Husqvarna 50 Rancher Workshop Manual Download

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50, 50 Special, 51, and 55

Workshop Manual

531 03 00-76

Summary of Contents for 50 Rancher

Page 1: ...50 50 Special 51 and 55 Workshop Manual 531 03 00 76 ...

Page 2: ...how to repair the saw and how to use special tools In order to make sure that the saw will function properly always use Husqvarna original spare parts and accessories The information specifications and illustrations in this manual are based on the information in effect at time of printing Any improvements or changes on these models will be included in future manual revisions ...

Page 3: ...ervice Tools 4 Safety Equipment 5 Rewind Starter 6 Ignition System 7 Centrifugal Clutch 8 Lubrication System Oil Pump 9 Anti Vibration System 10 Fuel System Exhaust System 12 Cylinder Piston 13 Crankcase Crankshaft 2 3 3 4 12 15 22 26 30 32 47 46 51 ...

Page 4: ...7Y BPMR6A 0 5 0 020 Fuel and Lubrication System Carburetor Walbro WA82 WA82 WT170 WTl 70 Fuel tank volume Iitre pint 0 6 1 27 0 6 1 27 0 6 1 27 0 6 1 27 Oil tank volume Iitre pint 0 3 0 63 0 3 0 63 0 3 0 63 0 3 0 63 Oil pump capacity at 6000 rpm cc rein 7 0 7 0 7 0 7 0 Oil pump type Automatic Automatic Automatic Automatic Bar and Chain Bar length cm inch Chain pitch Chain speed 325 m see 3 8 m see...

Page 5: ...1 5025046 01 5025070 01 5025079 01 5025083 01 5025087 01 5025099 01 5025134 02 5025161 01 5025191 01 5025194 01 5027113 01 5027114 01 5049029 02 5049090 01 5052679 12 Assembling pliers spark plug Allen key 4 mm Allen key 3 mm Socket spanner 8 mm Puller complete Crankshaft installation device Model 50 serial 9250857 and up Crankshaft installation device Piston Stop Pressure gauge Sleeves 2 pieces P...

Page 6: ... it may dislodge without warning Eye protection must be worn during disassembly and reassembly of the chain brake Chain Brake Disassembly Disengage chain brake Remove clutch cover retaining nuts and withdraw cover from the chain saw Clean chain brake and clutch cover assembly Engage the chain brake by moving the hand guard forward Remove hand guard retaining screw Rethread screw into pivot sleeve ...

Page 7: ...om cover Remove the five screws and lift off the cover plate CAUTION The spring is under tension Always wear safety goggles for eye protection Using the tip of a flat bladed screwdriver carefully lift the end of spring out of the cover Press out the pin which holds the linkage arm using a suitable punch ...

Page 8: ...ke band is 0 80 mm 0 031 in The brake band must be exchanged if the band is worn anywhere along its length to 0 65 mm 0 026 in or less If the brake band needs to be exchanged separate the band from the linkage by removing the screw Assembly Check all chain brake parts for wear or damage and replace with new parts if necessary Lubricate the linkage and pivots with thin oil ...

Page 9: ...s up as shown in photo Insert the linkage and band assembly into the cover Secure the knee link to the cover with the retaining pin Slide the brake spring over the linkage spring post Using a flat bladed screwdriver depress the spring then carefully press the spring end into the cover Install the cover plate ...

Page 10: ... brake engages With the brake engaged it should not be possible to rotate the saw chain around the guide bar Pull the hand guard back towards the front handle to disengage the brake Inertia Chain Brake Function WARNING The engine must be stopped for the following test With the engine stopped hold the chain saw with both hands With the chain saw horizontal position the bar tip approx 35 cm 14 in ab...

Page 11: ...the engine Hold the handles with both hands and apply full throttle Activate the chain brake by turning your left wrist against the hand guard The saw chain should stop moving immediately Throttle Trigger Lockout Disassembly Press out the pin On the 50 and 50 Special models the throttle lockout lever has a small tab midway on the left side Insert a small screwdriver between the lever and lever ope...

Page 12: ...nhook the spring Assembly Insert the spring down through the recess in the handle Hook the spring onto throttle trigger Align the pin hole in the trigger with the corresponding hole in the handle and install the pin Insert the lockout lever making sure the end of the spring fits within the lever ...

Page 13: ...ever NOTE On 51 and 55 models the fast idle system is integrated into the choke system When the choke knob is pulled the fast idle is engaged for starting purposes When the throttle trigger is depressed the fast idle system disengages allowing the engine to return to idle when the trigger is released Chain Catcher Check the chain catcher If the chain catcher is missing or damaged install a new cat...

Page 14: ...Special models engage rope in pulley notch On 51 and 55 models pull rope up between any notched section in pulley Carefully and slowly release the pulley to allow the rewind spring to unwind Remove pulley retaining screw from the starter post and remove the pulley Carefully withdraw the recoil spring cassette Clean all parts before assembly WARNING Be very careful when removing and installing the ...

