Husqvarna K770 Workshop Manual
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Husqvarna K770 Workshop Manual

Vac & dry cut
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Workshop manual
K770 Vac & Dry Cut
English
701 - 002 -

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Summary of Contents for Husqvarna K770

  • Page 1 Workshop manual K770 Vac & Dry Cut English 701 - 002 -...

  • Page 2: Table Of Contents

    3 Servicing data 6.14 Cutting head............60 3.1 Symbols in the diagrams........5 6.15 Gearbox............. 62 3.2 Tightening torques K770 Vac/Dry Cut....6 6.16 Fan - Dry Cut .............65 3.3 Tightening torques K770 Vac/Dry Cut....7 6.17 Dust bag - Dry Cut..........70 3.4 Tightening torques K770 Dry Cut......8 6.18 Throttle trigger and throttle lock......

  • Page 3: Introduction

    It also gives safety instructions that the personnel must obey. 1.2 Outline This manual is for K770 Vac and Dry Cut. Most chapters are applicable to the two models. The chapters that are applicable for only one model has that model name included in the title.

  • Page 4: Safety

    2 Safety 2.1 Safety definitions Always put on personal protective equipment: The definitions below give the level of severity for each • Hearing protection signal word. • Protective goggles or a visor • Breathing mask. WARNING: Injury to persons. This product in compliance with applicable EC directives.

  • Page 5: Servicing Data

    3 Servicing data 3.1 Symbols in the diagrams Tightening torque, Nm 701 - 002 - Servicing data - 5...

  • Page 6: Tightening Torques K770 Vac/Dry Cut

    3.2 Tightening torques K770 Vac/Dry Cut 6 - Servicing data 701 - 002 -...

  • Page 7: Tightening Torques K770 Vac/Dry Cut

    3.3 Tightening torques K770 Vac/Dry Cut 11-12 17-23 10-12 11-13 11-13 11-13 701 - 002 - Servicing data - 7...

  • Page 8: Tightening Torques K770 Dry Cut

    3.4 Tightening torques K770 Dry Cut 8-10 8-10 8-10 10-12 25-30 9-11 8-10 8-10 8-22 8 - Servicing data 701 - 002 -...

  • Page 9: Tightening Torques K770 Vac

    3.5 Tightening torques K770 Vac 8-10 8-10 8-10 18-22 701 - 002 - Servicing data - 9...

  • Page 10: Tightening Torques K770 Dry Cut

    3.6 Tightening torques K770 Dry Cut 10-12 25-30 9-11 10-12 10 - Servicing data 701 - 002 -...

  • Page 11: Tightening Torques K770 Vac

    3.7 Tightening torques K770 Vac 20-25 25-30 9-11 10-12 701 - 002 - Servicing data - 11...

  • Page 12: 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 13: 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 14: 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 15: Product Overview For Repair And Servicing

    5 Product overview for repair and servicing 5.1 Product overview Dry Cut 1. Cutting blade 14. Throttle trigger lock 2. Blade guard 15. Air purge bulb 3. Front handle 16. Decompression valve 4. Air filter cover 17. Fan 5. Cylinder cover 18.

  • Page 16: Product Overview Vac

    5.2 Product overview Vac 1. Cutting blade 14. Throttle trigger lock 2. Blade guard 15. Air purge bulb 3. Front handle 16. Decompression valve 4. Air filter cover 17. Bracket 5. Cylinder cover 18. Choke lever 6. Starter rope handle 19.

  • Page 17: To Disassemble Into Basic Modules

    5.3 To disassemble into basic modules This chapter shows how you can disassemble and assemble the product in its basic modules. Dry Cut 701 - 002 - Product overview for repair and servicing - 17...
  • Page 18 5.3.1 To remove the starter 3. Loosen the nuts and remove the front belt cover . 1. Loosen the 4 screws on the guard. 2. Remove the starter. 4. Remove the belt from the pulley and remove the cutting head. 5.3.2 To remove the cutting head Dry Cut 1.
  • Page 19 5.3.3 To remove the cutting head Vac 4. Remove the 2 screws on the rear belt guard. Remove the guard. 1. Loosen the nuts on the cutting head. Loosen the belt tension with the combination wrench. To loosen the belt tension, turn the nut to the 0 mark. 2.
  • Page 20 3. Loosen the 2 screws. Remove the fan. the carburetor inlet. Removal of waste is best done with a vacuum cleaner. 1. Remove the 3 screws and remove the cover. 5.3.5 To remove the air filter CAUTION: Be careful when the air filter is removed.
  • Page 21 3. Remove the air filter. 3. Remove the cylinder cover. 5.3.6 To remove the cylinder cover 1. Remove the 4 screws. 5.3.7 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.
  • Page 22 3. Remove the gasoline hose from the carburetor. 5.3.8 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. 4.
  • Page 23 5.3.9 To remove the muffler 5.3.11 To remove the vibration damping units Remove the cutting head the and the starter before you 1. Remove the screws of the vibration damping units. remove the muffler. 1. Loosen the four screws. 2. Remove the muffler. 5.3.10 Before you remove the vibration absorbers Before you remove the vibration absorbers you must...

