Husqvarna K770 SmartGuard Workshop Manual Download

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Workshop manual

K770 SmartGuard

English

1453 - 001 - 02.04.2020

Summary of Contents for K770 SmartGuard

Page 1: ...Workshop manual K770 SmartGuard English 1453 001 02 04 2020 ...

Page 2: ... product 14 6 Repair and servicing 6 1 Starter 22 6 2 Ignition system 25 6 3 Flywheel 29 6 4 Air filter 30 6 5 Fuel system 31 6 6 Carburetor 33 6 7 Decompression valve 42 6 8 Cylinder and piston 43 6 9 Piston wear 46 6 10 To assemble the piston 47 6 11 To assemble the cylinder 48 6 12 Crankcase 48 6 13 Clutch 54 6 14 Cutting head 57 6 15 Wet system 65 6 16 Throttle trigger and throttle trigger loc...

Page 3: ...tand 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...

Page 4: ...ssing 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 This product can be dangerous and cause serious injury or death to the operator or others Be careful and use the product correctly Read the operator s manual carefully and make sure that yo...

Page 5: ...3 Servicing data 3 1 Symbols in the diagrams Tightening torque Nm 1453 001 02 04 2020 Servicing data 5 ...

Page 6: ...3 2 Tightening torques 3 5 4 6 4 6 4 6 2 0 7 9 3 5 4 6 6 Servicing data 1453 001 02 04 2020 ...

Page 7: ...11 12 10 12 5 7 11 13 11 13 11 13 7 9 17 23 1453 001 02 04 2020 Servicing data 7 ...

Page 8: ...25 30 1 1 5 9 11 1 1 5 38 42 14 16 4 10 6 8 6 8 14 16 0 5 0 8 4 6 5 7 8 10 8 Servicing data 1453 001 02 04 2020 ...

Page 9: ...13 6 8 20 25 5 5 6 10 12 6 6 4 3 5 7 5 6 8 25 30 9 11 1453 001 02 04 2020 Servicing data 9 ...

Page 10: ...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 disassemb...

Page 11: ...05 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 ...

Page 12: ...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 servicing 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 26 Grease To apply on the bushings of t...

Page 13: ...5 Product overview for repair and servicing 5 1 Components 10 1 2 3 4 9 8 7 5 24 23 27 25 26 12 15 11 14 13 16 17 18 19 20 21 6 22 1453 001 02 04 2020 Product overview for repair and servicing 13 ...

Page 14: ...Lock screws for belt adjustment 17 Decompression valve 18 Belt adjustment screw 19 Air purge bulb 20 Fuel tank cap 21 Water connection with filter 22 Sight glass for fuel 23 OilGuard button 24 Choke lever 25 Throttle trigger lockout 26 Throttle control 27 Stop switch 5 2 Basic modules of the product This chapter shows how you can disassemble and assemble the product in its basic modules 14 Product...

Page 15: ...the starter 5 2 2 To remove the cutting head 1 Loosen the hose clip Refer to To disassemble the wet system on page 66 Loosen the 3 nuts on the front belt guard 2 Loosen the belt tension with the adjuster screw 1453 001 02 04 2020 Product overview for repair and servicing 15 ...

Page 16: ...3 Remove the front belt guard 4 Remove the cutting head 5 Remove the 2 screws on the rear belt guard Remove the rear belt guard 16 Product overview for repair and servicing 1453 001 02 04 2020 ...

Page 17: ... 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 3 Remove the air filter 1453 001 02 04 2020 Product overview for repair and servicing 17 ...

Page 18: ... 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 18 Product overview for repair and servicing 1453 001 02 04 2020 ...

Page 19: ...ntil you can get access to the fuel hose and the hose to the air purge bulb 3 Remove the fuel hose from the carburetor 4 Remove the hose to the air purge bulb 5 Remove the throttle rod from the throttle control 1453 001 02 04 2020 Product overview for repair and servicing 19 ...

Page 20: ...move the muffler 1 Loosen the 4 screws 2 Remove the muffler 5 2 8 To remove the vibration damping units 1 Remove the air filter and cylinder cover Refer to To remove the air filter on page 17 2 Remove the air duct cover Refer to To remove the air duct on page 20 3 Remove the screw that holds the carburetor Refer to To remove the carburetor on page 19 4 Remove the cable lug by the ignition module R...