Page 15: ...ugh the rope eyelet in the housing and the starter grip Tie the rope at the starter grip end with a double loop knot Install the new recoil spring cassette into the housing Lubricate the starter post with cold resistant grease Wind 3 turns of the starter cord in a clockwise direction onto the pulley Install the rope pulley washer and retaining screw ...

Page 16: ...of a turn further when the starter cord is pulled to the end of rope travel To install the starter assembly on crankcase first pull the starter grip out approximately 15 cm 6 in then position the housing against the crankcase Release the grip so that the pulley engages the starter pawls on the flywheel Install and tighten the four starter retaining screws ...

Page 17: ...ion system the spark will appear to be weaker compared to breaker point ignition systems due to the shorter arc duration time Spark Plug Champion RCJ7Y and NGK BPMR6A are the only spark plugs that should be used The spark plug should be removed cleaned and inspected at least once a week The spark plug electrode gap should be 0 5 mm 0 020 in If the electrodes are worn install a new properly gapped ...

Page 18: ...e short circuit wire from the stop switch Check for spark again as previously described If spark occurs the stop switch is defective and should be replaced If no spark is evident carefully inspect the full length of the short circuit wire and the high tension lead to the spark plug Ensure that short circuit wire isn t pinched or grounded against any metal surface i e crankcase cylinder Check the h...

Page 19: ... retaining screws Remove the air gap tool and recheck for spark If no spark occurs replace the ignition module Ignition Module Removal Disconnect the high tension lead from the spark plug Disconnect the short circuit wire at the ignition module Remove the ignition module retaining screws and with draw the module from the saw Ignition Module Installation Install the ignition module but do not tight...

Page 20: ...rom the module to the spark plug If necessary cut the high tension lead to the correct length Using the assembly pliers P N 5025006 01 make a hole for the contact spring approximately 13 mm 1 2 in from the end of the lead Push the high tension lead through the spark plug boot until the lead extends out the other side Install the contact spring onto the end of the high tension lead with the assembl...

Page 21: ... Make sure that the piston stop is threaded completely into the cylinder Gently rotate the flywheel counterclockwise by hand until the piston contacts the piston stop Remove the flywheel retaining nut and washer The flywheel nut has right handed threads Thread the flywheel remounting device P N 5052679 12 onto the end of the crankshaft After the tool contacts the flywheel unthread the tool 1 1 2 t...

Page 22: ...wls are exposed Drive out the pawl retaining pins with a suitable drift Inspect the starter pawls and springs Replace components if necessary Reassemble the pawls and springs in the reverse order of disassembly Press the pawl retaining pins into the flywheel Make sure that the shoulder on the pins are flush against the flywheel surface and that the pawls pivot freely Flywheel Installation Thorough...

Page 23: ...on timing NOTE From serial number 9250857 the flywheel key is cast into the flywheel Install the flywheel and tighten the flywheel retaining nut to 25 30 Nm 18 4 22 1 ft lbs torque Check the air gap between the flywheel magnets and the ignition module as instructed in the Ignition Module section ...

Page 24: ...ure that the piston stop is threaded completely into the cylinder Rotate the clutch clockwise by hand until the piston contacts the piston stop The clutch hub has left hand threads Loosen the clutch hub in a clockwise direction and remove the clutch Slide the clutch drum with drive sprocket needle bearing and washer from the crankshaft Clean the parts ...

Page 25: ...tch shoes for wear by measuring the material thickness at the shoes thinnest point If the shoe is worn to less than 1 mm 0 040 in of material at the most worn part the shoes must be exchanged NOTE When exchanging clutch shoes always exchange all shoes at the same time Inspect the clutch hub spokes for wear Excessive wear causes a jarring sound and poor clutch operation ...

Page 26: ... worn rim or spur sprocket will cause premature wear of a new chain Exchange any questionable components Assembly Assemble the centrifugal clutch spring by hooking the ends together Position the hooked ends of the spring in the middle of a shoe then fit the shoe and spring to the clutch hub Secure the clutch hub in a vise With the assistance of a screwdriver and a pair of pliers lock the remaining...

Page 27: ...washer needle bearing and clutch drum onto the crankshaft Install the clutch hub and shoes Tighten the clutch hub to 30 40 Nm 22 1 29 5 ft Ibs WARNING Never start the saw without the bar chain and chain brake installed Due to the rapid acceleration and deceleration of the engine the clutch could come loose and cause severe injuries ...

Page 28: ...is located at the top and to the front of the bar pad Air should readily pass through the vent Remove the clutch assembly as instructed in section 7 Centrifugal Clutch Remove the oil pump cover pIate retaining screw and withdraw the cover plate Remove the oil pump assembly from the crankcase Using a screwdriver carefully remove the oil suction tube and filter Clean the oil pick up filter ...

