Technical Information · issue 26 of 2002
New chainsaws STIHL MS 270 and MS 280
Models with QS chain brake system
IssueTI 26/2002
Engine family 1133
Full text
Page 1 of 14
Technical Information
26.2002
New chainsaws STIHL MS 270 and MS 280 – Series 1133
Contents
1. Technical description
2. Specifications
3. Service accessories and special tools
4. Service notes
5. Spare parts
S 270 C mit Kettenschnellspannung, Elastostart und
Dekompressionsventil
S 270 C mit Kettenschnellspannung, Elastostart und
Dekompressionsventil
S 270 C mit Kettenschnellspannung, Elastostart und
Dekompressionsventil
The new MS 270 and MS 280 chainsaws represent The newly designed anti-vibration system with one
the new mid-range. spring and three rubber elements lowers vibrations.
These light, compact chainsaws can be used for The ignition system with automatic adjustment of
many jobs on farms, in orchards and gardens, the ignition timing is designed for easier starting and
municipal service areas and by occasional users. optimum engine performance.
TI_26_2002_02_01_02.fm english / USA
)m~ge 2 Technical Information 26.2002
The MS 270 and MS 280 are available in two Ignition
versions (not in all markets):
. Ignition system with automatic adjustment of the
. Standard version ignition timing
. MS 270 C and MS 280 C with ElastoStart, chain Diaphragm carburetor with full-throttle partially
quick tensioning, decompression valve and QS fixed nozzle, part-throttle nozzle and contingent
chain brake, depending on the market versions idling
offered
. Limiter caps limit the adjustment range for the
high speed adjusting screw and low speed
1. Technical description adjusting screw (approx. 3/4 turn) to ensure
greater operational reliability and compliance
1.1 Power unit
with emission standards (refer to sections 4.1
STIHL single-cylinder two-stroke engine and 4.3)
. Accelerator pump for rapid acceleration (refer to
section 4.1.6)
Air filter
. Readily accessible, large area
. Optional mesh fabric filter for winter operation
. Standard felt filter for use in dry conditions with
high dust load
Muffler
. Two-chamber muffler with spark arresting
screen
Clutch
. With three unlined clutch shoes
146TI003 KN
1.2 Anti-vibration system
2
Cylinder
. Four-port system for better mixture control, and
optimum combustion
. Large cooling-air area
Crankcase
. Magnesium crankcase horizontally split parallel 2
to the crankshaft. The cylinder and upper half of
146TI004 KN
the crankcase form a single assembly
2 1
Piston
. Two piston rings for optimum performance over Depending on the type of equipment, the
a long service life combination with one spring (1) and three rubber
elements (2) reduces the level of vibrations (refer to
Crankshaft sections 4.2 and 4.3).
. Pressed together, built-up crank
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Technical Information 26.2002 Page 3
1.3 Tank caps
The new tank cap with hinged grip can be opened
and closed quickly and easily.
1.3.1 Opening 1.3.2 Closing
146TI005 KN
146TI007 KN
. Raise the grip until is upright . Fit the cap – grip upright – marks must line up
. fo
Turn the cap clockwise as far as stop
(approx. 1/4 turn).
n 146TI006 KN
146TI008 KN
. Turn the cap counterclockwise
(approx. 1/4 turn)
. Remove the filler cap . Fold the grip flush with the top of the cap
The tank cap is correctly engaged when the lug on
the grip engages in the recess (see arrow in right-
hand diagram).
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)m~ge 4 Technical Information 26.2002
1.4 Winter operation 1.5 QS chain brake system
Functional description
On models with QS chain brake system, the throttle
trigger interlock simultaneously serves as actuator
for the QS chain brake system.
150TI003 KN
146TI009 KN
When the trigger interlock is pressed while the
machine is running, the clutch drum is released by
Carburetor preheating
Preheated air from the cylinder flows into the
the brake band – and the saw chain can move.
carburetor through the opening cleared by the slide
and heats the carburetor. Preheated air does not
flow into the intake duct – thus ensuring high
volumetric efficiency.
Operation
150TI004 KN
As soon as the trigger interlock is released, the
brake band encloses the clutch drum – and the saw
chain comes to a halt within one second.
