Technical Information · issue 19 of 2000
New Model HT 73 Pole Pruner
IssueTI 19/2000
Full text
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Technical Information
19.2000
New Model HT 73 Pole Pruner - Series 4142
Contents
1. Technical Description
2. Specifications
3. Cutting Attachment
4. Accessories
5. Service Accessories
6. Repairs
7. Spare Parts
The new low-emission STIHL HT 73 pole pruner
complies with the CARB II standards. It is built on
the basis of a new engine (series 4141 powerhead)
which features a new stratified charging system.
In this stratified charging system a layer of air
containing no fuel is laid in front of and partially over
the combustible mixture. This cushion of air results
in scavenging losses that are free from fuel (see “1.
Technical Description“).
The benefits are reduced environmental pollution
due to the very small proportion of unburnt fuel in
the exhaust gas and a lower fuel consumption.
The controls, handle system, drive tube, gearbox
and cutting attachment are exactly the same as
those of the HT 75.
Recommended applications are the same as those
of the HT 75.
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1. Technical Description
Controls, handle system, drive tube, gearbox and cutting attachment as on HT 75.
Stratified charged engine
380TI004 KN
Compression and induction
. A layer of air free from fuel is laid on top of the combustible mixture through additional reed valves in the
cylinder’s transfer ports
380TI005 KN
Combustion
. Crankcase pressure increases and causes the reed valves in the transfer ports to close
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Technical Information 19.2000 Page 3
380TI006 KN
Scavenging the cylinder (inlet)
. The fuel-free layer of air flows into the cylinder first
380TI007 KN
Scavenging the cylinder (outlet)
. Scavenging losses consist mainly of air that contains no fuel
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380TI008 KN
Induction and compression
. Reed valves in cylinder’s transfer ports open again
2. Specifications
2.1 Powerhead
2.1.1 Engine
Single cylinder two-stroke engine
Displacement: 25.4 cm3 (1.55 cu.in)
Bore: 34 mm (1.34 in)
Stroke: 28 mm (1.10 in)
Engine power to 0.9 kW (1.2 bhp)
ISO 8893: at 7,000 rpm
Engine speeds: see 2.1.2
Rewind starter: Single pawl system
Starter rope: 3 mm (0.12 in) dia.,
800 mm (31.5 in) long
Clutch engages at: 4,100 ±200 rpm
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Technical Information 19.2000 Page 5
2.1.2 Fuel System
Carburetor: All position diaphragm carburetor with integral fuel pump
Idle speed screw LA (standard setting) Open 6 full turns
Idle speed 3,000 rpm
Maximum engine speed without cutting attachment
- without speed governor 12,900 ±800 rpm
- with speed governor in ignition module 10,500 ±500 rpm
Fuel tank capacity: 0.7 L (700 cm3)
Fuel mixture: Mid grade (89 octane) brand-name unleaded gasoline and brand-name
two-stroke engine oill
Mix ratio: 50:1 with STIHL 50:1 two-stroke engine oil
2.1.3 Ignition System
Ignition module
- Start of production only: without speed governor
- All other production runs: with speed governor
Spark plug (suppressed): NGK CMR 7 A
0000 400 7007
Electrode gap: 0.5 - 0.6 mm (0.02 - 0.024 in)
Spark plug thread: M10x1.0
9.5 mm (0.375 in) long
2.2 Dimensions / Weight
2.2.1 Overall length
Shaft fully compressed - without cutting attachment: approx. 234 cm (7ft 8in)
- with cutting attachment: approx. 264 cm (8ft 8in)
Shaft fully extended - with cutting attachment: approx. 394 cm (12ft 11in)
2.2.2 Weight
- without cutting attachment: 7.0 kg (15.4 lb)
3. Cutting Attachment
Cutting length 30 cm (12 in); 3/8" Oilomatic Picco Micro Mini (PMN) chain, 44 drive links;
Rollomatic Mini guide bar; 7-tooth spur sprocket for 3/8"P, friction clutch for chain sprocket.
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4. Accessories
Part Name Part No. Application
Spark plug NGK CMR 7A 0000 400 7007 Engine
ElastoStart™ 0000 190 3400 Rewind starter (grip with rope)
Starter rope 0000 195 8200 Rewind starter, also for ElastoStart™
File holder 5605 750 4327 Sharpening the chain
including
- Round file, 5/32 in. dia. 5605 771 4006
Filing gauge 0000 893 4000
5. Service Accessories
5.1 Special Servicing Tools
The special servicing tools for the engine are listed in the service manual for the STIHL series 4141 powerhead.
