Technical Information · issue 17 of 1996
New hedge trimmers HS 75, HS 80, HS 85
IssueTI 17/1996
Full text
Page 1 of 7
Technical Information
17.96
New hedge trimmers STIHL HS 75, 80, 85 - type 4226
)Technical Information 17.96 - Page 2
The hedge trimmers HS 75, 80, 85 replace the es-
tablished HS 72, 74 and 76 models. They have a
more powerful powerhead. With a displacement of
25.4 cm3 (1.55 cu. in), these machines have a hig-
her torque; with 0.9 kW (1.2 HP), they are also more
powerful than their predecessors.
The fields of application and target groups for the
HS 75, 80, 85 are identical with those of the
HS 72, 74 and 76.
Two different carburetor types may be installed in
the new models:
a) The conventional WT carburetor (made by
Walbro) with two adjusting screws (H and L)
as in the past.
and
b) A fixed-nozzle carburetor (made by Zama)
without high-speed adjusting screw; this
carburetor already meets the stringent
US emission standards and is designed to
reduce CO and HC emissions.
Note: Only the carburetors mentioned under b
are available for use in California at this time.
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1. Technical description
2. Specifications
3. Special accessories for the user
4. Service accessories
5. Repairs
6. Replacement parts
1.====Technical description
The main changes in comparison with the STIHL HS
72, 74, 76 are as follows:
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• Made up of five parts which are interconnected so
they cannot twist
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• Four-channel transfer ports (more effective prepa-
ration of the fuel mixture, optimum combustion, lo-
wer emission levels)
• Larger cooling area
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• With one or two adjusting screws
(see carburetor table)
)Technical Information 17.96 - Page 3
Air filter
• Improved filter material with longer service life
• Larger filter volume
Exhaust muffler
• Twin-chamber muffler
• Easier installation and removal of the spark arre-
sting screen
Starter mechanism
• ElastoStart handle for softer starting
2.=====Specifications
2.1====Engine
2.1.1=Power unit
Displacement: 25.4 cm3 (1.55 cu. in)
Bore: 34 mm (1.34 in)
Piston stroke: 28 mm (1.10 in)
Power output to ISO 8893:
Maximum speed:
0.9 kW (1.2 HP)
(see carburetor table)
Idle speed: (see carburetor table)
Starter mechanism: Single-pawl system; ElastoStart
Starter rope:
Diameter 3.0 mm (0.12 in)
Length: 800 mm (31.5 in)
Rewind spring:
Tension: 7 turns of the rope rotor
Reserve pull: At least 1/2 turn
Noise attenuation: Intake noise muffled
)Technical Information 17.96 - Page 4
2.1.2=Fuel system
Carburetor: All-position diaphragm carburetor with integral fuel pump
A C
rin 366TI004 KN
366TI003 KN
Carburetor WT 412 =WALBRO========================================Carburetor C 1Q S-29 =ZAMA
A = Valve nozzle B = Fixed idle-speed nozzle, dia. 0.32 mm
C = Valve nozzle with integrated fixed
nozzle, dia. 0.42 mm
Settings==============================WT 412========================C 1Q S-29
=================================================made by Walbro==================made by Zama
Low-speed adjusting screw1)
L = Back off 1 turn L = Back off 1 turn
Idle speed 2800 rpm 2800 rpm
High-speed adjusting screw1) H = Back off 1 turn None
Fuel tank capacity: 0.37 l (12.5 oz.)
Fuel mixture: Regular brandname gasoline and STIHL two-stroke engine oil
Octane number: At least 89 octane
Mix ratio: 1:50 for STIHL two-stroke engine oil 1:50
*1:25 for all other brandname two-stroke engine oils
Air filter: Foam insert and felt filter
G Only=two-stroke engine oils with a mixing ratio of 1:50 may be used in California!
2.1.3=Ignition system
Air gap: 0.2 ... 0.5 mm (0.008"-0.019")
Ignition timing: 1.55 ... 2.25 mm (0.061"-0.089")before TDC at n = 8000 rpm
Length of ignition lead: 160 mm
Spark plug (suppressed): Bosch WSR 6 F
Heat range: 200
Electrode gap: 0.5 mm (0.20")
Spark plug thread: M 14 x 1.25, length 9.5 mm
)Technical Information 17.96 - Page 5
2.2=Weight
(complete machine): HS 75/16" = 11.5 lbs.
HS 75/21" = 11.9 lbs.
HS 80/21" = 12.1 lbs.
HS 80/27" = 12.6 lbs.
HS 85/21" = 11.7 lbs.
HS 85/27" = 12.1 lbs.
HS 85/39" = 13.0 lbs.
* Cutter length
3.=======Special accessories for the user
Catcher plate for HS 85 4226 740 3350
4.=======Service accessories
4.1======Special tools
4.1.1=To be purchased for the first time for series HS 75, 80, 85
Designation=================Part No.=============Use=====================================Remarks
Axial face seal
Puller 5910 890 4400 Oil seals 1)
Spindle 5910 890 8400
1)
In the case of puller 0000 890 4400, the former spindle can be replaced by spindle 5910 890 8400,
which is 20 mm longer. The puller is then identical with puller 5910 890 4400.