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: ... 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 2 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 4 turns around the hub 3 Pull out the starter rope handle to make the starter rope come off the hu...

Page 23: ... the grease seal against the spring assembly 6 1 6 To install the starter pulley Note Make sure that the spacer sleeve does not fall off Align the starter pulley notch with the end of the spring during assembly Put the center bolt into the starter pulley assembly 6 1 7 To remove the spring assembly WARNING Always use eye protection when you disassemble the spring assembly There is a risk for eye i...

Page 24: ...ectly and the starter pawls move freely 2 If it is necessary disassemble and clean the starter pawls 6 1 11 To disassemble the starter pawls 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 1 Remove the shoulder screws 6 1 12 To assemble the starter pawls Note The spring must not ge...

Page 25: ...e sequence is in the diagram in the illustration The dotted line shows the voltage if the current is not broken Current moves through the coil by the permanent magnet on the flywheel The electronic digital unit senses the voltage in the primary coil It breaks the current before the piston is at the high turning point Until this point the primary coil is in a closed circuit With an open circuit the...

Page 26: ...f dirt and oil Clean with a wire brush Note An electrode with soft edges and damaged ceramic around it can cause pre ignition You must replace a spark plug with soft edges 02 in 0 5 mm 1 Replace the spark plug with the test spark plug Refer to Servicing tools overview on page 12 2 Move the stop button to the run position 3 Ground the test spark plug 4 Pull the starter rope handle as if you start t...

Page 27: ... this test examine the short circuit cable 6 2 7 To examine the short circuit cable and the stop switch 1 Remove the starter Refer to To remove the starter on page 15 2 Remove the short circuit cable on the ignition unit 3 Put back the starter and make sure that the spark plug makes a spark 4 Examine the short circuit cable a Use a battery in series with a test lamp or a multimeter b Connect to th...

Page 28: ...ch on the left side with a screwdriver and pull the right side out 4 Remove the stop switch 6 2 9 To install the stop switch 1 Push the stop switch into position A 2 Push in the left side until it locks B 3 Push in the right side C A B C 4 Connect the cables to the stop switch D 5 Tighten the screw E D D E 28 Repair and servicing 1453 001 02 04 2020 ...

Page 29: ...ywheel Use a Husqvarna flywheel puller Refer to Servicing tools overview on page 11 1 Remove the starter Refer to To remove the starter on page 15 2 Remove the lower air duct Refer to To remove the air duct on page 20 3 Loosen the springs and put the starter pawls in their outer positions 4 Put a 13 mm socket on the center screw of the flywheel 5 Attach the flywheel puller on the socket with the s...

Page 30: ...n the key in the flywheel with the keyway on the crankshaft Install the washer and nut 2 Remove the tool and put the springs on the starter pawls 6 4 Air filter 6 4 1 Function of the air filter The centrifugal cleaning is the first step in the process to clean the inlet air The blades on the flywheel supply the cylinder with cool air This is shown in the illustration The blades are also the part i...

Page 31: ... are not damaged and that it has a tight seal to the filter and the carburetor Dust in the inlet pipes is a sign of dangerous faults in the filter 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 Refer to Servicing tools overview on page 11 1 Remove the fuel tank cap 2 Catch the fuel hos...

Page 32: ...same time pull it out from the hole for the fuel tank cap 6 5 5 Function of the tank venting The fuel tank has a check valve that lets air enter the tank but prevents fuel leakage The filter lets air through slowly 6 5 6 Tank air flow fault indication If the tank air flow is blocked and the engine operates the tank will have low pressure This decreases fuel supply and the power When you open the f...

Page 33: ...the test instrument to the hose from the air purge bulb 2 Set the test instrument for vacuum test 3 Push the air purge bulb to increase the pressure to 0 3 0 5 bar If the pressure can be increased to 0 3 0 5 bar the air purge bulb and hose connection are not damaged Then it is necessary to look for faults in the other components of the fuel system 6 5 10 To remove the air purge bulb 1 Remove the r...

Page 34: ...upport insert 2 Push out an edge of the guides then push them out by hand 6 6 3 To examine the inlet system Dust can decrease the life of the engine Dust on the inner side of the seals means there are defective or incorrectly installed components Look for leaks Make sure the rubber guides are not cracked 34 Repair and servicing 1453 001 02 04 2020 ...

