Husqvarna K770 SmartGuard Workshop Manual
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Husqvarna K770 SmartGuard Workshop Manual

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Workshop manual
K770 SmartGuard
English
1453 - 001 - 02.04.2020

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Summary of Contents for Husqvarna K770 SmartGuard

  • Page 1 Workshop manual K770 SmartGuard English 1453 - 001 - 02.04.2020...

  • Page 2: Table Of Contents

    Contents 1 Introduction 7 Troubleshooting 1.1 Document description..........3 7.1 Engine does not start........... 70 1.2 Target group............3 7.2 Engine stops during operation - no sparks...71 1.3 Revisions..............3 7.3 Engine stops during operation......71 1.4 Safety..............3 7.4 Weak output or change of speed......72 1.5 Servicing tools............3 7.5 Other engine problems.........72 2 Safety...

  • Page 3: Introduction

    1.5 Servicing tools The manual gives information about necessary servicing tools. Always use original tools from Husqvarna. 1453 - 001 - 02.04.2020 Introduction - 3...

  • Page 4: Safety

    2 Safety 2.1 Safety definitions Use approved protective helmet, hearing protection, eye protection and respiratory The definitions below give the level of severity for each protection. signal word. This product complies with applicable EC WARNING: Injury to persons. Directives. Dust forms when cutting. The dust can CAUTION: Damage to the product.

  • Page 5: Servicing Data

    3 Servicing data 3.1 Symbols in the diagrams Tightening torque, Nm 1453 - 001 - 02.04.2020 Servicing data - 5...

  • Page 6: Tightening Torques

    3.2 Tightening torques 6 - Servicing data 1453 - 001 - 02.04.2020...
  • Page 7 11-12 17-23 10-12 11-13 11-13 11-13 1453 - 001 - 02.04.2020 Servicing data - 7...
  • Page 8 25-30 9-11 1-1.5 1-1.5 38-42 8-10 14-16 0.5-0.8 14-16 4-10 8 - Servicing data 1453 - 001 - 02.04.2020...
  • Page 9 20-25 25-30 9-11 10-12 1453 - 001 - 02.04.2020 Servicing data - 9...

  • Page 10: Servicing Tools

    4 Servicing tools 4.1 Servicing tools overview Designation Used for Order No./ Source tion Air clearance gauge To adjust the air clearance between the ignition module and the fly- 502 51 34-02 wheel. Assembly punch To assemble the sealing rings of the crankshaft in the crankcase. 502 50 82-01 Bearing press To disassemble the primary bearing and assemble the crankshaft.

  • Page 11: Servicing Tools Overview

    4.2 Servicing tools overview Designation Used for Order No./Source tion Flywheel puller To disassemble the flywheel. 502 51 49-02 Grip plate To divide the crankcase. 544 06 00-02 Gudgeon pin punch To disassemble and assemble the gudgeon pin. 505 38 17-05 Hose catcher To catch the fuel filter in the tank.

  • Page 12: Servicing Tools Overview

    4.3 Servicing tools overview Designation Used for Order No./ Source tion Puller To disassemble the sealing rings of the crankcase in the crankcase. 504 91 40-01 Sealing plug To examine the crankcase for leaks. 503 55 22-01 Special screwdriver To adjust the idle speed. 501 60 02-03 Tachometer To adjust the idle and maximum speed.

  • Page 13: Product Overview For Repair And Servicing

    5 Product overview for repair and servicing 5.1 Components 1453 - 001 - 02.04.2020 Product overview for repair and servicing - 13...

