Husqvarna 243RJ Workshop Manual
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Workshop manual
243RJ 253RJ


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Summary of Contents for Husqvarna 243RJ

  • Page 1 Workshop manual 243RJ 253RJ English...
  • Page 3: Table Of Contents

    3. Fuel system ______________________________ 15 4. Centrifugal clutch __________________________ 29 5. Angle gear _______________________________ 35 6. Cylinder and piston ________________________ 41 7. Crankshaft and crankcase __________________ 51 8. Tools ___________________________________ 57 9. Technical Data ___________________________ 61 © Husqvarna AB, Sweden 2010...
  • Page 4: General Recommendations

    Operator’s Manual. The assembly of other equipment or accessories or spare parts not approved by Husqvarna can Special tools result in the failure to meet these safety demands and that the person carrying out assembly bears responsibility for this.
  • Page 5: Starter

    Starter Starter Contents Dismantling ___________________________________ 4 Assembly _____________________________________ 5 Replacing the drive _____________________________ 7...
  • Page 6 Starter WARNING! Protective glasses should be worn when working on the starter to avoid injury to the eyes if, for some reason, the return spring should fl y out. Dismantling Dismantling Dismantle the cylinder cover to make sub- To make subsequent starter assembly sequent starter assembly easier.
  • Page 7 Starter Loosen the spring tension. Loosen the spring tension. Lift up the starter cord on the starter pul- Pull out the starter cord about 30 cm. ley and allow it to rotate backwards until Slow the starter pulley with your thumb. the spring tension ceases.
  • Page 8 Starter Fit the new starter cord, pressure equali- Fit the new starter cord (length 900 mm). sation spring and drive disc. Tighten the screw in the centre of the pulley. NOTE! Replace any starter cord without removing the starter pulley. Make sure the knot is as small as possible and goes down into the notch in the pulley.
  • Page 9 Starter Replacing the drive disc Replacing the drive disc Dismantle the drive disc using a hammer The drive disc is threaded on the crank- and a mandrel. shaft. Loosen the drive disc using a hammer and a mandrel. TIP! TIP! The drive disc can sit very tightly on the shaft.
  • Page 10 Starter...
  • Page 11: Electrical System

    Electrical system Electrical system Contents Checking the ignition spark ___________________10 Dismantling _______________________________11 Assembly _________________________________12...
  • Page 12 Electrical system The engine is equipped with an electronic ignition system completely without moving parts. Consequently, a faulty component cannot be repaired, but must be replaced by a new component. The spark in an electronic ignition system has a very short burn time and can therefore be interpreted as weak and can be diffi...
  • Page 13 Electrical system Still no spark? If there is still no spark, remove the car- burettor cover and disconnect the short- Dismantle the short-circuit cable from the circuit cable. ignition switch. Dismantle the contact by prizing it away Still no spark? from the throttle handle using a knife and Check the short-circuit cable using an remove one of the short-circuit cables...
  • Page 14 Electrical system Still no spark? Still no spark? Check other cables and connections. Check other cables and connections for poor contacts (dirt, corrosion, cable brea- kage and damaged insulation). See chapter 3 “Throttle”. TIP! Use an Ohmmeter in order to easily check if cable breakage has occurred, due to pinching, for example.
  • Page 15 Electrical system Remove the 4 screws and remove the Remove the 4 screws holding the clutch entire shaft unit. cover against the crankcase. Lift out the entire shaft unit. 502 71 27-02 Dismantle the ignition module and the Remove the screws (A) holding the igni- centrifugal clutch.
  • Page 16 Electrical system Assembly Check that the key way in the fl ywheel and the key way in the crankshaft are undamaged, as well as the key. Fit the fl ywheel and centrifugal clutch. Do not forget the fl at spacers (A). NOTE! Turn the clutch so that the arrows (B) that indicate the direction of rotation...
  • Page 17: Fuel System

    Fuel system Fuel system Contents Air fi lter __________________________________16 Tank venting ______________________________16 Fuel fi lter _________________________________17 Fuel pump _______________________________17 Carburettor _______________________________17 Carburettor settings________________________ 24 Throttle handle ___________________________ 26 Trouble Shooting Guide ____________________ 28...
  • Page 18: Air Fi Lter