For all other parts see service notes in TI 03.97 and TI 14.1999.
5.2 Servicing Aids
Part Name Part No. Application
Carburetor parts kit 4141 007 1002 Walbro WYA1
Set of gaskets 4141 007 1003 Carburetor
STIHL gear lubricant for
brushcutters Gearbox
- 80 g (2.8 oz) tube 0781 120 1117
- 225 g (8 oz) tube 0781 120 1118
Lubricating grease 0781 120 6602 Splined shaft in flexible liner (contact surfaces of
- 40 g (1.4 oz) tube external splined shaft and flexible liner)
Lubricating grease 0781 120 1111 Oil seals
- 225 g (8 oz) tube
Electrician’s repair kit 5910 007 1050 Electrical system
Standard commercial solvent- Cleaning crankshaft stub
based degreasant containing no
chlorinated or hydrogenated
hydrocarbons
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Technical Information 19.2000 Page 7
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 Adjustment
Standard setting
. Check chain tension.
. Check air filter and fit a new one if necessary.
. Inspect spark arresting screen and clean or
replace as necessary.
. Carefully back off the idle speed screw (LA)
counterclockwise until the end of the screw
(arrow) just disappears, then turn it six full turns
clockwise.
LA
Adjusting idle speed
. Carry out standard setting.
. Start and warm up the engine.
Engine stops while idling:
. Turn the idle speed screw (LA) slowly clockwise
until engine runs smoothly - the chain must not
rotate.
Saw chain runs while engine is idling:
. Turn the idle speed screw (LA) counter-
clockwise until the chain stops rotating and then
380TI010 KN
turn the screw about another two full turn in the
same direction (counterclockwise)
6.2 Tightening Torques
The tightening torques for the powerhead are listed in the service manual for the STIHL series 4141
powerhead. For all other parts see the service notes in technical information bulletins 03.97 and 14.1999.
Warning! Tighten spark plug to max. 15 Nm (11lbf.ft) only when the engine is cold.
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6.3 Service Note
The service manual for the STIHL series 4141 Code Type of Repair HT 73
powerhead can be used for servicing and repair 1 Crankcase, Crankshaft, 2.0
procedures on the HT 73 powerhead. For all other Crankshaft Bearings
parts see the service notes in technical information
2
bulletins 03.97 and 14.1999.
3 Crankcase, Gasket/Sealing 2.0
This service manual does not include the chapters
4 Crankshaft Seals 1.0
"Servicing the Carburetor", "Troubleshooting" or any
(Includes pressure and vacuum
repairs involving standard procedures. Such
testing)
procedures are described in separate handbooks,
5 Cylinder and/or Piston 1.2
i.e. “Carburetors” and "Standard Repairs,
Troubleshooting". 6 Ignition Module 0.5
7 Fuel Hose 0.5
6.4 Repair Times 8 Replace Gear Box Assy. 0.5
The specified repair times assume that the work is 9 Repair/Rebuild Carburetor 0.8
performed by trained personnel in a properly 10 Replace Carburetor 0.4
equipped service workshop. (If tried to repair use code 9)
11 Front Handle, Throttle Control, 0.6
Throttle Cable
The repair times are given in tenths of an hour.
12 Recoil Starter 0.5
(0.1 = 6 minutes).
13 Clutch, Clutch Drum, Clutch Drum 0.7
Housing
Note: This table for model HT 73 can be added to 14 Drive Tube, Drive Shaft, Drive 1.0 *
the STIHL repair times table. Shaft Bearings
15 Muffler 0.4
16 Air Filter, Filter Cover, Tank Cap, 0.4
Fuel Filter, Spark Plug, Cutting
Attachment, Miscellaneous Minor
7. Spare Parts Repairs
A separate illustrated parts list is available for the 17 Stop Switch 0.5
HT 73. 18 Fuel Tank, Oil Tank 0.4
19 Repair Gear Box, Gears, Arbor 0.7
Bearings, Oil Pump
20 All Other Repairs 0.5
✂
* If using a complete assembly to replace drive shaft
or outer support tube on HT 73, use code 20.
© 2000 Andreas STIHL AG & Co. Technical Documentation
Waiblingen D1/MTK-na 6940
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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.