  • Page 14: Basic Modules Of The Product

    17. Decompression valve 2. Adjustment handle for blade guard 18. Belt adjustment screw 3. Water hose 19. Air purge bulb 4. Water valve 20. Fuel tank cap 5. Air filter cover 21. Water connection with filter 6. Rear handle 22. Sight glass for fuel 7.
  • Page 15 5.2.1 To remove the starter 5.2.2 To remove the cutting head To disassemble the 1. Loosen the 4 screws on the guard. 1. Loosen the hose clip. Refer to wet system on page 66 . Loosen the 3 nuts on the 2.
  • Page 16 3. Remove the front belt guard. 5. Remove the 2 screws on the rear belt guard. Remove the rear belt guard. 4. Remove the cutting head. 16 - Product overview for repair 1453 - 001 - 02.04.2020 and servicing...
  • Page 17 5.2.3 To remove the air filter 3. Remove the air filter. 1. Remove the 3 screws and remove the air filter cover. 2. Remove the 2 screws and remove the air filter holder and the air filter. 1453 - 001 - 02.04.2020 Product overview for repair and servicing - 17...
  • Page 18 5.2.4 To remove the cylinder cover 3. Remove the cylinder cover. 1. Remove the 4 screws. 2. Push the collar of the rubber seal through the hole. 18 - Product overview for repair 1453 - 001 - 02.04.2020 and servicing...
  • Page 19 5.2.5 To remove the carburetor 4. Remove the hose to the air purge bulb. 1. Remove the screw. 5. Remove the throttle rod from the throttle control. 2. Lift the carburetor until you can get access to the fuel hose and the hose to the air purge bulb. 3.
  • Page 20 5.2.6 To remove the air duct 5.2.7 To remove the muffler Remove the starter, air filter cover and cylinder cover Remove the cutting head the and the starter before you before you remove the air duct. remove the muffler. 1. Lift the cable for the stop switch out of its holders. 1.
  • Page 21 6. Remove the screws of the vibration damping units. 1453 - 001 - 02.04.2020 Product overview for repair and servicing - 21...

  • Page 22: Repair And Servicing

    6 Repair and servicing 6.1 Starter 6.1.2 To attach the new starter rope 1. Put one end of the new starter rope from the top 6.1.1 To remove the starter rope through the hole in the starter pulley. Then pull it out through the notch for the starter rope.
  • Page 23 6.1.4 To remove the starter pulley 6.1.6 To install the starter pulley 1. Decrease the tension in the return spring. Refer to Note: Make sure that the spacer sleeve does not fall off. remove the starter rope on page 22 . •...
  • Page 24 6.1.8 To clean the spring assembly 6.1.11 To disassemble the starter pawls Note: Do not remove the spring from the spring Note: The position of the washer is below the starter assembly. pawls against the flywheel. Make a note of the position of the springs in relation to the flanges on the flywheel.

  • Page 25: Ignition System

    6.1.13 To install the starter transformer. The secondary coil increases the voltage to 20 000V. This causes a spark. Note: The starter pawls must come into the correct position against the starter pulley sleeve. 1. Pull out the starter rope approximately 0.5 m. 2.
  • Page 26 6.2.4 To examine the ignition spark .02 in. 1. Ground the spark plug to the cylinder. 0.5 mm 1. Replace the spark plug with the test spark plug. Servicing tools overview on page 12 . Refer to 2. Move the stop switch to the operation position. 3.
  • Page 27 6.2.6 To examine the ignition cable 6.2.7 To examine the short circuit cable and the stop switch 1. Pull up the rubber seal by the ignition unit and remove the ignition cable. To remove the starter 1. Remove the starter. Refer to on page 15 .
  • Page 28 6.2.8 To remove the stop switch 4. Remove the stop switch. 1. Remove the screw and disconnect the cable. 6.2.9 To install the stop switch 2. Pull the right side of the switch approximately 10 1. Push the stop switch into position (A). 2.

  • Page 29: Flywheel

    10–12 Nm. 6.3 Flywheel 6.3.1 To remove the flywheel Servicing Use a Husqvarna flywheel puller. Refer to tools overview on page 11 . To remove the starter 1. Remove the starter. Refer to on page 15 .

  • Page 30: Air Filter

    7. Attach the screw press in the center. 6.3.3 To install the flywheel The crankshaft and the center of the flywheel must be free from grease. Tightening torque 25 – 30 Nm. Use a torque wrench to tighten the nut. 1.