Page 29: ...e oil pump components Exchange worn or damaged parts Assembly Thread the oil pump drive gear into the sleeve P N 502 5099 01 until the end of the gear is flush with the end of the sleeve Assemble the puller P N 5025026 01 to the sleeve without the center bolt Using a brass or plastic faced mallet drive the gear onto the crankshaft ...

Page 30: ...rankshaft install the oil suction tube and filter in the oil tank Slip the pump piston into the pump housing Fill pump cylinder with grease and slide the cylinder the piston the onto Fit the cylinder into pump housing with the notch in the cylinder towards the back side of the housing ...

Page 31: ...e ensuring that the pump piston and the pump cylinder engage the corresponding pin and notch in the crank case Fit the rubber grommet around the oil discharge port in the pump cylinder Install the oil pump cover plate and retaining screw Assemble the clutch as instructed in section 7 Centrifugal Clutch ...

Page 32: ...should be checked prior to each days use and exchanged as soon as any damage to the elements occur NOTE All rubber elements should be exchanged at the same time Checking the Rubber Elements If there seems to be excessive movement between the handles and the engine bar and chain assembly the rubber elements must be replaced Changing the Rubber Elements Disassembly Four rubber elements are used two ...

Page 33: ...Use a screwdriver to remove the rubber elements ...

Page 34: ...n If the vent fails the previously described test requiring vent servicing future fuel tank ventilation problems may be prevented by ensuring that the operator is follow ing the recommended fuel mix instructions in the Operator s Manual supplied with the saw Disassembly The fuel tank vent is located on the right side of the fuel tank next to the right rear rubber element With the fuel tank empty a...

Page 35: ...in Carburetor Removal Remove the air filter and disconnect the fuel hose at the carburetor Remove the one screw retaining the air filter mounting plate to the crankcase and the two screws retaining the plate and carburetor to the intake manifold Remove the air filter plate and carburetor with throttle linkage and if equipped choke linkage Remove the two screws retaining the intake manifold to the ...

Page 36: ...uel chamber and the diaphragm type fuel pump with the inlet and outlet check valves The fuel pump draws the fuel from the tank to the fuel chamber then pushes the fuel on to the metering section Disassembly NOTE The internal passages of the carburetor body are delicate and are easily damaged if proper service procedures are not used Damage to the fuel passages and seats is not repairable and will ...

Page 37: ...age is observed remove the screw retaining inlet lever pivot shaft and carefully remove the lever shaft spring and needle valve Check the needle valve Replace a damaged or worn needle valve necessitate the installation of a new carburetor Make sure the work area is clean and exercise extreme care during disassembly cleaning and reassembly of the carburetor Remove the screws retaining the metering ...

Page 38: ...10 Remove the one screw retaining the fuel pump cover and remove the cover Carefully remove the fuel pump diaphragm gasket and fuel pump diaphragm Using a pick carefully remove the fuel inlet screen ...

Page 39: ... damaged If the carburetor is very dirty it will be necessary to clean the fuel passages located underneath the fuel circuit plate Walbro WA or the welch plug s Walbro WT To remove a welch plug very carefully punch a hole through the center of the plug Pry the plug sideways to remove the plug from its seat ...

Page 40: ...nd channels with low pressure compressed air Check the throttle and if equipped choke valves and shafts for wear and exchange if necessary Assembly New gaskets diaphragms fuel inlet screen and welch plugs must be used to ensure correct carburetor function ...

Page 41: ...let lever Correct lever adjustment is critical An incorrect lever setting will cause erratic engine operation On Walbro WA carburetors the tip should be flush with the fuel chamber floor On Walbro WT carburetors the lever tip should be flush with the raised casting next to the lever on the fuel chamber floor Install the metering diaphragm gasket against the carburetor body first followed by the me...

Page 42: ...st the carburetor body first followed by the gasket and cover After assembly pressure test the carburetor for air leaks Pressure test at 50 kPa 7 2 psi No air leaks are permitted On carburetors equipped with choke valves check that the levers of the fast idle system are not worn and that they have positive engagement ...

Page 43: ...ensure that it is open and clean Check the pulse passage seal and rubber intake tube on the cylinder Exchange the seal and tube if the material has hardened or is damaged Apply a very thin coat of grease around the tip of the pulse passage tube on the manifold and install the manifold ...

Page 44: ...is installed correctly Tighten the retaining screws evenly Install the air filter plate to crankcase retaining screw The remainder of installation is the reverse of removal Changing the Fuel Filter The fuel filter is changed through the fuel filler opening using tool P N 5025083 01 After changing the filter make sure the external length of the fuel hose between the fuel tank and the carburetor is ...