  • Page 24: 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 starter rope from the top through 6.1.1 To remove the starter rope the hole in the starter pulley. Then pull it out through the notch for the starter rope.
  • Page 25 6.1.4 To remove the starter pulley Note: Make sure that the spacer sleeve does not fall off. To remove the starter 1. Remove the spring force. See rope on page 24 . 1. Align the starter pulley notch with the end of the spring when assembling.
  • Page 26 6.1.8 To clean the spring assembly 6.1.11 To disassemble the starter pawls Note: Do not remove the spring from the assembly. Note: The position of the washer is below the starter pawls against the flywheel. Make a note of the position of the springs in relation to the flanges on the flywheel.

  • Page 27: Ignition System

    6.1.13 To install the starter The starter pawls must come into the correct position against the starter pulley sleeve. 1. Pull out the rope approximately 0.5 m. 2. Keep this position and set the starter against the product. 3. Slowly release the rope until the starter pawls come into the correct position.
  • Page 28 6.2.4 To examine the ignition spark .02 in. 1. Ground the spark plug against the cylinder. 0.5 mm 1. Replace the spark plug with the test spark plug. See Servicing tools overview on page 14 . 2. Move the stop button to the operation position. 3.
  • Page 29 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. 1. Remove the starter and the short circuit cable on the ignition unit.
  • Page 30 6.2.8 To remove the stop switch 4. Remove the switch. 1. Remove the screw and the cable. 6.2.9 To assemble the stop switch 2. Pull the right side of the switch halfway out. 1. Push the switch halfway into position. 2.

  • Page 31: Flywheel

    6.3 Flywheel 6.3.1 To remove the flywheel Servicing Use a Husqvarna flywheel puller. Refer to tools overview on page 13 . 1. Remove the starter and lower air duct. 5. Hold the handle of the flywheel puller to lock the 2.

  • Page 32: Air Filter

    6. Attach the screw press in the center. 6.3.3 To assemble the flywheel The crankshaft and the center of the flywheel must be free from grease. Tightening torque 18–22 lbf·ft /25–30 Nm. Use a torque wrench to tighten the nut. 1.
  • Page 33 5. Replace the service filter if it is damaged. CAUTION: Make sure that the inlet pipes are not damaged and that they have a tight seal to the air filter and the carburetor. Dust in the inlet pipes is a sign of dangerous faults in the filter system.

  • Page 34: Fuel System

    6.5.1 To remove the fuel filter Servicing tools overview on page 13 . Connect the adapter to the pressure monitor with a short hose. To remove the fuel filter, use Husqvarna hose catcher. Servicing tools overview on page 13 . Refer to 1.
  • Page 35 2. This means that the fuel level in the carburetor does not get too high. 6.5.9 To examine the air purge To examine the air purge, use Husqvarna test Servicing instrument for fuel lines and check valves. See tools overview on page 13 Press the bladder of the pump.

  • Page 36: Carburetor

    6.5.10 To remove the air purge 3. Remove the carburetor from the bracket. 1. Remove the return hose and carburetor hose from the pump. 4. Pull off the hose from the carburetor and divide the units. 2. Press the click locks together with pliers and push the pump out.
  • Page 37 6.6.2 To disassemble the guides 6.6.4 To assemble the inlet manifolds 1. Remove the support insert. The parts must be installed correctly. Make a note that the guide to the inlet is irregular. 2. Push out an edge of the guides, then push them out Make a note of the groove on the holder.
  • Page 38 3. Install the support insert. 1. Pull in the manifolds past their grooves on the plate. 2. Push out the manifolds, one at a time, into their correct position. 6.6.5 Carburettor components 1. Throttle valve 3. Choke valve 2. Air valve 4.
  • Page 39 5. Fuel line 6.6.7 To remove the air valve 6. Connection to air purge It is not necessary to remove the air valve to do 7. High and low speed jet (set at the factory) servicing on the carburetor, but it makes it easier. 8.
  • Page 40 come from the venturi, can the function of the needle increase, the cause can be a damaged pump valve be examined as set out below. diaphragm. 6.6.8.4 To examine and clean the needle valve Water test on page 40 . If the Do a pressure test, refer to test shows the needle valve has a leak, remove the needle valve.
  • Page 41 examine the measurement chamber diaphragm on page 3. Clean the seating. 42 . A hole in the diaphragm stops the fuel supply. 6.6.9 To examine the pump diaphragm 1. Connect the pressure tester to the fuel pipe. 2. Put a hose from the impulse line into water. 6.6.11 To examine the check valve for the air purge bulb This valve in the carburetor stops fuel leaks out of the...
  • Page 42 6.6.13 To examine the measurement chamber 1. Put a hose on the air purge bulb connection of the diaphragm carburetor Assemble the parts in the order shown in the figure. The gaskets (1) are the same. 2. Blow in and out. The valve must close when you blow in to the carburetor and open when you blow out.
  • Page 43 opens. It also controls the quantity of fuel transmitted to 3. Clean the channels with compressed air. The rings the fuel side of the measurement chamber. show where to blow clean. 6.6.15 To examine the fuel strainer 1. Examine the strainer with a magnifying glass. 6.6.17 To examine the valve axles Leakage from the valve axles results in incorrect fuel/air mixture and dust in the engine.

