Husqvarna K 770 OilGuard Instruction manual

Workshop manual
K770
English
651 - 001 - 27.06.2018

Contents
1 Introduction
1.1 Document description............................................ 3
1.2 Target group...........................................................3
1.3 Revisions................................................................3
1.4 Safety..................................................................... 3
1.5 Servicing tools........................................................3
2 Safety
2.1 Safety definitions....................................................4
2.2 General safety instructions.....................................4
2.3 Symbols on the product......................................... 4
3 Servicing data
3.1 Symbols in the diagrams........................................5
3.2 Tightening torques................................................. 6
4 Servicing tools
4.1 Servicing tools overview.......................................10
4.2 Servicing tools overview.......................................11
4.3 Servicing tools overview.......................................12
5 Product overview for repair and servicing
5.1 Components.........................................................13
5.2 To disassemble into basic modules..................... 14
6 Repair and servicing
6.1 Starter.................................................................. 20
6.2 Ignition system..................................................... 23
6.3 Flywheel............................................................... 27
6.4 Air filter................................................................. 28
6.5 Fuel system..........................................................29
6.6 Carburetor............................................................ 31
6.7 Decompression valve...........................................40
6.8 Cylinder and piston.............................................. 41
6.9 Piston wear.......................................................... 44
6.10 To assemble the piston...................................... 45
6.11 To assemble the cylinder................................... 46
6.12 Crankcase.......................................................... 47
6.13 Clutch................................................................. 52
6.14 Cutting head.......................................................55
6.15 Wet system........................................................ 60
6.16 Throttle trigger and throttle lock......................... 61
6.17 OilGuard.............................................................62
7 Troubleshooting
7.1 Engine does not start........................................... 64
7.2 Engine stops during operation - no sparks...........65
7.3 Engine stops during operation............................. 65
7.4 Weak output or change of speed......................... 66
7.5 Other engine problems.........................................66
8 Wiring diagram
8.1 Wiring diagram OilGuard......................................67
2651 - 001 - 27.06.2018

1 Introduction
1.1 Document description
This manual gives a full description of how to do
maintenance and repair on the product. It also gives
safety instructions that the personnel must obey.
1.2 Target group
This manual is for personnel with a general knowledge
of how to do repair and do servicing. All personnel that
do repair or do servicing on the product must read and
understand the manual.
1.3 Revisions
Changes to the product can cause changes to the
maintenance work and spare parts. Separate
information is sent out for each change.
Read the manual together with all received information
about changes to maintenance and spare parts for the
product.
1.4 Safety
WARNING: All personnel that repair or do
servicing on the product must read and
understand the safety instructions in this
workshop manual.
1.5 Servicing tools
The manual gives information about necessary servicing
tools. Always use original tools from Husqvarna.
651 - 001 - 27.06.2018 Introduction - 3

2 Safety
2.1 Safety definitions
The definitions below give the level of severity for each
signal word.
WARNING: Injury to persons.
CAUTION: Damage to the product.
Note: This information makes the product easier to use.
2.2 General safety instructions
• Do not repair the product unless you have read and
understood this workshop manual.
• The service center where the product is repaired
must have safety equipment approved by local
bylaws.
• The product is examined and approved only with the
equipment given or recommended by the
manufacturer.
• Prevent health and safety risks. All personnel must
obey laws and requirements when they do the
procedures given in this manual.
• Obey the local waste regulations.
• Always make sure that all nuts and bolts are
correctly tightened.
• Use protective gloves and eye protection. Goggles
must obey the ANSI Z87.1 for US or EN166 for EU
countries.
• When using compressed air, do not point it to your
body. Air can go into the bloodstream.
• Use hearing protection when the engine is started.
• The product can make sparks and cause ignition of
flammable materials.
• Replace all damaged or missing warning symbol
decals.
• Gasoline and its fumes are poisonous.
• Gasoline can cause damage to the eyes and the
skin.
• Gasoline can cause breathing problems.
• Gasoline is flammable.
2.3 Symbols on the product
WARNING: Careless or incorrect use can
result in injury or death to the operator or
others.
Read the manual carefully and make sure
you understand the instructions before
using the product.
Always put on personal protective
equipment:
• Hearing protection
• Protective goggles or a visor
• Breathing mask.
This product in compliance with applicable
EC directives.
WARNING! Dust from cutting can cause
breathing problems. Use breathing
protection. Do not breathe exhaust fumes.
Always make sure there is good airflow.
WARNING! Sparks from the cutting blade
can cause a fire in materials such as,
gasoline, wood, fabric and dry grass.
WARNING! Kickbacks can be sudden,
fast and can cause injuries. Read and
understand the instructions in the manual
before using the product.
Make sure the cutting disc is not
damaged.
WARNING! Do not use circular saw
blades.
Note: Other symbols/decals on the product refer to
special certification requirements for some markets.
4 - Safety 651 - 001 - 27.06.2018

