background image

The following intervals apply for normal operating

conditions. The specified intervals must be short‐

ened accordingly when working for longer than nor‐

mal or under difficult cutting conditions (extensive

dust, etc.).

Before starting work

At the end of work and/or daily

Whenever tank is refilled

Weekly

Monthly

Annually

If faulty

If damaged

As required

Output regulating valve

check

X

X

Anti-vibration elements

check

X

X

X

Have replaced by serv‐

icing dealer

2)

X

Air intake screen

check

X

X

Clean

X

Safety information label

replace

X

1)

present only in some countries

2)

STIHL recommends STIHL dealers

19 Minimize Wear and Avoid

Damage

Observing the instructions in this manual helps

reduce the risk of unnecessary wear and dam‐

age to the power tool.
The power tool must be operated, maintained

and stored with the due care and attention

described in this owner's manual.
The user is responsible for all damage caused by

non-observance of the safety precautions, oper‐

ating and maintenance instructions in this man‐

ual. This includes in particular:

Alterations or modifications to the product not

approved by STIHL.

Using tools or accessories which are neither

approved or suitable for the product or are of a

poor quality.

Using the product for purposes for which it

was not designed.

Using the product for sports or competitive

events.

Consequential damage caused by continuing

to use the product with defective components.

19.1

Maintenance Work

All the operations described in the "Maintenance

Chart" must be performed on a regular basis. If

these maintenance operations cannot be per‐

formed by the owner, they should be performed

by a servicing dealer.

STIHL recommends that you have servicing and

repair work carried out exclusively by an author‐

ized STIHL servicing dealer. STIHL dealers are

regularly given the opportunity to attend training

courses and are supplied with the necessary

technical information.
If these maintenance operations are not carried

out as specified, the user assumes responsibility

for any damage that may occur. Among other

parts, this includes:

Damage to the engine due to neglect or defi‐

cient maintenance (e.g. air and fuel filters),

incorrect carburetor adjustment or inadequate

cleaning of cooling air inlets (intake ports, cyl‐

inder fins).

Corrosion and other consequential damage

resulting from improper storage.

Damage to the machine resulting from the use

of poor quality replacement parts.

20 Parts Subject to Wear and

Tear

20.1

Parts Subject to Wear and Tear

Some parts of the power tool are subject to nor‐

mal wear and tear even during regular operation

in accordance with instructions and, depending

on the type and duration of use, have to be

replaced in good time. Among other parts, this

includes:

Filters (air, fuel)

English

19 Minimize Wear and Avoid Damage

22

0458-372-0121-C

Summary of Contents for Sr 420

Page 1: ...SR 420 Instruction Manual 2 25...

Page 2: ...e machine or its individual components 1 3 Engineering improvements STIHL s philosophy is to continually improve all of its products For this reason we may modify the design engineering and appearance...

Page 3: ...use of the increased risk of accidents and damage to the power tool The product must not be modified in any way this may also lead to accidents or damage to the unit 2 3 Accessories and replacement pa...

Page 4: ...fumes or explo sive solutions Do not mix different plant protection products unless such a mixture is approved by the man ufacturer 2 5 2 Filling the Solution Container Stand the power tool securely...

Page 5: ...l quantities of fuel 2 8 Before starting Check that your power tool is properly assem bled and in good condition especially if it has been subjected to unusually high loads for which it was not design...

Page 6: ...charges Do not operate your machine on a non conduc tive surface e g plastic asphalt Never operate your machine with a missing or damaged discharge system Follow the mounting instructions supplied wi...

Page 7: ...r your power tool Com bustible fuel vapor may escape from the fuel sys tem If your power tool is subjected to unusually high loads for which it was not designed e g heavy impact or a fall always check...

Page 8: ...service or store your machine near open flames Check the fuel filler cap for leaks at regular inter vals Use only a spark plug of the type approved by STIHL and make sure it is in good condition see...