The chain brake can be triggered in three ways:
146TI017 KN
1
. Automatically by a sufficiently strong
kickback – due to the mass inertia of the hand
With a combination wrench or screwdriver, guard
. . Manually by pressing the front hand guard
turn slide (1) from the s position (summer) to
the r position (winter) – the slide must engage towards the bar tip
audibly . Manually by releasing the rear handle
The slide can be turned by hand after removing the
carburetor box cover.
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Technical Information 26.2002 Page 5
Note on chain lubrication
Chainsaws with QS chain brake system must be
lubricated with high-quality chain oil to ensure that
they operate reliably. Only STIHL Bioplus may be
used when using organic chain lubricants.
Unsuitable lubricants will lead to premature failure of
the chain brake due to resin build-up.
2. Specifications
2.1 Power unit
MS 270 MS 270 C MS 280 MS 280 C
Displacement 3.0 cu. in. (49.6 cm3 ) 3.3 cu. in.(54.2 cm3)
Cylinder bore 1.73 in (44.0 mm) 1.81 in (46.0 mm)
Piston stroke 1.28 in (32.6 mm)
fo 1.28 in (32.6 mm)
Power output to ISO 7293 3.49 bhp (2.6 kW) 3.75 bhp (2.8 kW)
Approx. Idle speed 2 800 rpm 2 800 rpm
Permissible max. speed
with bar and chain 13,500 rpm 13,500 rpm
Weight 11.7 lbs (5.3 kg) 11.9 (5.4 kg) 11.7 (5.3 kg) 11.9 (5.4 kg)
without bar and chain 12.1 (5.5 kg 1)) 12.1 (5.5 kg 1))
1)
Models with QS chain brake system
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)m~ge 6 Technical Information 26.2002
2.2 Fuel system 2.3 Ignition system
Carburetor: All-position diaphragm carburetor Ignition module: Electronically controlled
with adjustment of the
ignition timing
Idle speed adjusting Spark plug NGK BPMR 7 A
screw L (standard setting): 1/4 turn (interference
(max. to stop) suppressed):
High speed adjusting Electrode gap: .020 in. (0.5 mm)
screw H (standard setting): 3/4 turn
(max. to stop)
Maximum speed with bar 2.4 Chain lubrication
and chain: 13,500 +/– 1,500 rpm
Oil pump: Speed-dependent,
Fuel tank capacity: 17.5 oz. (0.52 l)
all-automatic pump with
rotary piston
Fuel mixture Oil tank capacity: 9.4 oz. (0.28 l)
Brand name mid-grade gasoline (89 octane
minimum) brand name two-stroke engine oil for
air-cooled two cycle engines. 2.5 Cutting attachment
Bar lengths: 16 in. through 20 in.
Engine oil
Only high-quality two-stroke air-cooled engine oil
fo Rollomatic
Oilomatic saw chains: 26 RM2
may be used – preferably STIHL two-stroke engine
(Rapid-Micro 2)
oil, as this is specially adapted to STIHL engines.
Chain pitch: .325“
Mixing ratio
Drive link gauge: .063“
1 : 50 when using STIHL two-stroke engine oil.
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Technical Information 26.2002 Page 7
3. Service accessories and
special tools
3.1 Service accessories
Item Part number Use
Set of carburetor parts 1128 007 1066 Repairing the carburetor
Dirko HT red sealant 0783 830 2000 Sealing the crankcase
Grease (225 g tube) 0781 120 1111 Oil seals, oil pump drive, sprocket bearings, chain tensioner
Bearing and sliding surfaces for throttle trigger, switch lever,
brake lever and trigger interlock
3.2 Special tools
Only the available special tools are required for
models MS 270 and MS 280.
The required special tools are listed in the repair
manual for STIHL MS 270 and MS 280.
3.3 Special accessories for the user
Item Part number Use
Cover plate 1133 080 7500 The slits in the fan cover can be partly covered to prevent
powdered snow from entering the machine in extreme winter
conditions, (temperatures below 15 °F (–10 °C).
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)m~ge 8 Technical Information 26.2002
4. Service notes 4.1.2 Maintenance / repair
The specific national safety regulations and the
safety instructions in the User's Manual must be
observed when starting and operating the chainsaw.
4.1 Carburetor adjustment
H L
146TI012 KN
258° 258°
The limiter caps must be removed in order to
replace an adjusting screw or to clean the
carburetor.
