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Husqvarna 545RXT AT Workshop Manual

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Workshop manual
545RXT AT, 545FX AT, 545FXT AT,
545FX, 545FXT, 545RX, 545RXT


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  Summary of Contents for Husqvarna 545RXT AT

  • Page 1 Workshop manual 545RXT AT, 545FX AT, 545FXT AT, 545FX, 545FXT, 545RX, 545RXT English...
  • Page 3: Table Of Contents

    Workshop manual Brushcutter, Trimmer Model 545RXT AT, 545FX AT, 545FXT AT, 545FX, 545FXT, 545RX, 545RXT 1 Introduction and safety instructions ..4 9.4 Removing the carburettor from engine unit ..31 9.5 Dismantling ............. 35 1.1 General ............. 4 9.6 Assembling ............38 1.2 Revisions ............
  • Page 4: Introduction And Safety Instructions

    Introduction and safety instructions 1 Introduction and safety instructions 1.1 General 1.4.2 Special safety instructions This workshop manual gives a full description of how to WARNING: Before you repair or do servic- do troubleshooting, repair and test of the product. It also ing on this product, please read and under- gives safety instructions that the personnel must obey stand the following warnings.
  • Page 5: Structure

    Start mode switch. clearly stated which tool to use in each section where it is needed. Always use Husqvarna original spare parts, service tools and accessories. Refuelling. Only use trimmer heads with trimmer cord 1.8 Symbols on the product...
  • Page 6: Technical Data

    Displacement Cylinder bore Stroke length Max. output/speed cm3/cubic inch Ø mm/Ø inch mm/inch kW/hp/rpm 545RXT AT 45.7 / 2.79 42 / 1.65 33.0 / 1.30 2.2 / 2.7 / 9000 545FX AT 45.7 / 2.79 42 / 1.65 33.0 / 1.30 2.2 / 2.7 /9000...
  • Page 7 Technical data Kg/lbs Max speed Idle speed Clutch diameter Engage speed mm/inch 545RXT AT 8700 2700 69 / 2.7 3900 545FX AT 9700 2700 69 / 2.7 3900 545FXT AT 9700 2700 69 / 2.7 3900 Drive gear Bevel gear ratio...
  • Page 8: Service Tools

    Service tools 3 Service tools 3 mm 4 mm 5 mm 8 – English...
  • Page 9 Service tools Pos. Description Used for Order No. Wrench T-handle, 3 mm General disassembly / assembly tasks 502 50 19-01 Wrench T-handle, 4 mm General disassembly / assembly tasks 502 50 18-01 Wrench T-handle, 5 mm General disassembly / assembly tasks 502 50 64-01 Test equipment Spark plug...
  • Page 10: Service Data

    Service data 4 Service data 0.5 ~ 1.0 Nm 4 mm 1 ~ 2 Nm 4 mm 6 ~ 7 Nm 4 mm 3 ~ 4 Nm 4 mm 2 - 3 Nm 4 mm Max. 0.5 Nm 3 ~ 4 Nm 4 mm 6 ~ 7 Nm 4 mm...
  • Page 11 Service data 57 ~ 78 Ncm 135 ~ 180 Ncm 2 ~ 3 Nm 4 mm 2 ~ 3 Nm 4 mm 57 ~ 78 Ncm 7 ~ 9 Nm 7 ~ 8 Nm 4 mm 3 ~ 4 Nm 4 mm 4 mm 7 - 9 Nm...
  • Page 12 Service data Lorem ipsum 14 ~ 16 Nm 16 mm 5 ~ 6 Nm 4 mm 3 ~ 4 Nm 4 mm 22 ~ 25 Nm 13 mm 4 ~ 5 Nm 4 mm 9 ~ 12 Nm 7 ~ 9 Nm 4 mm 4 mm 12 ~ 14 Nm...
  • Page 13 Service data 8 ~ 10 Nm 4 mm 5 ~ 10 Nm 13 mm 35 ~ 50 Nm 19 mm 1.5 ~ 2.5 Nm 4 mm 1.5 ~ 2.5 Nm 4 mm 1 ~ 2 Nm 4 mm 1.5 ~ 2.5 Nm 1 ~ 2 Nm 4 mm 0.5 ~ 1 Nm...
  • Page 14: Handle System