4.1.2=Existing special tools
The usual special tools must be used for all other repair work (as for HS 72, 74, 76).
4.2======Aids
Carburetor parts kit 4133 007 1060 (WT 412) WALBRO
Carburetor parts kit 4226 007 1060 (C 1Q S-29) ZAMA
Gasket panel 0457 281 4203
5.====Repairs
The national safety regulations and the safety instructions in the Instruction Manual must be observed if the
machine has to be started up during maintenance or repair work.
5.1=Test values
5.1.1=Leakage test
Power unit
Leakage testing of the crankcase:
under pressure: 0.5 bar
under vacuum: 0.5 bar
&DUEXUHWRU
Inlet needle testing
pressure: 0.6 bar
)Technical Information 17.96 - Page 6
5.1.2=Adjustment of carburetor
======C 1Q S-29 =made by Zama
This carburetor does not include an adjusting screw for maximum speed (H screw), as adjustment of the ma-
ximum speed is not required.
The carburetor is tuned so that the engine is supplied with the optimum fuel/air mixture in all operating condi-
tions. Setting a maximum limit for the idle speed mixture also limits the emissions at idle speed and
part-throttle operation.
Standard setting
L = _~ck off 1=turn
• Check cutters - clean if necessary
(must be clean, move easily, not deformed)
• Check air filter - clean if necessary
• Let engine run until operating temperature is rea-
ched
L =`~refully turn the low-speed adjusting screw
clockwise as far as possible, then back off one turn
counterclockwise (standard setting L = 1F.
Set the idle speed to 2800 rpm via /$ = idle-speed
adjusting screw. fo
The following settings must be made if the
standard setting yields erratic engine behaviour
e.g. engine stops when idling, poor acceleration=!
Poor acceleration or engine stops after prolon-
ged idling
a) Adjust to standard setting EL = 1F>
bF=L = qurn low-speed adjusting screw one
quarter turn counterclockwise
c) Adjust the idle speed to approx. 2800 rpm by
means of the /$ = idle-speed adjusting screw
Repeat adjustments b) and c) if necessary!
Engine stops when swivelling, when changing
from full throttle to idle speed or runs erratical-
ly when idling
a) Adjust to standard setting EL = 1F>
b) Turn low-speed adjusting screw one eighth-turn
clockwise
c) Adjust the idle speed to 2800 rpm by means
of the /$ = idle-speed adjusting screw
Repeat adjustments b) and c) if necessary!
Cutting blades run while engine is idling
a) Adjust idle speed to 2800 rpm by means of
the /$ = idle-speed adjusting screw
b) /$ = Turn idle-speed adjusting screw
one half turn counterclockwise until cutting
blades no longer run when engine idles,
then add another half turn in same direction.
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The same adjustment as for the former WT 264 must be made for carburetor WT 412.
)Technical Information 17.96 - Page 7
5.1.3=Tightening torques
Fastener Thread size For component Tightening
torque (Nm)
Spline screw IS-M 5x25 Crankcase 9.5
Spline screw IS-M 5x25 Crankcase
Crankcase spacer flange/cylinder 5.5
Spline screw IS-DG 5x24 Cylinder/crankcase 9.5
Spline screw IS-M 4x16 Brake band/gear housing 3.5
Spline screw IS-M 4x16 Gearbox cover/gear housing 3.5
Spline screw IS-M 5x16 Muffler/cylinder 9.5
Spline screw IS-M 5x16 Air cowling/gear housing 5.5
Spline screw IS-M 5x16 Gear housing/crankcase 5.5
Spline screw IS-M 5x16 Starter cover/crankcase 5.5
Spline screw IS-M 5x16 Muffler/crankcase 9.5
M8 Starter carrier 20.0
Nut M8 Clutch 21.0
Spline screw IS-M 4x20 Ignition module/cylinder 4.5
Plastoform screw IS-P 5.5x12 Rope rotor in starter cover 3.5
Spline screw IS-M 5x16 Cutting blade 9.5
Spline screw
Spline screw
IS-M 5x20
IS-M 5x25
Blade guide/gear housing (HS 75, 80)
Blade guide/gear housing (HS 85)
9.5
9.5
Spline screw IS-M 5x25 Eccentric lever/gear housing 5.5
Spline screw IS-M 5x18 Rubber buffer/
handle moulding (HS 75, 80) 3.5
Spline screw IS-M 5x16 Rubber buffer/gear housing (HS 85) 5.5
Spark plug M 14x1.25 20.0
Plastoform screw IS-P 4x19 Handle moulding (HS 75, 80) 2.0
Spline screw IS-M 5x30 Handle halves (HS 85) 2.5
5.2=Repair times
The same repair times apply for the HS 75, 80, 85
models as for the HS 72, 74 and 76 models.
6.=Replacement parts
A separate parts list is available for the new mo-
dels.
Andreas Stihl - D1/MTK-al
© 1996 Andreas Stihl Technical Documentation 5773 Page 2 of 7
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