146TI011 KN
. Turn the limiter cap on the high speed adjusting
screw (H) counterclockwise as far as possible –
With this carburetor, the high speed adjusting screw ridge on limiter cap must line up with groove in
H and the low speed adjusting screw L can only be carburetor housing
adjusted by the user within a range of 258° .
Turn the limiter cap on the low speed adjusting
(approx. 3/4 turn). screw (L) clockwise – as far as possible – then
In this way, the carburetor setting can be adjusted to back off 1/4 turn – ridge on limiter cap must line
different working conditions, e.g. change of altitude up with groove in carburetor housing
(mountain country or sea level). . Turn extractor 5910 890 4500 counterclockwise
until the limiter cap is pulled off the head of the
4.1.1 Mechanical design adjusting screw
Adjustment after maintenance / repair
. Check air filter – clean or replace if necessary
. Check spark arresting screen – clean or replace
if necessary
3
1 . Inspect fuel filter-replace if necessary
146TI010 KN
4 2
. Limiter caps (1)
. High speed adjusting screw with seal (2)
. Low speed adjusting screw with seal (3)
. Idle speed adjusting screw (4)
The limiter caps are fitted over the knurled head of
the adjusting screws. The stops on the carburetor
housing serve as limiters.
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Technical Information 26.2002 Page 9
4.1.3 Basic setting without limiter caps 4.1.4 Securing the limiter caps
H L 1
146TI013 KN
146TI014 KN
. Starting from the lightly seated position of the Limiter caps must not be reused.
adjusting screw:
. Insert new limiter caps in the hole as
on MS 270 / C
illustrated – ensure that the ridges are correctly
positioned (see arrows)
H = Back off 11/8 turns
. Press the limiter caps onto the adjusting screws
L = Back off 11/4 turns until they are flush with the carburetor
on MS 280 / C
housing (1)
H = Back off 11/4 turns
L = Back off 11/4 turns
Set the specified speeds within the tolerance range
of +/– 200 rpm.
1. Set speed to 3300 rpm with idle speed adjusting
screw (LA).
2. Turn the low speed adjusting screw (L) clockwise
or anticlockwise to set the highest speed.
If this speed is greater than 3700 rpm, stop and start
again with step 1.
3. Set the speed to 3300 rpm again with idle speed
adjusting screw (LA).
4. Set the speed to 2800 rpm with low speed
adjusting screw (L).
5. Set the maximum speed of 13,500 rpm with the
high speed adjusting screw (H).
If the setting is too lean, the engine may be
damaged by overheating and a shortage of
lubricant.
6. Continue with "securing the limiter caps".
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)m~ge 10 Technical Information 26.2002
4.1.5 Standard setting with limiter caps Speed varies when idling; poor acceleration
The limiter caps must not be removed when making (despite low speed adjusting screw = 1/4)
the standard setting. . Idle setting too lean – turn low speed adjusting
. Switch off the engine screw (L) counterclockwise until the engine runs
uniformly and accelerates correctly – max. up to
. Check the air filter – clean or replace it if the stop
necessary
. Whenever the low speed adjusting screw (L)
. Check the spark arresting screen in the muffler has been adjusted, at least one adjustment
(if installed) – clean or replace it if necessary must be made on the idle speed adjusting screw
(LA)
Adjustment for use in mountain country or at
sea level
. A marginal adjustment may be necessary if the
engine does not run satisfactorily in mountain
country or at sea level:
. Check the standard setting
. Let the engine warm up
146TI015 KN
LA In the mountains:
. fo
Turn the high speed adjusting screw (H)
clockwise (leaner) – max. up to the stop
. Turn the high speed adjusting screw (H)
counterclockwise as far as possible (max. 3/4
At sea level:
turn)
. Turn the high speed adjusting screw (H)
. Turn the low speed adjusting screw (L) counterclockwise (richer) – max. up to the stop
clockwise – as far as possible – then back off
If the setting is too lean, the engine may be
1/4 turn
damaged by overheating and a shortage of
Idle speed adjustment lubricant.
Engine stops when idling
. Set the low speed adjusting screw (L) so that it
is 1/4 turn open
.