    Brush the fi lter clean or blow it clean with compressed air. Remove the pre-fi lter (C) which is made of foam and wash it in lukewarm soapy water or Husqvarna Active Cleaning 505 69 85-70. Tank venting Tank venting takes place through the fuel...
  • Page 19: Fuel Fi Lter

    Fuel system Fuel fi lter NOTE! The fuel fi lter can be removed through the There is a small slit (G) in the non- tank’s fi ll hole. return valve (B) that only becomes visible when you carefully squeeze its sides. If the valve is undamaged, the slit is not visible in its normal position.
  • Page 20 Fuel system The blending unit The blending unit Fuel and air are mixed here. In this section of the carburettor fuel and air are mixed in the proper proportions. The choke and throttle valves are placed here. In the middle of the venturi (narrowest part of the throughput) the main jet (D) is found.
  • Page 21 Fuel system Dismantling the carburettor Dismantling the carburettor Remove the control diaphragm and check Remove the 4 screws holding the control for damage. diaphragm cover and lift off the cover. Replace if required. Carefully remove the control diaphragm (A) and gasket (B). Check the diaphragm for holes and wear on the pin (C).
  • Page 22 Fuel system Check the needle valve and the lever arm Check the needle valve for damage on the for damage or wear. tip and in the lever arm groove. Replace damaged components with new Check the lever arm for damage to the ones.
  • Page 23 Fuel system Pull out the locking plug (A) above the jet needles using special tool 504 62 29-01. The plugs cannot be dismantled if there is no pin on the plug in the middle of the slot (B) in the carburettor housing. Unscrew the jet needles.
  • Page 24 Fuel system Fit the jet needles and adjust their setting. Model 243 RJ 253 RJ 253 RJ WT841D WT795F WT795G Carburettor 3 3/4 2 1/8 2 1/8 L-needle 1 1/8 3 1/8 2 7/8 H-needle A tolerance of ± 1/2 turn applies to all needle installations.
  • Page 25 Fuel system 5. Pump diaphragm (F). 5. Pump diaphragm (F). Make sure this is aligned properly so the impulse chan- 6. Gasket (H). nel (G) is open. 7. Cover (I). 6. Gasket (H). 8. Hook in the connecting rod (J). 7.
  • Page 26: Carburettor Settings

    Fuel system 13. Fit the distance piece onto the cylinder. 13. Check the impulse channel (A) in the distance piece is open. Replace gasket where necessary and fi t the distance piece onto the cylinder using the 3 screws. 14. Fit the “rubber connection” onto the distance piece.
  • Page 27 Fuel system Basic setting The carburettor is set to its basic setting when test run at the factory. The basic setting is “richer” than the optimal setting (fast idle speed is 600–800 rpm under the recommen- ded max. speed) and should be kept during the engine’s fi rst working hours. Thereafter the carburettor should be fi...
  • Page 28: Throttle Handle

    Fuel system Adjust the carburettor jet screws as follows after making the NOTE! basic adjustment: Speed in excess of 12,000 rpm should be restricted 1. Run the engine warm for approx. 3.5 minutes. Adjust the idle by the ignition system and not recorded by the speed to 2,800 rpm where necessary using a T screw.
  • Page 29 Fuel system 6. Lift out the throttle control (D). 7. Lift off the starter throttle catch (E). 8. Disconnect both contact pins (F) from the ignition switch (G). 9. Dismantle the ignition switch by prizing it away using a knife or squeeze the locking springs together whilst simulta- neously pressing the contact out of the throttle handle half.
  • Page 30: Trouble Shooting Guide

    Fuel system Trouble Shooting Guide Symptom Starting Low speed Acceleration/ Deceleration/ Probable causes ● ● ● ● Stop screw for the throttle not working ● ● ● ● ● ● ● Fuel tank/hose Fuel fi lter blocked ● ● ● ●...
  • Page 31: Centrifugal Clutch

