but no further than the stop.
If the setting is too lean, the engine may overheat
due to lack of lubrication!
. Turn the high speed screw (H) counterclockwise
as far as the stop (max. 3/4 turn),
. Then turn the low speed screw (L) back 1/4 turn
clockwise, as far as the stop.
Set idle speed
. Open the low speed screw (L) 1/4 turn.
. Turn the idle speed screw (LA) clockwise as far
as the stop or until the chain starts to run, then
back off 11/2 turns.
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Technical Information 14.2006 Page 15
4.2 Air flap control The air flap must be checked before making any
carburetor settings or maintenance.
3
1
4 2
1
219TI009 KN
219TI013 KN
Screws (1), (2), (3) and (4) are bonded into place
and must not be unscrewed or removed. . The air flap (1) must fit snugly around the
Screws (1), (2) and adjusting screw (3) must not be housing wall in idle position and seal the air
adjusted, otherwise the factory setting will no longer duct.
be correct and the machine will no longer run . A soiled air flap should be cleaned with STIHL
smoothly. special cleaner or a non-flammable cleaning
agent, taking care not to damage the air flap.
4.2.1 Setting of the throttle shutter / air flap
The air flap control does not require any
adjustments. The correct setting of the air flap can 4.2.2 Pump diaphragm
be checked visually as follows.
Throttle shutter (trigger
position) Air flap
Idle Fully closed
Idle to full throttle Closed to fully open1)
Full throttle Fully open1)
Cold start l Fully closed
Hot start n Open approx. 10°
219TI010 KN
1)
It must be possible to move the air flap in both
directions (open and closed) and it must always
return to its starting position. End cover, pump diaphragm and gasket are
removed without dismantling or removing the air flap
housing.
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)m~ge 16 Technical Information 14.2006
4.3 Dual chain brake system The repair times are specified in minutes.
Chain saws with a dual chain brake system must be Repair Description MS 441
operated with high-quality chain lubricant in order to
1 Replace crankcase, crankcase 140
ensure reliable operation. If organic biogradeable
gasket or re-seal crankcase.
chain lubricant is to be used, only STIHL BioPlus
Includes air leak test.
may be used!
Unsuitable oils will lead to premature failure of the 2 Replace cylinder shroud. 15
chain brake due to resin build-up. 3 Replace crankshaft main bearing(s). 130
Includes air leak test.
4.4 Tightening torques 4 Replace crankshaft seal(s). Includes 60
air leak test.
The tightening torques for the MS 441 are specified
in the service manual STIHL MS 441. 5 Perform engine air leak test. 30
6 Replace cylinder and/or piston. 60
4.5 Service note Includes air leak test and repair of
components causing failure.
The service manual STIHL MS 441 is available for
servicing and repair of the STIHL MS 441. 7 Replace ignition module or flywheel. 25
Includes stop circuit test.
4.6 Serial No. 8 Replace fuel tank line, tank vent, or 25
fuel pick-up body.
9 Replace intake manifold or intake 25
flange, including leak test.
10 Repair or replace carburetor. 30
Includes fuel system testing.
11 Replace fuel tank housing. 35
12 Replace oil pick-up/delivery line. 20
Includes oil output test.
13 Replace oil pump and/or pump drive 20
gear. Includes oil output test.
219TI007 KN
14 Replace rear handle frame or 30
handle housing.
The serial number can be found on the side of the 15 Repair or replace rewind starter. 20
crankcase. 16 Repair or replace clutch, clutch 20
shoes or clutch springs.
4.7 Repair times 17 Repair chain brake, including check 35
The repair times are specified for trained specialist for proper function.
personnel and a fully equipped service repair shop. 18 Replace muffler. 15
19 Replace air filter or filter housing. 15
20 Replace heating element(s) on 25
"Arctic saws". Includes diagnostic
and function tests.
21 Replace generator on "Arctic" saws. 30
Includes diagnostic and function tests.
22 Repair or replace stop switch. 15
Includes circuit testing.
23 Replace throttle cable. 35
40 Miscellaneous repairs and other 15
repairs not listed.
45 Handling allowance only-no labor. 5
50 No labor. 0
© ANDREAS STIHL AG & Co. KG, 2006 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.