Turn the idle speed adjusting screw (LA)
clockwise until the saw chain begins to run –
then turn it back one turn
Chain runs when idling
. Set the low speed adjusting screw (L) so that it
is 1/4 turn open
. Turn the idle speed adjusting screw (LA)
counterclockwise until the chain stops – then
give it one more turn in the same direction
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Technical Information 26.2002 Page 11
4.1.6 Accelerator pump 4.2 Removing and fitting the handle tube
4 1
2
1
a 3
146TI018 KN
146TI016 KN
8
7
56
The carburetor is equipped with an accelerator . Remove shroud
pump. The pump piston (7) is located in the bore (a)
. Lift clip (1) off with a suitable screwdriver
behind the throttle shaft (4) and is held in the idle
position by a compression spring (8).
The bore (a) is sealed by a plug (5) in front of the
throttle shaft (4) to keep out dirt.
Disassembly of the accelerator pump
. Pry out plug (5) 1
. Undo screw (1)
. Remove throttle shutter (2)
146TI019 KN
. Remove snap ring (3)
. Seal bore (a) with a finger
. Push retainer (1) out through the handle tube
. Pull throttle shaft (4) back – until the end of the and remove it – the retainer on the ring buffer
throttle shaft appears in the carburetor throat prevents the buffer from being pulled out of the
. Carefully release finger from bore (a) – remove handle tube by very high handle forces
the ball (6), pump piston (7) with O-ring and . Undo the fastening screws at the sides and
spring (8) bottom
. Examine the pump piston (7) with O-ring and . Pry the plug and ring buffer under the plug out of
compression spring (8) – replace if damaged the handle tube – remove handle tube
. Reassemble the parts in reverse order . Install parts in reverse order
. Replace plug (5)
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)m~ge 12 Technical Information 26.2002
4.3 Fitting the spring
146TI020 KN
1 2
. Before installing the spring (1) and bushing (2),
they must be examined for signs of damage and
replaced if necessary
146TI021 KN
. The end of the spring winding must make
contact with the tank housing (arrow)
146TI022 KN
. Insert the spring and bushing in the serration of
the fan housing without tension
. Insert a 3/16“ dia. 5 mm drift in the bore (arrow)
– to prevent the bushing being forced out
. Turn in screw (1) and tighten down to a torque
of 35 inch pounds (4 Nm)
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Technical Information 26.2002 Page 13
4.4 Tightening torques .
The tightening torques for MS 270 and MS 280 are Code Repair activity MS 270
listed in the repair manual for STIHL MS 270 and MS 280
MS 280. 1 Crankcase, Crankshaft, Crank
Bearings, Crankcase 1.8
4.5 Service note Gasket/Seal Engine Pan
The repair manual STIHL MS 270 and MS 280 is 2 Cylinder Shroud, Engine Housing ---
available for servicing and repairing the STIHL 3 Front Handlebar/Handle Frame,
MS 270 and MS 280. Refer also to the STIHL Buffers 0.4
Service Training System "Diagnosis available on
4 Crankshaft Seals 0.9
CD-ROM".
5 Cylinder and/or Piston 1.8
4.6 Repair times 6 Ignition Module 0.5
The repair times are specified for trained personnel 7 Fuel Hose 0.4
and a fully equipped repair shop. 8 Carburetor Flange or Connector 0.4
9 Repair/Rebuild Carburetor 0.6
The repair times are specified in tenth of an hour
(0.1 = 6 minutes). 10 Replace Carburetor, Carburetor 0.4
Jet (If tried to repair use code 9)
The table of repair times for MS 270 and MS 280
11 Oil Pump, Oil Line 0.5
can be placed into the STIHL repair timetables
12 Recoil Starter 0.4
manual as a supplement.
13
fo Clutch 0.4
5. Spare parts 14 Chain Brake 0.5
15 Muffler 0.4
Separate spare parts lists are available for the new
16 Air Filter, Filter Cover, Tank Cap, 0.4
chainsaws.
Tank Vent, Fuel Filter, Oil Filter,
Spark Plug, Deco Valve, Cutting
Attachment, Miscellaneous Minor
Repairs
17 Stop Switch, Control Lever 0.4
18 Oil or Fuel Tank, 0.5
Tank/Handle Assy.
20 All other repairs 0.5
50 No Labor 0.0
✂
© 2002 Andreas Stihl AG & Co. Technical Documentation
Waiblingen D1/MTK-bl 7606
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)m~ge 14 Technical Information 26.2002
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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.