3 Servicing data
3.1 Symbols in the diagrams Tightening torque, Nm
651 - 001 - 27.06.2018 Servicing data - 5

3.2 Tightening torques
3-5
4-6
4-6
4-6
2,0
7-9
3-5
4-6
6 - Servicing data 651 - 001 - 27.06.2018

11-12
10-12
5-7
11-13
11-13
11-13
7-9
17-23
651 - 001 - 27.06.2018 Servicing data - 7

5-7
25-30
1-1.5
9-11
4-10
8-10
38-42
4-5
8 - Servicing data 651 - 001 - 27.06.2018

13
6-8
20-25
5
5-6
10-12
6
6
4
3
5-7
5
6-8 25-30
9-11
651 - 001 - 27.06.2018 Servicing data - 9

4 Servicing tools
4.1 Servicing tools overview
0,3 mm
1 2 3
4 5 6
7 8 9
Po-
si-
tion
Designation Used for Order No./
Source
1 Air clearance gauge To adjust the air clearance between the ignition module and the fly-
wheel.
502 51 34-02
2 Assembly punch To assemble the sealing rings of the crankshaft in the crankcase. 502 50 82-01
3 Bearing press To disassemble the primary bearing and assemble the crankshaft. 544 10 36-02
4 Bearing press To assemble the primary bearing and assemble and disassemble
blade shaft bearing and axle.
506 37 61-02
5 Bearing puller Remove the primary bearing from the crankshaft. 531 00 48-67
6 Combination wrench General. 506 38 26-01
7 Compression tester To examine the compression in the cylinder. 531 03 16-86
8 Bearing press To disassemble and assemble the clutch drum ball bearing. 504 56 79-01
9 Cylinder seal To examine the crankcase for leaks. 544 10 33-01
10 - Servicing tools 651 - 001 - 27.06.2018

4.2 Servicing tools overview
10 11 12
13 14 15
16 17 18
Po-
si-
tion
Designation Used for Order No./Source
10 Flywheel puller To disassemble the flywheel. 502 51 49-02
11 Grip plate To divide the crankcase. 544 06 00-02
12 Gudgeon pin punch To disassemble and assemble the gudgeon pin. 505 38 17-05
13 Hose catcher To catch the fuel filter in the tank. 502 50 83-01
14 Kit for piston service To do service on the piston. 502 50 70-01
15 Piston stop To disassemble the clutch. 504 91 06-05
16 Pressing device To disassemble and assemble the blade shaft bearings and axle. 575 96 20-01
17 Pressure tester To examine the carburetor, fuel lines and check valve. 501 56 27-01
18 Pressure tester To examine the crankcase for leaks. 531 03 06-23
651 - 001 - 27.06.2018 Servicing tools - 11

4.3 Servicing tools overview
19 20 21
22 23 24
25
Po-
si-
tion
Designation Used for Order No./
Source
19 Puller To disassemble the sealing rings of the crankcase in the crankcase. 504 91 40-01
20 Sealing plug To examine the crankcase for leaks. 503 55 22-01
21 Special screwdriver To adjust the idle speed. 501 60 02-03
22 Tachometer To adjust the idle and maximum speed. 502 71 14-01
23 Test spark plug To do service on the ignition unit. 502 71 13-01
24 Universal puller To disassemble the support washer of the clutch on the crankshaft.
To divide the crankcase.
504 90 90-02
25 Key Torx T27 General use. 502 71 27-02
12 - Servicing tools 651 - 001 - 27.06.2018