  • Page 31: Fuel System

    They must be repaired before the product is operated. 6.5 Fuel system 6.5.1 To remove the fuel filter To remove the fuel filter, use Husqvarna hose catcher. Servicing tools overview on page 11 . Refer to The service filter prevents dirt in the engine. The service 1.
  • Page 32 6.5.3 To examine the fuel system for leakages 6.5.5 Function of the tank venting 1. Connect the adapter to a pressure test tool. Refer to The fuel tank has a check valve that lets air enter the Servicing tools overview on page 11 . tank, but prevents fuel leakage.

  • Page 33: Carburetor

    (B). This means that the fuel level in the carburetor does not become too high. 6.5.9 To do a test of the air purge bulb A Husqvarna test instrument for fuel lines and check Servicing tools overview valves is necessary. Refer to...
  • Page 34 3. Remove the carburetor from the bracket. 6.6.2 To disassemble the guides 1. Remove the support insert. 4. Pull off the hose from the carburetor and divide the units. 2. Push out an edge of the guides, then push them out by hand.
  • Page 35 6.6.4 To assemble the inlet manifolds 1. Pull in the manifolds past their grooves on the plate. Make a note that the guide to the inlet is irregular. 2. Push out the manifolds, one at a time, into their Make a note of the groove on the holder. correct position.
  • Page 36 6.6.5 Carburetor components 1. Throttle valve connection as short as possible, this gives a more accurate test result. 2. Air valve 3. Choke valve 4. Impulse channel, from the crankcase to the carburetor pump diaphragm 5. Fuel line from the fuel tank 6.
  • Page 37 6.6.7 To remove the air valve come from the venturi, can the function of the needle valve be examined as set out below. It is not necessary to remove the air valve to do servicing on the carburetor, but it makes it easier. 1.
  • Page 38 increase, the cause can be a damaged pump 4. Clean the needle valve seating. diaphragm. 5. Install the needle valve in the opposite sequence. 6.6.8.4 To examine and clean the needle valve 6.6.9 To examine the pump diaphragm 1. Remove the needle valve. 1.
  • Page 39 chamber diaphragm on page 39 . A hole in the 6.6.10 To examine the check valve for the air purge diaphragm stops the fuel supply. bulb This valve in the carburetor stops fuel leaks out of the carburetor if leaks occur in the air purge bulb or connections.
  • Page 40 6.6.14 To examine the fuel strainer • Examine the diaphragm visually. Fuel on the top 1. Examine the fuel strainer with a magnifying glass. side, to the cover, is a sign of leaks. If there is fuel on the top side, replace the diaphragm. 2.
  • Page 41 6.6.16 To examine the valve axles WARNING: Adjust the idle speed outdoors. The exhaust fumes are poisonous. Leakage from the valve axles results in incorrect fuel/air mixture and dust in the engine. 1. Make sure there is no radial play on the valve axles. 1.

  • Page 42: Decompression Valve

    6.6.19 To assemble the air valve 6.7.2 To disassemble the decompression valve • Attach the air valve to the carburetor with 2 screws. • Remove the decompression valve with a long socket or the combination wrench. 6.7.3 To examine the decompression valve 1.

  • Page 43: Cylinder And Piston

    vibration damping units on page 20 . Tighten the engine 6.7.4 To install the decompression valve body in a vise. Use soft guards. 1. Clean and examine the sealing washer before you install the decompression valve. 1. Remove the 4 screws and remove the cylinder. 6.8 Cylinder and piston 6.8.1 To examine the compression of the cylinder The test shows leakage from the combustion chamber.
  • Page 44 4. Push out the wrist pin by hand. If it is tight, use a CAUTION: Do not use the piston stop on this small hammer and light force. product. 1. Put the support plate below the piston. 5. Push the needle bearing out of the connecting rod. 2.
  • Page 45 examined carefully. It is important to identify the cause 6.8.7 Piston wear tolerances of the unusual wear. 6.8.7.1 Piston ring play If the piston ring play is more than 0.006 in./0.15 mm, the piston ring groove must be measured as set out below.

