Technical Information · issue 37 of 1998
BT 120 C: New Earth Auger
IssueTI 37/1998
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Technical Information
37.98
New Model BT 120 C Earth Auger - Series 4313
This new earth auger is a systematic further Applications are the same as for model BT 106.
development of the time-proven BT 106.
The engine installed in the BT 120 C is similar to
that of the FS 120. Page 2 of 6
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37.98 - 2 Contents 1. Technical Description 2. Technical Data 3. Augers 4. Special Accessories for Users 5. Service Accessories 6. Repairs 7. Spare Parts The following descriptions refer only to the differences over the BT 106. 1. Technical Description Powerhead • Newly developed STIHL single cylinder two-stroke engine. Cylinder • Four port technology (better mixture control, lower emissions). Carburetor • One adjusting screw (LD). • With compensator; increases filter efficiency by compensating for changes in pressure in the carburetor as filter becomes loaded with dirt. Air filter • Longlife air filter system with paper filter element. • Larger effective filter surface area. Easy start system • ElastoStart starter grip • Manual fuel pump Controls • New multi-function handle with soft, non-slip grip surface. Clutch • Two clutch shoes without linings. Auger brake • Manually operated auger brake Handle frame • New closed handle frame reduces vibration transmitted to handles.
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2. Specifications
2.1 Powerhead
2.1.1 Engine
Displacement: 30.8 cm3 (1.88 cu.in)
Bore: 35 mm (1.37 in)
Stroke: 32 mm (1.26 in)
Engine power to ISO 8893: 1.3 kW (1.8 bhp)
Engine speeds: see 2.1.2
Rewind starter: Single pawl system; ElastoStart grip
Starter rope: see 4.
Clutch:
- Clutch engages at: 4,300 rpm
2.1.2 Fuel System
Carburetor: All position diaphragm carburetor with integral fuel pump
Carburetor settings
Idle speed
1 Adjusting screw
2,800 rpm
Cut-off speed (rated) without auger 12,300 rpm
(electronic speed limiter)
Max. spindle speed (rated) 190 rpm
Fuel tank capacity: 0.64 l (1.35 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 Gearbox
Gear ratio: 47.5:1
2.3 Torque
Max. torque of drilling spindle: 79 Nm (58 ft.lb)
2.4 Weight
without auger 8.2 kg (18.1 lb) Page 4 of 6
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37.98 - 4 3. Augers The following augers are approved Part Name Part No. Earth auger; Ø 40 mm (1.6 in), 695 mm (27.4 in) long 4404 680 2004 Earth auger; Ø 60 mm (2.4 in), 695 mm (27.4 in) long 4404 680 2006 Earth auger; Ø 90 mm (3.5 in), 695 mm (27.4 in) long 4404 680 2009 Earth auger; Ø 120 mm (4.7 in), 695 mm (27.4 in) long 4404 680 2012 Earth auger; Ø 150 mm (6 in), 695 mm (27.4 in) long 4404 680 2015 Earth auger; Ø 200 mm (8 in), 695 mm (27.4 in) long 4404 680 2020 Planting auger; Ø 150 mm (6 in), 525 mm (20.6 in) long 4311 680 2515 Planting hole drill; Ø 260 mm (10.2 in) 4404 680 1900 4. Special Accessories for Users Part Name Part No. Application Shank extension 4311 680 2350 Extends auger fo Chuck 4311 680 4010 for drills up to 13 mm (0.5 in) diameter Padding 4311 748 2500 Cushions user’s thigh ElastoStart 0000 190 3400 Rewind starter (grip with rope) ElastoStart rope 0000 195 8200 Rewind starter STIHL gear lubricant Gearbox - 80 g/3 oz tube 0781 120 1117 4.1 Replacement Blades for Earth Augers Part Name Part No. Application Blade 4404 682 3101 Earth auger; Ø 60 mm (2.4 in) Blade 4404 682 3102 Earth auger; Ø 90 mm (3.5 in) Blade 4404 682 3103 Earth auger; Ø 120 mm (4.7 in) Blade 4404 682 3104 Earth auger; Ø 150 mm (6 in) Blade 4404 682 3105 Earth auger; Ø 200 mm (8 in)
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37.98 - 5 5. Service Accessories 5.1 Special Servicing Tools Special servicing tools are listed in the service manuals for models BT 106 (drilling gear) and FS 120 (engine). 5.2 Servicing Aids Part Name Part No. Application Carburetor parts kit 4134 007 1060 Zama C1Q-S36D Set of gaskets 4134 007 1050 BT 120 C Lubricating grease 0781 120 1111 Oil seals (370 g/13 oz tube) Dirko sealant 0783 830 2120 Crankcase sealing faces (100 g/3.5 oz tube) Hylomar sealing paste 0783 810 1101 Drlling gear sealing faces (100 g/3.5 oz tube) Standard commercial Cleaning crankshaft stub solvent-based degreasant containing no chlorinated or hydrogenated hydrocarbons 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 Carburetor Adjusting idle speed Important: Remove the auger from the machine before making the adjustment. • Check air filter and fit a new one if necessary. • Check spark arresting screen and clean or replace as necessary. • Start and warm up the engine. Engine stops when idling: Turn the idle speed screw (LD) slowly clockwise until the engine runs smoothly - drilling spindle must not rotate. Drilling spindle rotates when engine is idling Turn LD counterclockwise until drilling spindle stops rotating - then about another one full turn in the same direction from that position. 6.2 Tightening Torques Tightening torques are listed in the service manuals for models BT 106 (drilling gear) and FS 120 (engine).
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6.3 Service Note
Code Type of Repair BT 120 C*
For servicing and repair procedures on the
BT 120 C, refer to the service manuals for 1 Gear Unit –
models BT 106 (drilling gear) and FS 120 (engine).
These service manual do not include the chapters 2 Gear Unit Housing 0.6
“Servicing the Carburetor”, “Troubleshooting” or
any repairs involving standard procedures. Such 3 Bearings 1.0
procedures are described in separate handbooks.
4 Grease Seals 0.5
6.4 Repair Times 5 Pinion Shaft 0.4
The specified repair times assume that the work 6 Spur Gear & Driver 0.5
is performed by trained personnel in a properly
equipped service workshop.
The repair times are given in tenths of an hour
20 Misc. Repairs
✂ 0.5
(0.1 = 6 minutes).
Note: This table for the BT 120 C * For repair times for the BT 120 C engine, refer to
can be added to the STIHL repair times table. the repair times on FS 120 brushcutter
7. Spare Parts
An illustrated parts list is available for the new
model.
Andreas Stihl D1/MTK-sc 6381
© 1998 Andreas Stihl Technical Documentation 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.