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STIHL 020 T

1. 4 3 Oil Seals It is not necessary to disassemble the complete crankcase if only the oil seals have to be replaced Clutch side e Remove the oil pump see 9 3 1 e Rotate the angled ends on the hooks 1 of the puller 3 so that they are in line with the arms 2 e Apply the puller rotate hooks 90 angled ends must locate under the oil seal Clamp the arms and pull the oil seal out Important Take special care not to damage crankshaft stub e Clean sealing face on crankshaft stub with standard commercial solvent based degreasant con taining no chlorinated or halogen ated hydrocarbons see 11 2 e Pack cavity between sealing lip and oil seal with grease see 11 2 STIHL 020 T Push the oil seal closed side facing crankcase over the crankshaft and use press sleeve 1 to press it home Install the oil pump see 9 3 1 Ignition side e Remove the flywheel see 5 5 Apply the puller as at the clutch side and pull out the oil seal Important Take special care not to damage crankshaft stub e Clean sealing face on crankshaft stub with standard commercial solvent based degreasant contai ning no chlorinated or halogena ted hydrocarbons see 11 2 e Pack cavity between sealing lip and oil seal with grease see 11 2 Slip the installing sleeve 1 over the crankshaft The slot must locate on the Woodruff key 2 e Push the oi
2. ment in a fresh non flammable cleaning solution e g warm soapy water and if possible blow out with compressed air Soften encrusted dirt by soaking the parts in cleaning solution Important Flocked air filters must not be cleaned with compressed air brushes or cloths Note If filter is damaged install new part immediately Installation is a reversal of the removal sequence Push the fuel hose off the elbow connector Disconnect the choke rod from the choke shaft e Pull the carburetor off the studs and detach the throttle rod 1 from the throttle shaft 2 at the same time Installation is a reversal of the removal sequence Note Check that sleeve in manifold and washer are in place before fitting the carburetor Fit new mounting nuts and tighten them down to 3 3 Nm 2 4 Ibf ft STIHL 020 T 10 2 2 Leakage Testing The carburetor can be tested for leaks with the carburetor and crankcase tester 1 Remove the carburetor see 10 2 1 Use fuel line 2 with nipple 3 as adapter to make connection bet ween tester and carburetor s elbow connector Push the nipple into the tester s pres sure hose Close the vent screw 4 on the rubber bulb and pump air into the carburetor until the pressure gauge shows a reading of approx 0 4 bar 5 8 psi If this pressure remains constant the carburetor is airtight However if it
3. Installing the new rope bush e Place the new bush in its seat in the fan housing e Check that washer is fitted on starter post Install the spring clip see 6 2 e Refit the fan housing STIHL 020 T e Fit the thrust sleeve 1 tapered end first and the hexagon nut e Tighten down the hexagon nut until the bush is firmly seated Note The installing tool flares the lower end of the rope bush e Remove the installing tool Thread the starter rope through the guide bush from outside and fit it on the rope rotor see 6 3 e Refit the rope rotor see 6 2 e Refit the fan housing 38 7 AV HANDLE SYSTEM The crankcase and tank housing e Tighten lower screws to 5 5 Nm are connected by vibration damping 4 Ibf ft and center screw to rubber buffers Damaged rubber 4 Nm 3 Ibf ft buffers annular buffers must always be replaced in sets e Fit the handle molding see 8 2 Front upper annular buffer e Fit the chain sprocket cover see 3 2 e Remove the chain sprocket cover see 3 1 Front lower annular buffer e Remove the handle molding e Remove the fan housing see 8 2 see 6 2 Rear annular buffer e Pull terminal off the spark plug see 3 1 e Take out the screws 1 and 2 e Remove the center screw e Remove front handle mounting Remove the annular buffer screw from annular buffer e Place annular buffer in position Tighten lower screws to 1 7 Nm 1 25 Ibf ft and
4. Take out the pump piston 5 with spring 6 and washers 7 Wash all parts in white spirit Inspect the parts for damage and replace as necessary Assembly is a reversal of the disassembly sequence Note Always install new 0 rings Lubricate pump piston and worm with grease see 11 2 before installing 46 10 FUEL SYSTEM 10 1 Air Filter Carburetor Removina and Installina 10 2 10 2 1 Dirty and clogged air filters reduce engine power increase fuel con sumption and make starting more difficult The air filter should always be cleaned when engine power begins to drop off e Before removing the filter close the choke shutter to prevent dirt falling into the carburetor press down interlock lever 1 and move Master Control lever 2 all the way back to the cold start position e Rotate twist lock 1 on carburetor box cover 2 one quarter turn counterclockwise and remove the cover STIHL 020 T e Clean away any loose dirt from Troubleshooting chart see 2 6 around the filter Remove the air filter see 10 1 e Remove the air filter Unscrew the carburetor mounting nuts 1 e Remove the filter base 2 Ease the grommet off the adjusting screws and pull it out of the handle housing Take the foam element out of the filter base e Wash the air filter and foam ele