  • Page 46: Piston Wear

    6.9 Piston wear Examine the product to see if it has broken down because of an incorrect oil mixture, or no oil at all. If The cause of engine failure can be hard to find if the there is oil on a piston that is too hot it can carbonize. If previous operation and service of the product is not not, check if the connecting rod or the crankcase has a available.

  • Page 47: To Assemble The Piston

    6.10 To assemble the piston 3. Seal with a cloth or paper to make sure that parts do not fall into the crankcase. Lubricate new or cleaned bearings and piston rings with 2-stroke oil before you assemble them. 4. Install a snap ring in the piston. 1.

  • Page 48: To Assemble The Cylinder

    6.11 To assemble the cylinder 5. Push down the cylinder on the piston and let the piston ring compressor move along the piston. 1. Clean and remove remaining bits of the first gasket Tighten the screws crosswise to a torque of 14–15 from the surfaces that connect with the gasket.
  • Page 49 4. At the inlet port, loosen the 2 screws at the lower part of the carburetor. 6.12.2 To remove the crankcase seal To replace the crankcase seal rings, use a Husqvarna Servicing tools puller and an assembly punch. Refer to overview on page 12 and Servicing tools overview on page 10 .
  • Page 50 Divide the crankcase with a universal puller and a grip Servicing tools overview the clutch drum (A). plate from Husqvarna. Refer to on page 12 and Servicing tools overview on page 11 . 1. Disassemble the basic modules from the crankcase.
  • Page 51 Servicing 5. Make sure there is no radial play on the connecting use 2 Husqvarna bearing press kits. Refer to tools overview on page 10 . rod by the crankshaft journal. If there is radial play, the unit must be replaced.
  • Page 52 3. Put the crankcase halves against a flat piece of 6.12.7 To install the crankcase bearings wood or equivalent. Use a hot air gun around the Use a Husqvarna bearing press to assemble the bearing, max. 300 °F/150 °C. Servicing bearings in the 2 crankcase halves.
  • Page 53 3. Put the sleeve from the tool kit against the 6. Install the new crankcase gasket. crankcase half. Tighten the mandrel on the crankshaft by hand. 7. Assemble the other crankcase half using the same Note: The crankshaft has a reverse thread on the procedure.

  • Page 54: Clutch

    1 mm. Replace if necessary with a complete clutch 6.13 Clutch 6.13.1 To remove the clutch To remove the clutch you must use a Husqvarna piston Servicing tools overview on page 11 . stop. Refer to Before you remove the clutch you must remove the 54 - Repair and servicing 1453 - 001 - 02.04.2020...
  • Page 55 assembly. Do not replace one shoe from a different 6.13.4 To remove and install the clutch springs clutch as this causes bad balance. 1. Put a large screwdriver in each spring end. 2. Expand the spring with circlip pliers and remove the spring.
  • Page 56 kit also contains the screw (D) with washers and nut. 6.13.8 To install the belt pulley bearings Lubricate the threads of the screw and the washers. 1. Put the support plate of the bearings in a vise. Put the 2 ball bearings on the support plate. 1.