    Centrifugal clutch Centrifugal clutch Contents Centrifugal clutch _________________________ 30 Clutch drum and drive axle __________________ 31...
  • Page 32 Centrifugal clutch The centrifugal clutch has the task of transferring the power from the engine to the cutting equipment’s drive axle. As the name implies, it works according to a centrifugal principle. This means the clutch’s friction shoes are thrown outwards towards the clutch drum at a certain engine speed.
  • Page 33 Centrifugal clutch Twist apart the clutch. Twist apart the clutch and inspect the spring and lining with regard to wear and Inspect and replace damaged or worn damage. parts. The thickness of the lining must be at least 1.0 mm at the most worn point. NOTE! Both clutch shoes should be replaced even if only one of them is...
  • Page 34 Centrifugal clutch Remove the circlip (E) and push out the 4. Remove the circlip (E). AV element by prizing is out with a screw- 6. Use a screwdriver and carefully prize driver. out the AV element (F) together with the shaft mounting (G). 7.
  • Page 35 Centrifugal clutch Assemble the clutch housing in the re- verse order as set out for dismantling and note the following: – Rub the vibration damper with talc, silicon or soapy water to facilitate as- sembly. – Make sure the AV element with notch (A) aligns with the screw hole for the locating screw.
  • Page 36 Centrifugal clutch...
  • Page 37: Angle Gear

    Angle gear Angle gear Contents Bevel gear, type 1, dismantling _______________ 36 Bevel gear, type 1, assembling _______________ 37 Bevel gear, type 2, dismantling ________________38 Bevel gear, type 2, assembling ________________39...
  • Page 38 Angle gear The angle gear has two purposes: The fi rst is to gear down the engine’s high speed to better suit the lower speed a saw blade or trimmer requires to work effi ciently. Secondly, the angle gear contributes towards the operator’s working stance so that it is comfor- table and at the same time effi...
  • Page 39 Angle gear Dismantle the bearings from the output Dismantle the bearings from the output and input axles. and input axles with the help of a small bearing puller. TIP! Hold the bearing puller in a vice so that it gains a better grip around the bearing. Assembly Clean all component parts and replace if damaged or worn.
  • Page 40 Angle gear Bevel gear, type 2 Bevel gear, type 2 Dismantling Dismantling Remove the bevel gear from the shaft. Dismantle the cutting attachment with respective guard. 1. Remove screws (A) and (B) and lift off the plate (C). 2. Loosen screws (D) and remove the bevel gear from the shaft.
  • Page 41 Angle gear Output shaft Output shaft Dismantle the ball bearing and the cog- Dismantle the ball bearing and the cog- wheel from the shaft. wheel from the shaft. The pulling device is not required. Input shaft Input shaft Dismantle the circlip and remove the ball Dismantle the circlip and remove the ball bearing from the shaft.
  • Page 42 Angle gear Input shaft The input shaft should be fi tted after the output shaft has been fi tted. 1. Fit the ball bearings on the axle. Do not forget the circlip holding the ball bearings in place. 2. Warm the gear housing some more if 2.
  • Page 43: Cylinder And Piston

    Cylinder and piston Cylinder and piston Contents Dismantling ________________________________ 42 Cleaning, inspection _________________________ 43 Analysis and actions _________________________ 43 Service tips ________________________________ 48 Wear tolerances ____________________________ 48 Assembly __________________________________ 49...
  • Page 44: Dismantling

    Cylinder and piston The cylinder and the piston are two 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. Despite these tough working conditions, major piston and cylinder failure is relatively uncommon.
  • Page 45: Cleaning, Inspection

    Cylinder and piston Cleaning, inspection After dismantling, clean the individual components: 1. Scrape carbon deposits from the top of the piston. 2. Scrape carbon deposits from the cylinder’s combustion chamber. 3. Scrape carbon deposits from the cylinder’s exhaust port. NOTE! Scrape carefully with not too sharp a tool so as not to damage the soft aluminium parts.
  • Page 46 Blocked spark arrestor mesh in the Clean or replace the spark arrestor mesh. muffl er. For the best results we recommend Husqvarna two-stroke oil or ready-mixed fuel that is specially developed for air-cooled two-stroke engines. Mixing ratio: 1:50 (2%). If Husqvarna two-stroke oil is not available another good quality two-stroke oil can be used.
  • Page 47 Cylinder and piston Piston damage caused by a too high engine speed. Typical damage from too high engine speed is ruptured piston ring/piston rings, broken circlip on the gudgeon pin, faulty bearings or that the guide pin for the piston ring has become loose.
  • Page 48 Cylinder and piston Foreign objects Everything other than clean air and pure fuel that enters the engine’s inlet port causes some type of abnormal wear or damage to the cylinder and piston. This type of increased wear shows on the piston’s inlet side starting at the lower edge of the piston skirt.
  • Page 49 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. Action: Cause: Fit the air fi lter correctly. • Air fi lter incorrectly fi tted. Fit a new air fi...
  • Page 50: Service Tips