    Safety equipment 5 Handle system CAUTION: Always make sure that the stop switch and locking mechanism is fully functional after assembly. 5.1 Dismantling the stop switch 1. Carefully remove the stop switch (and heater switch, if equipped) using a flat screwdriver or similar tool. 2.
  • Page 15 Safety equipment Remove insulation (A) and disconnect all cables connections (B). Remove the plastic hat holding the stop switch cables in place (C). See figure 5. Fig. 5 5. Remove the securing plates (B) by gently twisting a screwdriver (A). See figure 6. 6.
  • Page 16: Assembling The Finger Throttle

    5.6 Assembling the finger throttle 1. Put all details in the left half of the handle. Make sure that the spring (A) and the throttle trigger (B) are attached correctly. See figure 8. 2. Make sure that all cables are put inside the handle and are not pinched.
  • Page 17 13. Make sure no cables are pinched between the handle halves and fasten the screws. See figure 11. Fig. 11 14. Connect the stop switch (A) and the heater switch (B) to the wiring harness and insert them in the handle.
  • Page 18: Replacing The Heating Elements In The Handles

    5.8 Replacing the heating elements in the handles The heating elements in the handles consist of ceramic plates that self-regulate the temperature. When the temperature increases, the resistance in the elements increases and the temperature lowers. No separate thermostat is needed. 1.
  • Page 19 6. Separate the contacts (A-A) and (B-B). 7. Extend the cables (A) and (B) with approximately 90 cm long steel wires attached to the contacts. This makes it easier to draw the cables to the new heating element back through the handle. 1 = black 2 = blue See figure 3.
  • Page 20: Muffler

    Muffler 6 Muffler 6.1 Dismantling WARNING: The muffler becomes very hot during operation. Do not touch the muffler until it has cooled down. 1. Remove the heat protector. 2. Remove the 3 screws that hold the muffler. 3. Remove the gasket. See figure 1.
  • Page 21: Starter

    Recoil pulley 7 Starter WARNING: Use protective glasses when working on the starter. The return spring has high tension and can cause injury. 7.1 Dismantling 1. Remove the 4 screws and lift off the starter. See figure 1. Note: The cylinder cover does not need to be loosened or detached.
  • Page 22: Assembling

    Recoil pulley 7.3 Assembling CAUTION: Open the package with the return spring (Fig. 6) carefully. It has high tension and can eject. CAUTION: Use protective glasses when Fig. 6 working on the starter. The return spring has high tension and can cause injury. 1.
  • Page 23: Ignition System

    Ignition system and heated handles 8 Ignition system CAUTION: The engine has an electronic ignition system without moving parts. A faulty component cannot be repaired and must be replaced. 8.1 Checking the ignition spark 8.1.1 Checking the spark plug The spark in an electronic ignition system has a very short burn time and can therefore be interpreted as weak and can be difficult to see while troubleshooting.
  • Page 24 Ignition system and heated handles 8.1.2 Do a check of the stop switch if there is no spark If there still is no spark after you replace the spark plug, remove the short-circuit cable from the stop switch. See figure 4. The stop switch can be easily detached with a screwdriver.
  • Page 25: Dismantling The Ignition Module

    Ignition system and heated handles 8.1.4 What to do if there still is no spark 1. Dismantle the starter and air guide plate, see “7.1 Dismantling” on page 21 Fig. 8 2. Adjust the air gap to the correct value. (See technical data) - Loosen the bolts.
  • Page 26: Dismantling The Flywheel

    Ignition system and heated handles 8.3 Dismantling the flywheel 1. Dismantle the starter, cylinder cover, muffler guard and the spark plug. 2. Remove air guide plate and disconnect the ignition connection. See figure 1. Fig. 1 3. Remove the drive dogs by unscrewing the two screws.
  • Page 27: Dismantling The Generator