Page 35: ...de to the inlet is irregular Make a note of the groove on the holder 1 Pull in the manifolds past their grooves on the plate 2 Push out the manifolds one at a time into their correct position 3 Install the support insert 1453 001 02 04 2020 Repair and servicing 35 ...

Page 36: ...speed adjustment 9 Throttle lever for choke 10 SmartCarb 11 Fuel pump diaphragm 12 Fuel pump valves 13 Fuel chamber measurement chamber diaphragm above 14 Needle valve 6 6 6 Pressure tester The pump piston of the pressure tester must be operated with one hand Refer to Servicing tools overview on page 11 The pressure tester is supplied with an adapter for small dimensions Make the hose connection a...

Page 37: ...me The result will not be accurate When the carburetor is full turn the carburetor with the pulse line up as shown in the picture Increase the pressure to approximately 30 psi 2 bar Let the fuel go out through the venturi which is fully in water Not until air bubbles come from the venturi can the function of the needle valve be examined as set out below 6 6 8 3 To examine external leakage and the ...

Page 38: ... there are signs of particles or if the end of the needle valve is damaged replace the needle valve 4 Clean the needle valve seating 5 Install the needle valve in the opposite sequence 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 3 Apply pressure with the tester If air comes out of the impulse channel the pump diap...

Page 39: ...carburetor body The air chamber and the fuel chamber are divided by the measurement chamber diaphragm The diaphragm controls and keeps a constant level of fuel in the fuel chamber through the mechanically connected needle valve The air chamber is near the inlet after the air filters and gives the air chamber the same pressure You cannot examine the chamber diaphragm with a pressure check To examin...

Page 40: ... valve opens It also controls the quantity of fuel transmitted to the fuel side of the measurement chamber B A B 6 6 14 To examine the fuel strainer 1 Examine the fuel strainer with a magnifying glass 2 Remove loose dirt particles from the seating of the needle valve with air Replace the fuel strainer if it is damaged Remove the fuel strainer with a needle and install with a 7 mm pin punch 6 6 15 ...

Page 41: ...s overview on page 12 Make sure that the cutting blade is installed Note Do not connect the tachometer directly to the ignition system The tachometer senses the magnetic field from the ignition system Note Do not remove the air filter cover WARNING Adjust the idle speed outdoors The exhaust fumes are poisonous 1 Operate the product for approximately 5 minutes until it is warm 2 Keep the instrument...

Page 42: ... To disassemble the decompression valve Remove the decompression valve with a long socket or the combination wrench 6 7 3 To examine the decompression valve 1 Make sure that the decompression valve moves 2 Clean the decompression valve 3 Apply leakage spray or soap water on the decompression valve before installation 4 Install the decompression valve Refer to To install the decompression valve on ...

Page 43: ...Make a note of the average of the tests The average for a new engine is approximately 10 bar 150 psi Values less than 8 bar 120 psi show faults with or on the cylinder piston or piston rings 6 8 2 To remove the cylinder Divide the product at the vibration damping unit for easier access to the cylinder Refer to To remove the vibration damping units on page 20 Tighten the engine body in a vise Use s...

Page 44: ...sh out the wrist pin by hand If it is tight use a small hammer and light force 5 Push the needle bearing out of the connecting rod 6 Remove the piston rings 6 8 4 Examine the cause of failure Examine the cause of low compression or failure With usual wear and many hours of operation components must be examined and replaced if necessary A product that has not been used for many hours must be 44 Rep...

Page 45: ...been worn smooth A product with a worn piston is difficult to start because of the decreased valve function of the piston 6 8 7 Piston wear tolerances 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 6 8 7 2 Piston ring groove If the piston ring groove is larger than 0 06 in 1 6 mm the piston must be replaced In...

Page 46: ... The scores are usually on the exhaust side which is the hottest The inlet side can show equivalent damage Examine the product to see if it has broken down because of an incorrect oil mixture or no oil at all If there is oil on a piston that is too hot it can carbonize If not check if the connecting rod or the crankcase has a thin layer of oil If there is sufficient oil inlet leakage can be the ca...