5. Aids Special Servicing Tools No 1 Locking strip for piston 2 Press sleeve 3 Assembly sleeve 4 Assembly hook 5 Assembly tube 6 Assembly drift 7 Clamping strap 8 Wooden assembly block 9 Carburetor and crankcase tester 10 Vacuum pump 11 Nipple 12 Fuel line 16 Sealing plate 17 Test flange 18 Setting gauge 13 Flange 14 Pin 15 Pan hd screws 19 Stud puller M8 20 Installing tool 9 21 Puller 22 Service tool AS set 23 Threaded sleeve 24 Screwdriver bit T27x125 25 Socket 13 mm 26 Torque wrench 27 Torque wrench 28 Assembly tool 29 Installing tool 30 Assembly hook 31 Screwdriver T20x100 32 T handle screwdriver Q SW 8x200 33 Crimping tool 34 Assembly stand 35 Screwdriver T27x150 36 Puller 37 Jaws 38 Socket T20x125 Remarks 0000 893 5903 1129 893 2400 1129 893 4600 5910 890 2800 1117 890 0900 1114 893 4700 0000 893 2600 1108 893 4800 1106 850 2905 0000 850 3501 0000 855 9200 1110 141 8600 0000 855 8106 1128 850 4200 1111 890 6400 1123 850 4200 0000 963 1008 9043 319 8100 5910 893 0501 5910 890 2209 1116 893 0800 5910 007 2205 5910 893 2407 0812 542 2104 5910 893 5608 5910 890 0301 5910 890 0302 5910 890 0311 5910 890 0312 1116 893 4800 0000 890 2201 5910 893 8800 5910 890 2301 5910 890 2420 5910 890 8210 5910 850 3100 5910 890 2302 0000 890 4400 0000 890 3700 0812 542 2041 Blocking the crankshaft Installing oil seal and roller bearing in crankcase Protecting oil
6. Normal Sooted Smeared with oil Overheated STIHL 020 T Grayish yellow to brown dry Velvet like dull black coating of soot Coating of damp oil carbon and soot Welding beads on insulator nose pitted electrodes Meaning Engine in order correct spark plug heat range as specified Mixture too rich lack of air dirty air filter choke shutter partly closed electrode gap too wide wrong spark plug heat range too high Too much oil in fuel mix Mixture too lean spark plug loose wrong spark plug heat range too low 30 5 2 Ignition Plug Terminal Coat end of the ignition lead about 20 mm 3 4 with oil e Fit spark plug terminal over the ignition lead e Use suitable pliers to grip the end of the ignition lead inside the spark plug terminal and pull it out e Remove the chain sprocket cover e Pull terminal 1 off the spark plug 2 e Use a suitable pair of pliers to grip the leg spring and pull it out of the spark plug terminal e Pinch the hook of the leg spring into the center of the lead i e about 15 mm from the end of the lead e Pull the lead back into the terminal so that the leg spring locates properly inside it e Unhook the leg spring from the ignition lead e Slip the spark plug terminal off the lead e Fit terminal on spark plug and refit chain sprocket cover STIHL 020 T 5 3 Ignition Lead e Remove the ignition module se
7. crankcase 7 0 5 2 2 Spline screw IS M 5x16 Cylinder 11 5 8 5 Nut M5 Carburetor 3 3 2 5 Collar nut M 8x1 Flywheel 25 0 18 5 Collar nut M 8x1 L Clutch 32 5 24 0 M 14x1 25 Spark plug 25 0 18 5 Screw assembly IS P 5 Annular buffer handle housing 4 0 3 0 1 Spline screw IS M 4x16 Annular buffer front 5 5 4 0 Spline screw IS P 4x14 Annular buffer rear 1 7 1 25 1 Screw IS P 6x21 5 Front handle handle housing 5 5 4 0 1 Screw IS P 4x10 Control lever switch shaft 1 3 0 95 1 Use the following procedure when refitting a P or DG screw in an existing thread Place the screw in the hole and rotate it counterclockwise until it drops down slightly Tighten the screw clockwise to the specified torque This procedure ensures that the screw engages properly in the existing thread and does not form a new thread 1 Torque may be reduced by approx 1 Nm 0 7 Ibf ft when refitting a screw in an existing thread 2 Screw must be secured with adhesive 0786 111 1101 Loctite 243 3 A washer must be fitted under the screw head Note Screws secured with adhesive are easier to release if the adhesive is heated first with a hot air blower hair dryer Exercise caution on polymer components STIHL 020 T 2 TROUBLESHOOTING CHARTS 2 1 Clutch Chain Drive Chain Brake and Chain Tensioner Condition Cause Remedy Saw chain turns at idle speed Engine speed too high Spring hooks broken Readjust at idle speed adjusting screw c