    Ignition system and heated handles 8.5 Dismantling the generator 1. Disconnect the generator cable at the connection point. See figure 5. Fig. 5 2. Unscrew the two screws and remove the generator. See figure 6. Fig. 6 8.4 Replacing the drive dogs 1.
  • Page 28: Assembling The Flywheel And Ignition Module

    Ignition system and heated handles 8.6 Assembling the flywheel and ignition module 1. Inspect the key groove in the crankshaft for damage. If it is damaged, replace the crankshaft (Reference). See figure 9. 2. Inspect the key in the flywheel for damage. If it is damaged,replace the flywheel.
  • Page 29: Carburettor

    Carburettor 9 Carburettor WARNING: The fuel used in this product and the fuel vapor are dangerous. They can cause eye and skin irritation, breathing problems and are highly flammable. 9.1 Description The figures in this description do not correspond with the carburettor on the product.
  • Page 30 Carburettor In idling mode, the throttle valves (F) is closed and the choke valve (E) is open. Air is sucked in through an FUEL aperture in the throttle valve and a small amount of fuel is AIR/FUEL MIX supplied through the diffuser jet. See figure 3. Fig.
  • Page 31: Removing The Carburettor From Engine Unit

    Carburettor 9.4 Removing the carburettor from engine unit 1. Empty the fuel tank. 2. Loosen the screw on the starter and remove the cover on the tank unit, cylinder cover. See figure 6. 3. Loosen the air filter cover. See figure 6. Fig.
  • Page 32 Carburettor 7. Disconnect the connector between the AutoTune and ignition module and remove the clamps that hold the filter on the filter housing. See figure 10. Fig. 10 8. Remove the 2 upper screws holding the air filter housing. See figure 11. Fig.
  • Page 33 Carburettor 13. Remove the 2 screws from the filter house. See figure 14 Fig. 14 14. Remove the throttle wire from the throttle lever. See figure 15. Fig. 15 15. Make sure that the cable to the stop switch is loose from its holder.
  • Page 34 Carburettor 16. Lift up the carburettor and filter house. See figure 17. 17. Remove the fuel hose from the carburettor. CAUTION. Fuel will be drained if tank is not emptied. Fig. 17 18. Turn the throttle valve shaft to release the start switch from the activated position.
  • Page 35: Dismantling

    Carburettor 9.5 Dismantling See figure 20. Note: Do not remove the AT module from the carburettor. 1. Remove the 4 screws (A) that hold the metering diaphragm cover and lift off the cover. 2. Carefully remove the metering diaphragm (C), spiral support (D).
  • Page 36 Carburettor 6. To remove the inlet needle, loosen the screw and remove the metering lever, pin, inlet needle and spring. See figure 21. Fig. 21 7. Inspect the inlet needle for damage on the tip (A) and groove (B). See figure 22. 8.
  • Page 37 Carburettor 16. Use a screwdriver to remove the throttle lever (A) and a flat screwdriver to pry out the shaft extension (B). Inspect for damage and clean. See fig. 24. Fig. 24 English – 37...
  • Page 38: Assembling

    Carburettor 9.6 Assembling CAUTION: Make sure that the gasket surface is clean from old gasket residue and dust. See fig. 25. CAUTION: During assembly the pump diaphragm (B) shall be closest to the carburettor housing. See figure 26. 1. Attach the throttle lever and springs. 2.
  • Page 39 Carburettor 3. Attach the various parts of the metering unit in the opposite sequence as set out for dismantling. 4. Make sure that the lever arm lies 0.55 mm above gasket surface of the carburettor housing. (See special tools pos. 10).
  • Page 40: Assembling The Carburettor On The Engine Unit