  • Page 44: Decompression Valve

    6.6.18 High and low speed jets 3. Adjust the idle screw to an idle speed of approximately 2,700 rpm. The low and high speed nozzles on the carburetor have been factory set. They must not be adjusted. If the cutting blade rotates at this speed, the clutch or the friction retarder must be examined.
  • Page 45 valve closes because of the combustion pressure, as 6.7.3 To examine the decompression valve shown in figure 2. It is not necessary to start the product to examine the decompression valve. 1. Make sure that the decompression valve moves. 2. Clean the decompression valve. 3.

  • Page 46: Cylinder And Piston

    6.8 Cylinder and piston 6.8.1 To examine the compression of the cylinder The test shows leakage from the combustion chamber. 1. Run the engine warm for some minutes. 2. Close the decompression valve or put in the sealing Servicing tools overview on page 12 . plug.
  • Page 47 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. Press the needle bearing out of the connecting rod. 2.
  • Page 48 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 .006 in/0.15 mm, the piston ring groove must be measured as set out below. 6.8.5 To examine cylinder wear Examine the cylinder bore against the light.

  • Page 49: Piston Wear

    6.9 Piston wear 6.9.3 Scoring Scoring occurs when the engine is too hot. The scores The cause of engine failure can be hard to find if the are usually on the exhaust side, which is the hottest. previous operation and service of the product is not The inlet side can show equivalent damage.

  • Page 50: To Assemble The Piston

    6.10 To assemble the piston 3. Install a circlip in the piston. Lubricate new or cleaned bearings and piston rings with 2-stroke oil before you assemble them. 4. Hold the piston in position, push in the wrist pin and install the other circlip. 1.

  • Page 51: To Assemble The Cylinder

    6.11 To assemble the cylinder 4. Press down the cylinder on the piston and let the piston ring compressor move along the piston. Clean off remaining bits of the first gasket from the Tighten the screws crosswise to a torque of 10–11 surfaces that connect with the gasket.
  • Page 52 Look for cracks on the crankcase. 6.12.2 To remove the crankcase seal To replace the crankcase seal rings, use a Husqvarna Servicing tools puller and an assembly punch. See overview on page 14 and Servicing tools overview on page 12 .
  • Page 53 Divide the crankcase with a universal puller and a grip Servicing tools overview the clutch drum. plate from Husqvarna. Refer to on page 14 and Servicing tools overview on page 13 . 1. Disassemble the basic modules from the crankcase.
  • Page 54 If not, you can remove the bearing with the puller. See Servicing tools overview on page 12 . To change the bearing you must use two Husqvarna 2. Attach the puller unit and press the bearing off from the crankshaft.
  • Page 55 Use a hot air gun around the Servicing tools Use a Husqvarna bearing press (refer to bearing, max. 300 °F/150 °C. Put the sleeve from overview on page 12 ) to assemble the bearings in the 2 the tool kit against the bearing and hit it with a large crankcase halves.
  • Page 56 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 57: 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 13 . Before stop. See you remove the clutch you must remove the cutting...
  • Page 58 assembly. Do not replace one shoe from a different 6.13.4 To remove the clutch springs clutch as this causes bad balance. 1. Put a large screwdriver in each spring end. 2. Expand the spring using circlip pliers and remove the spring. The inner diameter of the clutch drum must not be more than 79.8 mm.
  • Page 59 6.13.7 Belt pulley bearings 3. Pull out the bearing by tightening the nut. The clutch drum and belt pulley are connected units. The belt pulley has two permanently lubricated ball bearings that are adjacent to each other without spacers. The outer rings of the ball bearings are installed with a light force on the belt pulley.

  • Page 60: Cutting Head

    Note: When you install the clutch, you must first put the Note: The illustration shows the screwdriver and the washer on the crankshaft. wrench from below. 4. Remove the pulley. 6.14 Cutting head 6.14.1 To disassemble the blade guard 1. Remove the cutting blade from the blade guard. 5.
  • Page 61 6. Remove the blade guard extender and dust shield. 8. Remove the screw that hold the dust shiel. 7. Remove the spring from the metal side of the blade guard extender. 701 - 002 - Repair and servicing - 61...