Page 9: ...4 to secure hose 1 and hose 3 to the stubs on the stop cock Close the stop cock move lever to vertical position Fill up with water and check all hose connec tions for leaks 3 4 Adjusting the Control...

Page 10: ...n lead to severe engine damage The engine seals fuel lines and fuel tank may be damaged if low quality gasoline or engine oil is used 5 2 1 Gasoline Use only high quality gasoline with an octane rat i...

Page 11: ...ilt up in the canister open it carefully The fuel tank and the canister in which fuel mixture is stored should be cleaned thoroughly from time to time Residual fuel and the liquid used for cleaning mu...

Page 12: ...r if the engine is not shut off in the idle position The throttle cable reconnects itself automatically when the setting lever is moved to the idle posi tion 8 Starting Stopping the Engine 8 1 Startin...

Page 13: ...ainst the base plate to prevent it slipping Hold the starter grip with your right hand Pull the starter grip slowly until you feel it engage and then give it a brisk strong pull NOTICE Do not pull out...

Page 14: ...ops simply multiply the length of the field by its width The surface area of high growing plants is calcu lated approximately by measuring the length of the rows and the average height of the foliage...

Page 15: ...ers by the time in minutes gives you the walking speed in meters per minute m min Example The distance covered in one minute is 10 meters Walking speed 10 m 10 m min 1 min 9 5 Determining discharge ra...

Page 16: ...666 1 747 1 700 2 2 928 2 896 2 864 ULV metering knob Discharge rate in l min Blower tube angle Knob set ting 30 0 30 0 5 0 142 0 132 0 128 0 65 0 216 0 212 0 203 0 8 0 352 0 403 0 377 10 5 Checking...

Page 17: ...06 KN Spray solution is finely atomized short broad and dense spray mist 12 2 Deflector Screen 372BA007 KN Diverts spray jet at an angle for under leaf treatment of low growing crops 12 3 Dual Deflect...

Page 18: ...lace if nec essary Check the spark arresting screen not in all models country specific in the muffler and clean or replace if necessary H L 373BA043 KN Carefully turn both adjusting screws counter clo...

Page 19: ...esting Screen in Muffler WARNING To reduce the risk of fire caused by hot particles escaping from the machine never operate the machine without a spark arresting screen or with the spark arresting scr...

Page 20: ...16 2 Checking the Spark Plug 000BA039 KN A Clean dirty spark plug Check electrode gap A and readjust if neces sary see Specifications Rectify the problems which have caused foul ing of the spark plug...

Page 21: ...ifficult cutting conditions extensive dust etc Before starting work At the end of work and or daily Whenever tank is refilled Weekly Monthly Annually If faulty If damaged As required Complete machine...

Page 22: ...sports or competitive events Consequential damage caused by continuing to use the product with defective components 19 1 Maintenance Work All the operations described in the Maintenance Chart must be...

Page 23: ...3 5 bhp Idle speed 3 100 rpm Engine blower speed dur ing operation 7 500 rpm 22 2 Ignition System Electronic magneto ignition Spark plug resistor type Bosch WSR 6 F NGK BPMR 7 A Electrode gap 0 5 mm 2...

Page 24: ...ribed in this User Manual The oper ating license shall be void if the engine is modi fied in any way 23 Maintenance and Repairs Users of this machine may only carry out the maintenance and service wor...

Page 25: ...ured in com pliance with the following standards in the ver sions valid on the date of production ISO 12100 EN 55012 EN 61000 6 1 EN ISO 28139 Technical documents deposited at ANDREAS STIHL AG Co KG P...

Page 26: ...English 25 EC Declaration of Conformity 26 0458 372 0121 C...

Page 27: ...25 EC Declaration of Conformity English 0458 372 0121 C 27...

Page 28: ...www stihl com 04583720121C 04583720121C 0458 372 0121 C 0458 372 0121 C...

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