    Carburettor 9.7 Assembling the carburettor on the engine unit 1. Make sure that the spring is in its place in the start switch (A). 2. Place the shaft extension into the start switch (B). 3. Place the carburettor in the filter house (C) and activate the start switch.
  • Page 41 Carburettor 10. Install the throttle wire on the throttle lever. See figure 34. Fig. 34 11. Make sure that the valve housing assembly gasket is not damaged. See figure 35. Fig. 35 12. Install the connecting rod to the carburettor. See figure 36, Pos A.
  • Page 42 Carburettor 14. Install the 2 upper screws that holds the housing assembly and the filter holder. See figure 37. Fig. 37 15. Install the filter into the filter holder and attach the clamps that hold the filter. See figure 38. 16.
  • Page 43 Carburettor Note: Do not use any sharp tools. CAUTION: Tighten screws according to service data. 21. Tighten the frame using M5*16 screws in the bottom of the frame (A). See figure 42. For correct torque, see service data. 22. Tighten the frame using M5*12 screws in the upper part of the frame (B).
  • Page 44: After Replacing The Carburettor Autotune

    Carburettor 9.8 After replacing the carburettor AutoTune WARNING! When the engine is tested in connection with carburettor adjustment, the clutch and clutch cover must be mounted together with the shaft and gear head. A loose clutch can result in serious personal injury. NOTE! Do not remove the AutoTune unit from the carburettor.
  • Page 45: Fuel System

    Fuel system 10 Fuel system In addition to the fuel tank and carburettor, the fuel system consists of the air filter, fuel pump, fuel filter and tank venting. 10.1 Dismantling the air filter 1. Remove the cover (A) and remove the air filter (B). See figure 1.
  • Page 46: Tank Venting

    Fuel system 10.3 Tank venting Tank venting is done through the fuel cap and needs to be functional for the engine to work. 1. Remove the cover over the fuel pump and the fuel hose from the carburettor. Drain the fuel from the tank.
  • Page 47: Replacing The Air Purge And Fuel Filter

    Fuel system 10.5 Replacing the air purge and fuel filter The air purge facilitates the start of the engine when it is cold. The fuel pump fills the carburettor with fuel before the engine is started. The fuel pump also prevents blockage of vapor bubbles in the narrow fuel channels.
  • Page 48: Centrifugal Clutch

    Centrifugal clutch 11 Centrifugal clutch The centrifugal clutch has the task of transferring the power from the engine to the drive axle of the cutting equipment. As the name implies, it works according to a centrifugal principle. This means the friction shoes of the clutch are thrown in the direction of the clutch drum at a certain engine speed. When the friction against the drum is sufficient, it drives the drive shaft at the same speed as the engine.
  • Page 49: Dismantling Clutch Assembly

    Centrifugal clutch 8. Remove the vibration dampers. See figure 4. 9. Remove the 4 screws holding the clutch cover on the engine. See figure 4. 10. Lift the engine body to the side so that the clutch becomes accessible. Fig. 4 11.2 Dismantling clutch assembly S/N: -191300901 Note! If the clutch hub is undamaged, this step is...
  • Page 50: Dismantling Clutch Shoes And Springs

    11.3 Dismantling clutch shoes and springs WARNING: Use protective glasses when working on the clutch. The springs might have high tension and can cause injury. 1. Remove the three bolts. See figure 6. CAUTION! Do not lose the sleeve bearings found in the clutch shoes.
  • Page 51: Assembling Clutch Shoes And Springs

    Centrifugal clutch 11.5 Assembling clutch shoes and springs WARNING: Use protective glasses when working on the clutch. The springs might have high tension and can cause injury. 1. Temporarily place the clutch shoes on the clutch hub and loosely tighten the screws. Fig.
  • Page 52: Clutch Drum

    Clutch drum 12 Clutch drum 12.1 Dismantling Separate the engine body and shaft as described in “11.1 Dismantling” on page 48. 1. Loosen the two screws (A) holding the clutch cover against the shaft. See figure 1. 2. Loosen the screw (B) preventing the shaft from rotating.
  • Page 53: Inspection

    Clutch drum 12.2 Inspection 1. Inspect the clutch drum for wear and damage. 2. Replace the clutch drum if the diameter exceeds 70.5 mm. See figure 5. Fig. 5 12.3 Assembling WARNING: Always use gloves when handling hot objects. 1. Heat the clutch housing to approximately 110 °C using a hot air gun.
  • Page 54: Gear Head