Page 45: ...running adjustment first make a basic adjustment of the L and H mixture screws Rotate the L and H mixture screws in clockwise until lightly seated NOTE Damage to the mixture screw tips and tip seats may result if the screws are over tightened Now open counterclockwise rotation each mixture screw one full turn Final Adjustment NOTE A suitable two stroke single cylinder tachometer such as the one su...

Page 46: ...nd rich drop off settings then open 1 4 turn Adjust the idle speed to 2500 2800 rpm with the T screw again if necessary then recheck the L screw adjustment as previously described max rpm 12 000 With the low speed mixture adjusted the high speed mixture screw H is ready for adjustment Run the engine at wide open throttle while observing the tachometer Adjust the H screw so that the maximum no load...

Page 47: ...arburetor C Floods engine when not running Idle Low speed D Will not idle E Rich idle F Idles with needle closed G Erratic idle H L needle needs frequent adjustment J Loads up while idling Acceleration deceleration K Will not accelerate L Engine stops when closing throttle M Over rich acceleration High Speed N Will not run at full throttle O Low power P Will not 4 cycle No rich drop off ...

Page 48: ...e manifold gasket Loose carb mounting bolts Worn throttle assembly Incorrect throttle assembly Loose throttle valve screw Throttle shaft too tight 19 B t throttle linkage Metering System 37 Hole in diaphragm 20 Defective throttle 26 27 28 29 30 31 32 33 34 35 36 Worn lever Set too high Set too low Not free Distorted Improperly installed Leaking air fuel Worn button Improper assembly Defective gask...

Page 49: ...haust system be equipped with a spark arrester screen Check the screen and clean or exchange it if necessary A clogged or even partially clogged spark arrester screen will cause poor engine performance and overheating resulting in potential piston an cylinder damage ...

Page 50: ... Fuel System Remove the spark plug and the exhaust system Remove the four screws retaining the cylinder to the crankcase with the 8 mm T handle wrench P N 5025022 01 Carefully lift the cylinder straight up off the crankcase and piston Cover the crankcase opening with a clean cloth wrapped around the connecting rod Remove the piston pin retaining clips and push the pin out Separate the piston from ...

Page 51: ...marks Carefully grind the damaged spot with a fine file or a emery cloth Before the piston is reassembled the cylinder should be grinded as above When deeper scratches occur the piston should be exchanged and also the cylinder if necessary The piston ring is stuck in its Loosen the piston ring carefully groove and clean the groove very carefully before reassembly Check the piston ring for wear by ...

Page 52: ...ton and piston ring with oil A pin is located within the piston ring groove on the intake side of the piston to prevent ring rotation Make sure the ends of the piston ring are on either side of the piston ring retaining pin Using the piston cylinder mounting set P N 5025070 01 compress the piston ring with the appropriate ring compressor Carefully install the cylinder over the piston and ring Tigh...

Page 53: ...nition System and the oil pump as instructed in section 8 Chain Lubrication System The seals can be pried out using a suitable screwdriver Be careful not to scratch or damage the crankshaft during seal removal Always use new crankshaft seals for assembly Begin with the ignition side Apply grease to the crankshaft seal lip and carefully slide the seal over the end of the crank shaft The open side o...

Page 54: ...se halves by pressing the crankshaft out of the right crank case half Mount the tool on the left crankcase half and press out the crankshaft Remove the crankshaft bearings from the crankcase halves by heating up the crankcase around the crank shaft bearing then pressing the bearing out of the case ...

Page 55: ...arefully inspect the connecting rod big end crank pin bearing Hold the connecting rod flush against one crank half and then the other while rotating the rod around the pin Look for cracks or other damage to the bearing cage Examine the connecting rod big end for seizure marks on the sides or discoloration Check for radial movement up and down play of the connecting rod Replace the crankshaft if ra...

Page 56: ...ts before assembly Make sure the crankcase half mating surfaces are clean and free of all gasket material Heat the bearing seat area of the ignition right side crankcase half and install the crank shaft bearing Make sure the bearing is fully seated Heat the bearing seat area of the drive left side crank case half and install the crankshaft bearing ensuring it is fully seated ...

Page 57: ...case half Slide the drive side crankcase half onto the crankshaft then mount the assembly tool Pull the crankshaft into the crankcase half while guiding the two halves together If necessary starl a few crankcase screws to hold the gasket in place Make sure the crankshaft is flush against the bearing then remove the assembly tool Install all the crankcase screws except the top front screw which als...

Page 58: ...nd of the crankshaft The open side of the seal must face inward Drive the seal into the crankcase using tool P N 5025079 01 until the seal is flush with the crankcase Install the drive side crankshaft seal in the same manner The remainder of reassembly is the reverse of disassembly Refer to the appropriate sections for reassembly instructions ...

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Husqvarna 50 Rancher, Workshop Manual

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Summary of Contents for 50 Rancher

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