5 Product overview for repair and servicing
5.1 Components
1
9
19
17
16
15
8
724
23
11
10
18
13
20
22
14
2
4
5
6
21
3
12
1. Cutting blade
2. Blade guard
3. Handle for the blade guard
4. Front handle
5. Air filter cover
6. Cylinder cover
7. Starter rope handle
8. Starter
9. Combination wrench
10. Belt adjustment screw
11. Lock screws for belt adjustment
12. Rear belt guard
13. Fuel tank
14. Throttle control
15. Rear handle
16. Throttle trigger lock
17. Air purge bulb
18. Decompression valve
19. Water valve with tool holder
20. Water connector
21. Choke lever
22. Viewing glass for fuel
23. Oil guard button
24. Stop switch
651 - 001 - 27.06.2018 Product overview for repair and
servicing - 13

5.2 To disassemble into basic modules
This chapter shows how you can disassemble and
assemble the product in its basic modules.
14 - Product overview for repair and
servicing
651 - 001 - 27.06.2018

5.2.1 To remove the starter
1. Loosen the 4 screws on the guard.
2. Remove the starter.
5.2.2 To remove the cutting head
1. Loosen the nuts on the cutting head. Loosen the belt
tension with the adjuster screw.
2. Loosen the hose clip, see To disassemble the wet
system on page 60 . Loosen the nuts and remove
the front belt cover .
3. Loosen the hoses by the water valve. Remove the
belt from the pulley and remove the cutting head.
4. Remove the 2 screws on the rear belt guard.
Remove the guard.
Note: Tightening torque when you assemble: 9–11
Nm.
651 - 001 - 27.06.2018 Product overview for repair and
servicing - 15

5.2.3 To remove the air filter
1. Remove the 3 screws and remove the cover.
2. Remove the 2 screws and remove the filter holder
and the filter.
3. Remove the filter.
5.2.4 To remove the cylinder cover
1. Remove the 4 screws.
2. Push the collar of the rubber seal through the hole.
3. Remove the cylinder cover.
16 - Product overview for repair and
servicing
651 - 001 - 27.06.2018

5.2.5 To remove the carburetor
1. Remove the screw.
2. Lift the carburetor until you can access the gasoline
hose and the hose to the air purge bulb.
3. Remove the gasoline hose from the carburetor.
4. Remove the hose to the air purge bulb.
5. Remove the throttle rod from the throttle control.
5.2.6 To remove the air duct
Remove the starter, air filter cover and cylinder cover
before you remove the air duct.
1. Lift the cable for the stop switch out of its holders.
2. Remove the ignition cable at the spark plug and lift
the cable out of its holder in the cover.
651 - 001 - 27.06.2018 Product overview for repair and
servicing - 17

3. Remove the 3 screws on the air duct cover. Remove
the air duct cover.
5.2.7 To remove the muffler
Remove the cutting head the and the starter before you
remove the muffler.
1. Loosen the four screws.
2. Remove the muffler.
5.2.8 Before you remove the vibration absorbers
Before you remove the vibration absorbers you must
remove the following parts.
• Air filter
• Cylinder cover
• Top air duct cover
• The screw holding the carburetor
• Starter
• Air duct cover
• Cable lug by the ignition module
• Cable at the ground point
18 - Product overview for repair and
servicing
651 - 001 - 27.06.2018

5.2.9 To remove the vibration absorbers
1. Remove the screws of the vibration dampers.
651 - 001 - 27.06.2018 Product overview for repair and
servicing - 19

6 Repair and servicing
6.1 Starter
6.1.1 To remove the starter rope
1. To remove the spring force from the return spring,
pull out the starter rope approximately 12 in/30 cm.
Hold the starter pulley with your thumb and put the
starter rope in the notch on the starter pulley.
2. Let the starter pulley rotate slowly and wind up the
starter rope on the metal sleeve.
3. Remove the starter rope from the starter pulley.
6.1.2 To attach the new starter rope
1. Put one end of the starter rope from the top through
the hole in the starter pulley. Then pull it out through
the notch for the starter rope. Pull out most of the
starter rope but keep some to make a knot.
2. Put the other end through the cover and on through
the handle. Make two knots as in the illustration.
6.1.3 To load the return spring
1. Put the starter rope in the notch.
2. Wind the starter rope handle 4 turns around the hub.
3. Pull out the starter rope handle to make the rope
come off the hub.
4. Release the rope. Let it wind on the starter pulley.
Do it again with 3 turns of rope around the hub.
5. Extending the cord fully to make sure that the return
spring is not an end stop. It must be possible to turn
the starter pulley half a turn or more before the
spring stops the movement.
20 - Repair and servicing 651 - 001 - 27.06.2018