    Gear head 13 Gear head The gear head has 2 purposes: The first is to gear down the high engine speed to better suit the lower speed a saw blade or trimmer requires to work efficiently. Second, the gear head contributes to the saw operator’s working stance so that it is comfortable and at the same time efficient.
  • Page 55 Gear head 9. Remove the lubricant top-up plug and warm the entire gearbox using a hot air gun to about 150°C. 10. Knock the gearbox against a wooden block so that the input axle and bearing fall out. See figure 4. NOTE! The input axle with pinion must be dismantled first.
  • Page 56: Assembling

    Gear head 13.1 Assembling 1. Replace damaged parts. 2. Assemble the gear head in the opposite sequence as set out for dismantling. See figure 6. 3. Fit the bearings on their respective axles. It is easier if the bearings are heated to approx. 100°C. Note: Do not forget the circlip holding the bearing on the input axle.
  • Page 57: Cylinder And Piston

    Cylinder and piston 14 Cylinder and piston The cylinder and the piston are 2 of the components exposed to most strain in the engine. They must withstand, for example, high speeds, large temperature swings and high pressure. Moreover, they must be resistant to wear. CAUTION! When servicing these components, cleanliness is of the utmost importance.
  • Page 58: Cleaning And Inspection

    Cylinder and piston 7. Use a long-nosed pliers to remove the G circlip from the gudgeon pin. Keep your thumb over the circlip to prevent it from flying out. See figure 4. Fig. 4 8. Push the gudgeon pin from the piston using a punch See Service tools, pos.
  • Page 59: Pressure Testing The Cylinder

    14.3 Pressure testing the cylinder At minimum, dismantle the following components • Cylinder cover • Heat protector • Muffler • Air filter cover and frame • Spark plug • Valve housing assembly • Carburettor (with air filter and filter holders) Fig.
  • Page 60: Assembling

    Cylinder and piston 14.4 Assembling CAUTION! Place a rag in the crankcase opening to prevent the circlip from falling into the crankcase. 1. Lubricate the needle bearing of the gudgeon pin with a few drops of engine oil. 2. Direct the arrow on the top of the piston towards the exhaust port.
  • Page 61: Analysis And Actions

    Cylinder and piston 14.5 Analysis and actions With help of the illustration and the accompanying description, note the reasons for the breakdown, repair the damage and take the actions required to prevent the same thing happening again. 14.5.1 Insufficient lubrication The piston has small to medium size score marks usually in front of the exhaust port.
  • Page 62 Blocked air intake on the starter. Blocked spark arrestor mesh in the muffler. Clean or replace the spark arrestor mesh. For the best results we recommend Husqvarna two- stroke oil or ready-mixed fuel that is specially developed for air-cooled two-stroke engines.
  • Page 63 Cylinder and piston 14.5.2 Piston scoring caused by heavy carbon deposits Too heavy carbon depositing can cause damage similar to that caused by insufficient lubrication. However, the piston skirt has a darker colour caused by the hot combustion gases that are blown past the piston. This type of piston damage starts at the exhaust port where carbon deposits can become loose and get trapped between the piston and the cylinder wall.
  • Page 64 Cylinder and piston 14.5.5 Piston ring guide pin vibrated loose A too high engine speed can cause the ends of the piston ring to hammer against the guide pin when the piston ring moves in its groove. The intensive hammering can drive out the pin through the top of the piston causing serious damage also to the cylinder.
  • Page 65 Cylinder and piston 14.5.6 Damage caused by gudgeon pin circlips A too high engine speed can cause the gudgeon pin circlips to vibrate. The circlips are drawn out of their grooves due to the vibrations, which in turn reduces the tensioning power of the circlips.
  • Page 66 Cylinder and piston 14.5.8 Foreign objects Everything other than clean air and pure fuel that enters the inlet port of the engine causes some type of abnormal wear or damage to the cylinder and piston. This type of increased wear shows on the inlet side of the piston, starting at the lower edge of the piston skirt.
  • Page 67 Cylinder and piston Larger, softer particles that penetrate into the engine cause damage to the piston skirt under the piston ring as the illustration shows. The piston scored and worn from the piston ring down on the inlet side. Cause: Action: Air filter incorrectly fitted.
  • Page 68 Cylinder and piston 14.5.9 Service tips Broken cooling fins, damaged threads or sheared bolts In severe cases – replace the cylinder. by the exhaust port. Repair the threads using Heli-Coil. Seizure marks in the cylinder bore (especially by the Polish the damaged area using a fine grade emery cloth exhaust port).
  • Page 69: Crankshaft And Crankcase