Page 47: ...e direction of the muffler when you assemble the piston on the connecting rod 2 Install the needle bearing in the connecting rod 3 Seal with a cloth or paper to make sure that parts do not fall into the crankcase 4 Install a snap ring in the piston 5 Hold the piston in position push in the wrist pin and install the other snap ring 1453 001 02 04 2020 Repair and servicing 47 ...

Page 48: ...n ring compressor 5 Push down the cylinder on the piston and let the piston ring compressor move along the piston Tighten the screws crosswise to a torque of 14 15 Nm 6 12 Crankcase 6 12 1 To examine the crankcase for leaks A crankcase with a leak has lower crankcase compression A typical sign is that the product cannot easily start There are special tools to seal the exhaust and inlet ports of th...

Page 49: ...tester increase the pressure to 7 psi 0 5 bar If the pressure decreases more than down to 3 psi 0 2 bar after 30 seconds there is a leakage 8 If there is a leakage apply a solution of soap and water or use a leakage spray to find it a Examine the seals on the crankshaft b Examine around the gaskets where the crankcase halves are bonded and at the bottom of the cylinder c Look for cracks on the cra...

Page 50: ...e crankcase seals 1 Apply leakage spray or a solution of soap and water to examine the seals for leaks 2 Use the pressure tester to find leaks 6 12 5 To disassemble the crankcase Divide the crankcase with a universal puller and a grip plate from Husqvarna Refer to Servicing tools overview on page 12 and Servicing tools overview on page 11 1 Disassemble the basic modules from the crankcase 2 Remove...

Page 51: ...ing tools overview on page 10 To replace the bearing you must use 2 Husqvarna bearing press kits Refer to Servicing tools overview on page 10 1 Put the puller plate behind the bearing Make sure that the plastic components on the balance weights are not damaged The puller must be in a position where the ears A are free The two parts of the puller head must not come nearer together than to the cente...

Page 52: ... it below the crankcase half 2 Put the screw through the washer and put the screw in the support plate 3 Lock the screw and turn the nut until the bearing is in the stop in the crankcase half 6 12 8 To assemble the crankcase Use the bearing press to press the crankshaft into the bearing Refer to Servicing tools overview on page 10 The mandrel threads for the clutch side is M10V and for the flywhee...

Page 53: ...Make sure that the connecting rod is not held against the crankcase half 5 Put the 2 guides in the holes 6 Install the new crankcase gasket 7 Assemble the other crankcase half using the same procedure a Change to the other mandrel b Make sure the position of the connecting rod is correct c Align the guides to prevent damage to the crankcase gasket d Put in the screws before the crankcase halves ar...

Page 54: ...he rear belt guard the air filter cover and the filter bracket 1 Lock the crankshaft with the piston stop 2 Release the clutch clockwise It is has a mark with the direction Off CAUTION Do not hit the puller This will break the piston If you use a hammer or equivalent without the piston stop the locking mechanism of the flywheel can become damaged 3 When the clutch is removed the clutch drum can be...

Page 55: ...ry 6 13 6 Belt pulley bearings The clutch drum and the belt pulley are connected units The belt pulley has 2 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 They are installed with a sliding fit against the crankshaft This means that the belt pulley can easily be pulled fro...

Page 56: ... pull out the bearings 6 13 8 To install the belt pulley bearings 1 Put the support plate of the bearings in a vise Put the 2 ball bearings on the support plate 2 Put the belt pulley on top of the bearings Put the cover and washers on top of the belt pulley Put the screw through the assembly 3 Tighten the screw to push the bearing in until the bearings are at the end in the belt pulley Note When y...

Page 57: ...ble the SmartGuard 1 Remove the springs from the front arms 2 Remove the plastic covers and the springs Discard the 4 screws 3 Remove the 4 screws and the bushings Discard the screws 4 Remove the SmartGuard 1453 001 02 04 2020 Repair and servicing 57 ...

Page 58: ...the 2 screws and remove the plates Discard the screws 6 Remove the 4 screws and the 2 wheels Discard the screws 7 Remove the arms 8 Remove the springs from the handle 58 Repair and servicing 1453 001 02 04 2020 ...

Page 59: ...semble the SmartGuard in opposite sequence CAUTION Discard and replace all self locking screws each time they are removed CAUTION Apply grease on the bushings Refer to Servicing tools overview on page 12 1453 001 02 04 2020 Repair and servicing 59 ...