  • Page 62: Gearbox

    6.15 Gearbox 3. Remove the gears. 6.15.1 To remove the gears 1. Loosen the 4 screws. 2. Remove the gearbox lid and the gasket. You can Note: Do not remove the gears from their shafts. use a mandrel in the 2 holes in the blade guard. They are supplied as a kit.
  • Page 63 6.15.2 To remove the bearings 6.15.3 To install bearings 1 & 2 1. Remove the bearings with a counter stay device or a To install the bearings, use a press and Husqvarna Servicing tools overview on page slide hammer and internal bearing extractors. See bearing press.
  • Page 64 6.15.4.2 To use a press 6.15.5 To install the gears 1. Use the large support from the tool kit to press the 1. Install the gears. bearing. For support on the other side, use a piece of a rod with diameter 40 - 44mm. 2.

  • Page 65: Fan - Dry Cut

    6.16 Fan - Dry Cut 6.15.6 To apply grease to the gearbox 1. Remove the 2 screws. 6.16.1 To disassemble the fan To remove 1. Remove the fan from the product. See the fan Dry Cut on page 19 2. Put the combination wrench or a 13mm socket in a vise and loosen the nut.
  • Page 66 6.16.2 To remove the fan bearings • To remove the bearings you can use a Husqvarna bearing press for the fan bearings. Refer to Servicing tools overview on page 12 . You can also use a standard press.
  • Page 67 2. Use a mandrel of maximum diameter of 20mm. 6.16.3 To install the fan bearings To install the bearings you can use a Husqvarna bearing Servicing tools press for the fan bearings. Refer to 701 - 002 -...
  • Page 68 4. Assemble the tool kit. Make sure that the sleeve in press. the bearing set is turned as in the picture. 6.16.3.1 With a Husqvarna bearing press 1. Put an extension and a 13mm socket in a vise. 2. Apply some drops of oil to the threads on the screw.
  • Page 69 6. Tighten the nut until the bearing is fully put into the 9. Make sure that the seal is level before you tighten housing. the nut. 7. Do steps 3 to 6 with the second bearing. 8. Before you install the seal, apply grease on top of the bearing.

  • Page 70: Dust Bag - Dry Cut

    6.16.3.2 With a regular press 4. Before you put the seal, apply grease on top of the Servicing tools overview on page 14 . bearing. See 1. Use a pipe as support. Minimum inner diameter: 34mm. Maximum outer diameter: 56mm 2.
  • Page 71 6.17.2 To disassemble the dust bag 4. Hold and shake the dust bag until it is empty. WARNING: Remove dust from the dust bag that can be used again. 1. Loosen the rope and remove the hose from the dust bag.

  • Page 72: Throttle Trigger And Throttle Lock

    3. Put the hose into the check valve and tighten the To remove the 1. Remove the carburetor. See rope. carburetor on page 21 . 2. Push in the lower part of the throttle lock with a v-jaw tongue-and-groove pliers. 6.17.5 To discard the dust bag Note: Applicable only for dust bags that are discarded when they are full.

  • Page 73: Oilguard - Dry Cut

    The OilGuard prevents the product from running with incorrect fuel. For the OilGuard to operate, an oil containing dye, “Husqvarna OilGuard oil”, must be added. Fuel analysis starts 10 seconds after startup and continues for 50 seconds. If the OilGuard identifies incorrect fuel, the engine speed limit is 3800 rpm.
  • Page 74 6.19.2 To examine the power supply for the OilGuard 1. Remove the filter and cylinder cover. 2. Connect a multimeter to a ground point and the point of measure. Measure at idle rpm. The voltage must be 20–40 V AC. 74 - Repair and servicing 701 - 002 -...

  • Page 75: 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 76: Engine Stops During Operation - No Sparks

    7.2 Engine stops during operation - no sparks There are no sparks at the spark plug Symptom/Category 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 The switch cable or high-voltage cable is Replace...

  • Page 77: 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 crack or pin hole Air has gone through the pulse pipe...

  • Page 78: Dust

    7.6 Dust Dry Cut There is too much dust Symptom Cause Solution Too much dust goes out in the air The fan is broken or worn out Repair or replace the fan during operation. The check valve is not installed cor- Install the check valve correctly rectly The hose is loose...

  • Page 79: Wiring Diagram - Dry Cut

    8 Wiring diagram - Dry Cut 8.1 Wiring diagram OilGuard 1. OilGuard - OilGuard plug - ignition module 2. OilGuard - stop switch - ignition module 3. OilGuard - stop switch - ground 701 - 002 - Wiring diagram - Dry Cut - 79...
  • Page 80 2019-01-17...

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