Technical Information · issue 34 of 1998
New Backpack Brushcutter FR 85
Model Tool Sound pressure Sound power Vibration Vibration
IssueTI 34/1998
Full text
Page 1 of 6
Technical Information
34.98
New FR 85 Backpack Brushcutter - Series 4137
The new lightweight semi-professional FR 85 The recommended applications are the same as
backpack brushcutter rounds off the lower end of those for models FR 350 and FR 450.
the line.
The engine installed in the FR 85 is exactly the The ergonomically designed controls, good power
same as that of models FS 75, 80, 85. to weight ratio and the new comfortable support
Support frame and shaft are the same as those frame offer professional-type handling and ensure
used in models STIHL FR 350 and 450. less fatigue over long periods of operation.
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Contents
1. Technical Description
2. Specifications
3. Cutting Tools
4. Special Accessories for Users
5. Service Accessories
6. Repairs
7. Spare Parts
1. Technical Description
Crankshaft
• Consisting of five parts pressed together to form a torsionally rigid assembly.
Cylinder
• Four port technology (better mixture control, clean combustion, lower emissions).
• Larger cooling area.
Carburetor
• With two adjusting screws (L, LA). fo
Air filter
• Improved filter material with longer life.
• Larger effective filter surface area.
Exhaust muffler
• Dual-chamber muffler.
Easy start system
• ElastoStart starter grip
• Manual fuel pump
Controls
• Multi-function handle with soft, non-slip grip surface.
Clutch
• Three clutch shoes without linings.
Drive shafts
• Flexible shaft and drive tube with rigid shaft running in a protective liner.
AV system
• Newly developed three-point AV system with springs.
Support frame
• Newly developed comfortable backpack system: Support frame with integral hip belt -
utilizes hip as supporting element to relieve load on shoulders and spine.
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2. Specifications
2.1 Powerhead
2.1.1 Engine
Displacement: 25.4 cm3 (1.55 cu.in)
Bore: 34 mm (1.34 in)
Stroke: 28 mm (1.10 in)
Engine power to ISO 8893: 0.9 kW (1.2 bhp)
Engine speeds: see 2.1.2
Rewind starter: Single pawl system; ElastoStart grip
Starter rope: see 4.
Clutch:
- Clutch engages at: 3700 rpm
Model Tool Sound pressure Sound power Vibration Vibration
level Lpeq level Lweq measurement measurement
to ISO 7917 1) to ISO 108841) to ISO 7916 to ISO 7916
Idle speed (m/s2) Max. RPM (m/s2)
Handle Handle
dB (A) dB (A) right left right left
FR 85
FR 85
Cutting head
Metal tool
95
89
110
103
fo 0.7
0.7
0.4
0.4
2.3
3.0
2.7
2.3
1)
Weighted equivalent level includes idling and racing with the same duration of exposure
2.1.2 Fuel System
Carburetor: All position diaphragm carburetor with integral fuel pump
Carburetor settings
Low speed adjusting screw L (standard setting) Open 1 full turn
Idle speed 2800 rpm
Cut-off speed range without cutting tool 9700 to 11300 rpm
(electronic speed limiter)
Max. output shaft speed (rated) 7500 rpm
Fuel tank capacity: 0.44 l (0.92 US pt)
2.1.3 Ignition System
Ignition module: with integral electronic speed limiter
Spark plug (suppressed): Bosch WSR 6F, NGK BPMR 7 A or Champion RCJ 6Y
2.2 Gearhead
Gear ratio: 1.4
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2.3 Weight
Without cutting tool and deflector: 9.4 kg (20.7 lb)
3. Cutting Tools
The following cutting tools are approved
1 STIHL Supercut 20-2 - 4002 710 2162
2 STIHL Autocut 21-2 - 4002 710 2113
3 STIHL Autocut 25-2 - 4002 710 2108
4 STIHL Polymatic 30-2 - 4002 710 2120
5 STIHL Trimcut 30-2 - 4002 710 2122
6 STIHL Polycut 20-3 - 4002 710 2130
7 Cutting blade 230-2 - 4001 713 3804
8 Cutting blade 230-4 - 4001 713 3801
9 Cutting blade 230-8 - 4001 713 3803
10 Brush knife 250-3 - 4112 713 4100