Page 60: ...the product Refer to To remove the cutting head on page 15 2 Remove the bolt and the cutting blade 3 Put the cutting head in a vise with rubber jaws 4 Lock the belt pulley with a mandrel or a screwdriver and loosen the center screw 5 Remove the pulley 60 Repair and servicing 1453 001 02 04 2020 ...

Page 61: ...ction retarder slowly stops the cutting blade after operation It operates when below work speed The 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 The retarder does not operate A C D B 6 14 4 To disassemble the friction retarder 1 Remove ...

Page 62: ...f the guide plate 3 Assemble the brake shoes D with a pair of pliers 6 14 7 To assemble the retarder and belt pulley 1 Assemble the plate of the retarder unit and the belt pulley with the 4 screws 2 Put the retarder unit on the bearing housing Lock the belt pulley with a mandrel and put the center screw with the washer on the blade shaft 62 Repair and servicing 1453 001 02 04 2020 ...

Page 63: ... to Servicing tools overview on page 11 If you replace the bearings with a bearing press kit 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 A 2 Put the triangle from the bearing press kit or assembly support from the hydraulic press on top of the bearing Refer to Servic...

Page 64: ...t bearings with a bearing press kit use the Husqvarna bearing press kit Refer to Servicing tools overview on page 10 1 To assemble the blade shaft bearing with a hydraulic press a Put a piece of wood below the area for the blade shaft bearing to put the bearing housing in level position b Put the blade shaft bearing on the bearing housing and put the medium sized mandrel A from the Husqvarna press...

Page 65: ...g housing level 6 Put the axle with the blade shaft bearing in the bearing housing with the spacer down 7 Use a plastic hammer and push down the axle 6 15 Wet system 6 15 1 Function Each side of the blade guard has a spray nozzle The water hits a section of the cutting blade and the centrifugal force moves it out to the edge The spray nozzles are available with many different hole diameters 1453 0...

Page 66: ... the correct nozzle in the spare parts list 6 15 2 To disassemble the wet system 1 Remove the screws that hold the spray nozzle 2 Remove the filter with a wood screw 3 Remove the hose clip with a screwdriver 66 Repair and servicing 1453 001 02 04 2020 ...

Page 67: ...ove the throttle trigger lockout use a V jaw adjustable pliers Make sure that you hold the V jaw of the pliers adjacent to the handle Put a cloth on the throttle trigger lockout before you apply the pliers to prevent damage to the surface 1 Remove the carburetor Refer to To remove the carburetor on page 19 2 Push in the lower part of the throttle trigger lockout with a V jaw adjustable pliers 3 Li...

Page 68: ... 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 A winding in the ignition module A gives electric current to the OilGuard The analysis unit has a light em...

Page 69: ... the blue plug A with a screwdriver and replace it with an orange plastic plug B A B 6 17 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 1453 001 02 04 2020 Repair and servicing 69 ...

Page 70: ...e switch is OFF Set the switch to the left position The switch is defective Replace The primary wire is grounded Repair or replace There are sparks at the spark plug Problem Cause Solution Compression is good and fuel flows There is too much fuel Remove the fuel The carburetor is adjusted to give too rich mixture Repair adjust or replace the carburetor There is too much fuel mixture Adjust or repl...

Page 71: ... denly increases and then the engine stops There is no fuel Fill with fuel There is a blockage in the carburetor Clean 7 3 Engine stops during operation Remove the spark plug from the cylinder Hold the cylinder and pull the starter to see if there are sparks between the spark plug electrodes Problem Cause Solution Engine suddenly stops The engine runs lean Adjust repair or replace the carburetor D...

Page 72: ...ecreasing temperature Clean Blockage because of dirt on the cylinder fin Clean Low quality fuel is being used Replace with good quality fuel The level of carbon has increased in the com bustion chamber Clean The spark plug tip is red hot Champion RCJ 6Y NGK BPMR 7A Adjust to 0 5 mm Other The air filter is too dirty Replace the air filter Too high load Lower the load 7 5 Other engine problems There...

Page 73: ...g diagram 8 1 Wiring diagram OilGuard 3 2 2 3 1 1 1 1 2 3 3 2 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 ...

Page 75: ...1453 001 02 04 2020 Wiring diagram 75 ...

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Husqvarna K770 SmartGuard, Workshop Manual

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