    Cylinder and piston Service tips Action: Defect: In severe cases – replace the cylinder. Broken cooling fi ns, damaged threads or sheared bolts by Repair the threads using Heli-Coil. the exhaust port. Polish the damaged area using a fi ne grade emery cloth so Seizure marks in the cylinder bore (especially by the ex- that the coating of aluminium disappears.
  • Page 51: Assembly

    Cylinder and piston Assembly Assembly Lubricate the gudgeon pin’s needle bea- Lubricate the gudgeon pin’s needle bea- ring with a few drops of engine oil. ring with a few drops of engine oil. Direct the arrow on the top of the piston towards the exhaust port.
  • Page 52 Cylinder and piston...
  • Page 53: Crankshaft And Crankcase

    Crankshaft and crankcase Crankshaft and crankcase Contents Dismantling ________________________________ 52 Inspecting the crankshaft ______________________ 53 Assembly _________________________________ 54...
  • Page 54 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 55 Crankshaft and crankcase Dismantle the ball bearing from the crank- Dismantle the ball bearing from the crank- shaft. shaft using a suitable pulling device. 504 90 90-01 Dismantle the sealing ring on the crank- Dismantle the sealing ring on the crank- case half on the fl...
  • Page 56 Crankshaft and crankcase Inspect the small end of the connecting Inspect the small end of the connecting rod. rod. If seizure marks or discolouration are found in the bearing track the crankshaft must be replaced. Check the crank bearing. Check the crank bearing. The connecting rod shall not have any radial play (up and down).
  • Page 57 Crankshaft and crankcase Use a hot air gun to gently warm the inner Fit the crankshaft in the crankcase half on ring of the ball bearing on the crankcase the fl ywheel side. half of the fl ywheel side. Lubricate the shaft pin with a few drops of oil and push carefully into the crankshaft in the ball bearing.
  • Page 58 Crankshaft and crankcase Check that the pulse channel in the cylin- Check that the pulse channel in the cylin- der is open. der is open. Assemble the cylinder with the help of as- Place a new gasket on the base of the sembly set 502 50 70-01.
  • Page 59: Tools

    List of tools Tools Contents Starter __________________________________ 58 Electrical system __________________________ 58 Fuel system ______________________________ 58 Centrifugal clutch __________________________ 58 Angle gear _______________________________ 59 Cylinder and piston ________________________ 59 Crankshaft and crankcase ___________________ 59 Workshop equipment _______________________ 59...
  • Page 60 List of tools 502 71 14-01 502 71 27-02 505 69 85-70 502 71 27-02 502 71 13-01 531 03 06-23 502 71 27-02 502 50 06-01 502 51 49-02 502 50 83-01 531 00 48-63 501 60 02-03 502 71 27-02 504 62 29-01 502 51 34-02...
  • Page 61 List of tools 502 50 18-01 502 71 27-02 502 71 27-02 502 51 03-01 544 13 05-01 503 97 64-01 502 50 70-01 544 13 08-01 505 38 17-05 531 03 06-23 502 71 27-02 502 50 70-01 504 91 28-00 502 71 14-01 544 13 09-01 504 91 28-00...
  • Page 62 List of tools...
  • Page 63: Technical Data

    Technicel data Technical data Contents Engine __________________________________ 62 Ignition system ____________________________ 62 Carburettor ______________________________ 62 Clutch __________________________________ 62 Driving __________________________________ 62 Dimensions ______________________________ 62...
  • Page 64 Technicel data Engine 243 RJ 253 RJ Displacement, cm 40,1 50,6 Cylinder bore, mm 40,5 45,5 Stroke, mm 31,1 31,1 Compression ratio Max output, kW / speed, rpm 1,47 / 9000 2,3 / 9500 Ignition system Digital CDI IKEDA CDI OPPAMA CDI Spark plug, NGK CMR7H-10...
  • Page 66 115 38 22-26 2010W38...

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