4. Special Accessories for Users
Part Name Part No. Application, Remarks fo
Transport guard for
Metal cutting tools 4119 790 3906 Cutting blade 230-2, 230-4, 230-8, brush knife 250-3
ElastoStart 0000 190 3400 Rewind starter (grip with rope)
ElastoStart rope 0000 195 8200 Rewind starter
STIHL gear lubricant Drive shaft, flexible shaft
- 80 g/3 oz tube 0781 120 1109
- 225 g/8 oz tube 0781 120 1110
STIHL gear lubricant Gearbox
- 80 g/3 oz tube 0781 120 1117
- 225 g/8 oz tube 0781 120 1118
STIHL special oil Rewind spring in starter,
- 100 ml/3.5 fl.oz bottle 0781 417 1315 bearing bore in rope rotor
4.1 Nylon Line for Cutting Heads
Line Application
Diameter / Color
2.4 mm/0.95" orange Supercut 20-2, Autocut 21-2, Autocut 25-2, Polymatic 30-2, Trimcut 30-2, Polycut 20-3
2.7 mm/0.105" red Polycut 20-3
4.2 Sharpening Aid for Metal Cutting Tools
Part Name Part No. Application
Sharpening template 4020 890 5500 Brush knife
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5. Service Accessories
5.1 Special Servicing Tools
Special servicing tools are listed in the service manuals for models FS 75, 80, 85 (powerhead) and
FR 350, 450 (shaft, support frame).
For further information on special tools see TI 36.96 (FS 75, 80, 85).
5.2 Servicing Aids
Part Name Part No. Application
Carburetor parts kit 4227 007 1060 Zama C1Q-S28C, C1Q-S41
Lubricating grease
(225 g/8 oz tube) 0781 120 1111 Oil seals
Dirko sealant
(100 g/3.5 oz) 0783 830 2120 Crankcase sealing faces
Standard commercial Cleaning crankshaft stub
solvent-based degreasant
containing no chlorinated
or hydrogenated hydrocarbons fo
6. Repairs
If the unit is started up in the course of repairs or maintenance work, it is essential to strictly
observe all local and national safety regulations and the safety precautions outlined in the
owner’s manual.
6.1 Setting Data
For carburetor adjustment see TI 41.97.
6.2 Tightening Torques
Tightening torques are listed in the service manuals for models FS 75, 80, 85 (powerhead) and
FR 350, 450 (shaft, support frame).
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6.3 Service Note No. Repair procedure FR 85
For servicing and repair procedures on the FR 85,
refer to the service manuals for models FS 75, 80,
85 (powerhead) and FR 350, 450 (shaft, support 1 Remove and refit engine 20
frame).
These service manuals do not include the chapters 2 Crankcase, pressure test* 110
“Servicing the Carburetor”, “Troubleshooting” or 3 Crankshaft, bearings, pressure
any repairs involving standard procedures. Such test* 110
procedures are described in separate handbooks,
4 Sealing rings, pressure test* 70
i.e. “Carburetors” and “Standard Repairs,
Troubleshooting”. 5 Crankcase leakage
test, test run 40
6 Cylinder, piston, pressure test* 55
6.4 Repair Times
7 Ignition system, contact* 10
The specified repair times assume that the work 8 Fuel supply, tank vent,
is performed by trained personnel in a properly test run 10
equipped service workshop.
9 Manifold or flange,
pressure test -
The repair times are given in minutes.
10 Carburetor, check* 30
Note: This table for the FR 85
can be added to the STIHL repair times table.
11
12
Handle and throttle control
Rewind starter, test run
10
15
13 Clutch, test run 20
14 Muffler 10
7. Spare Parts 15 Air filter 5
16 Stop switch, test run 10
An illustrated parts list is available for the new
model. 17 Clutch housing 20
18 Drive tube 25
19 Replace gearhead or
bearing housing 5
20 Limit stop or deflector 10
21 Drive shaft 15
22 Fuel tank 20
23 Check compression pressure -
24 Adjust valve clearance -
25 Replace crankcase,
bottom half -
26 Replace crankshaft -
27 Replace cylinder, piston -
28 Oil supply -
29 Oil pump, test run
✂ -
* Test run under load
© 1998 Andreas Stihl Andreas Stihl D1/MTK-na
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