  • Page 57: Cutting Head

    6.14 Cutting head 3. Remove the 4 screws and the bushings. Discard the screws. 6.14.1 To disassemble and assemble the SmartGuard 1. Remove the springs from the front arms. 4. Remove the SmartGuard. 2. Remove the plastic covers and the springs. Discard the 4 screws.
  • Page 58 5. Remove the 2 screws and remove the plates. 7. Remove the arms. Discard the screws. 6. Remove the 4 screws and the 2 wheels. Discard the 8. Remove the springs from the handle. screws. 58 - Repair and servicing 1453 - 001 - 02.04.2020...
  • Page 59 9. Remove the handle. CAUTION: Apply grease on the bushings. Refer to Servicing tools overview on page 12 . 10. Remove the spring. 11. Assemble the SmartGuard in opposite sequence. CAUTION: Discard and replace all self locking screws each time they are removed. 1453 - 001 - 02.04.2020 Repair and servicing - 59...
  • Page 60 6.14.2 To disassemble the blade guard and the 4. Lock the belt pulley with a mandrel or a screwdriver and loosen the center screw. bearing housing 1. Remove the cutting head from the product. Refer to To remove the cutting head on page 15 . 2.
  • Page 61 6. Remove the 3 screws and the retarder. brake shoes (D) are pressed against the brake drum (C) by the spring (A). These units are held in position by the guide plate (B). When the speed goes above work speed, the brake shoes are pushed out from the brake drum.
  • Page 62 6.14.6 To assemble the retarder unit 6.14.7 To assemble the retarder and belt pulley 1. Put the spring (A) in position in the guide plate (B). 1. Assemble the plate of the retarder unit and the belt Note where the spring ends must be. pulley with the 4 screws.
  • Page 63 • If you replace the bearings with a bearing press kit, housing. use the Husqvarna bearing press kit. Refer to Servicing tools overview on page 10 . 1. Turn the support for assemble (A) with its shoulder up and put the bearing housing on top of it.
  • Page 64 Put the blade shaft bearing on the bearing puller. housing and put the medium sized mandrel (A) from the Husqvarna press tool kit on top of the blade shaft bearing. 6.14.9 To assemble the blade shaft bearing c) Push down the blade shaft bearing fully to the CAUTION: Do not put force between the inner stop in the bearing housing..

  • Page 65: Wet System

    3. Use a plastic hammer and push the axle down until 6. Put the axle with the blade shaft bearing in the the spacer touches the inner stop in the bearing bearing housing with the spacer down. housing. 7. Use a plastic hammer and push down the axle. 4.
  • Page 66 made for different types of machines and uses. Find the 6.15.2 To disassemble the wet system correct nozzle in the spare parts list. 1. Remove the screws that hold the spray nozzle. 2. Remove the filter with a wood screw. 3.

  • Page 67: Throttle Trigger And Throttle Trigger Lockout

    6.16 Throttle trigger and throttle trigger lockout 6.15.3 To assemble the wet system 1. Put the spray nozzles on to the blade guard. 6.16.1 To remove the throttle trigger and throttle trigger lockout When you remove the throttle trigger lockout, use a V- jaw adjustable pliers.

  • Page 68: Oilguard

    For the OilGuard to operate, an oil until the throttle trigger lockout is pressed. containing dye, Husqvarna OilGuard oil, must be added. Fuel analysis starts 10 seconds after startup and 6.16.3 To assemble the throttle trigger and throttle continues for 50 seconds.
  • Page 69 The blue plug above the stop button closes the circuit to OilGuard (E in the illustration above). To override the OilGuard function, remove the blue plug (A) with a screwdriver and replace it with an orange plastic plug (B). 6.17.2 To examine the power supply for the OilGuard 1.

  • Page 70: Troubleshooting

    7 Troubleshooting 7.1 Engine does not start Remove the spark plug from the cylinder. Hold the cylinder, pull the starter rope and see if there are sparks between the spark plug electrodes. There are no sparks at the spark plug. Examine Cause Solution...

  • Page 71: Engine Stops During Operation - No Sparks

    7.2 Engine stops during operation - no sparks There are no sparks at the spark plug Problem Cause Solution Engine suddenly The switch is accidentally set to off. Set the switch to the left position. stops. The plug cap is not attached. Attach the plug cap fully.

  • Page 72: Weak Output Or Change Of Speed

    7.4 Weak output or change of speed There are no sparks at the spark plug Symptom/Category Cause Solution Compression is good Air has gone through the fuel pipe joint. Make sure it is tight. and there is no flame Air has gone into the fuel pipe because of a Replace.

  • Page 73: Wiring Diagram

    8 Wiring diagram 8.1 Wiring diagram OilGuard 1. OilGuard - OilGuard plug - ignition module 2. OilGuard - stop switch - ignition module 3. OilGuard - stop switch - ground 1453 - 001 - 02.04.2020 Wiring diagram - 73...
  • Page 74 74 - Wiring diagram 1453 - 001 - 02.04.2020...
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