    Crankshaft and crankcase 15 Crankshaft and crankcase The task of the crankshaft is to transform the reciprocating motion of the piston to rotation. This requires a stable design withstanding immense pressure and rotational and bending strain, as well as high rotational speed. In addition the connecting rod is exposed to large acceleration and retardation forces as it moves between the top and bottom dead centres.
  • Page 70 Crankshaft and crankcase 3. Remove the 5 screws that hold both crankcase halves together. See figure 2. Fig. 2 4. Separate the crankcase halves from each other. See figure 3. This can be done without tools as the crankshaft has a sliding fit in the bearing seatings. Fig.
  • Page 71: Inspection

    Crankshaft and crankcase 15.2 Inspection 1. The crankshaft cannot be reconditioned and must be replaced if it is worn or damaged. 2. Inspect the large end of the connecting rod. If seizure marks, discolouration on the sides or damaged needle holders are found the crankshaft must be replaced.
  • Page 72: Assembling

    Crankshaft and crankcase 15.3 Assembling WARNING: Always use protective gloves when handling hot objects. 1. Heat the crankcase halves to approx. 150°C using a hot air gun and position the bearings. See figure 8. 2. Press the bearing into the crank case. Make sure they go right down into the bearing seats.
  • Page 73 Crankshaft and crankcase CAUTION! Assembly tools must be used when assembling sealing rings. Make sure the tool is not damaged in any way. Do not use a faulty tool. Fig. 12 8. Assemble tool (See Service tools, pos. 20) on crank shaft.
  • Page 74: Troubleshooting

    16 Troubleshooting Starter rope Defect does not retract Perform “Cleaning and in- Change part or com- spection” of starter housing plete starter if needed. starter housing (see separate instr.) Sticking starter Change part or com- Defect starter housing housing plete starter if needed. Start rope stuck Check air gap between fly- Change part if needed.
  • Page 75: Engine Running Issue

    Cylinder gasket Intake system Cylinder Does the Crankcase gaskets engine Crankcase start ? Issue still remains? Perform a visual inspection of interface Contact your Husqvarna between carburettor and intake rubber for Local Sales Company for leakage. advice. English – 75...
  • Page 76 Check cables and connectors for wear. Product OK Check torque on ignition coil screws. Check the ground wire. Issue still remains? Contact your Husqvarna Local Sales Company for advice Leakage Check function of decompression valve (if equipped). Check mounting/interface intake rubber and carburettor.
  • Page 77: Ignition System Diagnostic Flow Chart

    16.2 Ignition System Diagnostic Flow Chart Perform visual inspection of unit. Inspect spark plug wire, boot connections. Repair/replace any problem items. Install new, properly gapped, manufacturer specified spark plug. Stop switch must be in run position. Perform Spark Test (See separate instructions). End Test Does engine Remove spark...
  • Page 78: Spark Test

    16.3 Spark Test 1. Disconnect the spark plug from the cylinder. 2. Connect Ignition Tester to spark plug cap and ground the clip to the cylinder fins, see illustra- tion. 3. Adjust the knob to 6 mm gap between the two electrodes, read 6 marks on the corresponding scale.
  • Page 79 English – 79...
  • Page 80 115 88 11-26 2018-10-04...

This manual is also suitable for:

545fx at545fxt at545fx545fxt545rx545rxt