8. during this process to ensure that no jolts are transmitted to the connecting rod e Remove piston and take the needle cage out of the connecting rod V Ame e Inspect piston rings and replace if necessary see 4 5 4 4 2 Installation e Thoroughly clean the gasket e Fit the piston pin 1 on the e Push the large slotted diameter seating surface 1 assembly drift 2 and slide it into of the sleeve over the magnet the piston the pin slides home and snap ring Position the e Lubricate the needle cage 2 with easily if the piston is hot sleeve so that the inner pin 1 oil and fit it in the small end points towards the flat face 2 of tool s shank A e Heat the piston on an electric Note Use the installing tool 1 to fit Stand the installing tool sleeve heating plate to approx 60 C the snap rings downward on a flat surface 140 F and slip it over the wooden board and press verti connecting rod The arrow 1 the e Remove the sleeve 2 from the cally downwards until the sleeve piston head must point to the right tool butts against the tool s shoulder looking at flywheel 2 e Push the assembly drift small e Attach the snap ring 1 to the e Remove the sleeve and slip it onto diameter first through the piston magnet 2 so that the snap ring the other end of the shank and small end needle cage and gap is on the flat side of the tool s line up the piston shank see illustr
9. housing Equalization of pressure from the outside inwards takes place via the filter element 1 and the valve 2 If pressure builds up in the tank the valve closes and excess pressure is dissipated via the carburetor Use suitable tool to remove filter element Note Remove handle housing if necessary see 8 8 STIHL 020 T Remove the exhaust muffler see 4 1 Note Press in valve as far as stop Use a screwdriver to carefully raise the rear of the handle housing slightly Position filter element in the bore and press it home as far as stop Remove cover from manifold e Remove upper screws from tank housing 55 e Remove screws from underside e Unscrew filler cap and push cord e Pry the flange of the fuel hose of tank housing 1 out of groove 2 out of the tank and lift it away e Pull tank housing slightly Remove filter element 1 and e Take out the insulating plate 1 forwards disconnect impulse valve 2 of tank vent hose from nipple and then Reassemble and install in the remove tank housing reverse sequence Note Bond a new heat reflecting foil 2 in the new tank housing e Pull out the impusle hose 1 e Pull the pickup body off the fuel and grommet 2 Take out screws hose 3 and 4 Remove annular buffer 5 and retainer 6 STIHL 020 T 56 11 11 1 Special Servicing Tools and
10. removing it Cleaning the fuel tank e Unscrew the filler cap and drain the tank Pour a small amount of clean gasoline into the tank e Close the tank and shake the saw vigorously e Open the tank again and drain it STIHL 020 T Push the fuel intake hose off the elbow connector e Pull the pickup body off the fuel hose Install in the reverse sequence Fuel intake hose Remove the air filter see 10 1 e Unscrew the carburetor mounting nuts 1 e Remove the filter base 2 e Pull off the pickup body e Pry the fuel hose out of the fuel tank and lift it away Install in the reverse sequence Note Coat the hose flange 1 with a little oil to simplify installation The pointed tip of the flange must locate in the pointed recess 2 in the fuel tank 54 10 5 Tank Vent Correct operation of the carburetor is only possible if atmospheric pressure and internal fuel tank pressure are equal at all times This is ensured by the tank vent Important In the event of trouble with the carburetor or the fuel supply system always check and clean the tank vent 10 6 Tank Housing e Remove the handle housing see 8 8 e Unscrew the tank filler cap e Pull the valve out of its seat in the tank e Take out fan housing mounting screws Install in the reverse sequence e Remove the fan
11. seal at ignition side Detaching springs from clutch shoes Attaching the brake spring Fitting piston pin Compressing piston rings Fitting piston Testing carburetor and crankcase for leaks Testing crankcase for leaks Sealing exhaust port for leakage test For leakage test Setting air gap between ignition module and flywheel Removing bar mounting stud Fitting hookless snap rings in piston Removing flywheel Separating crankcase halves For IS screws 5 mm Crankshaft nut ign end and clutch Screw assemblies 0 5 to 18 Nm Screw assemblies 6 to 80 Nm DO DN Yee a Installing rewind spring Flaring rope guide bush Removing pickup body For all IS P screws 4 mm Carburetor nuts Attaching connectors to electrical wires Holding saw for repairs For all IS screws 5 mm Removing oil seals Tightening IS P screws 4 mm 1 Plastoform and DG screws must always be tightened with torque wrench 2 Wrench has optical acoustic signal STIHL 020 T 57 11 2 No 10 Servicing Aids Lubricating grease 0781 120 1111 STIHL multipurpose grease 0781 120 1109 80 g 2 3 4 oz tube High strength 0786 111 1109 threadlocking Loctite 270 Threadlocking adhesive Loctite 243 Standard commercial solvent based degreasant without chlorinated or halogenated hydrocarbons STIHL special lubricant 0781 417 1315 Ignition lead HTR 10 m 33 0000 930 2251 Electrician s repair kit 0000 007 1013 Graph
12. 0 04 below the housing face e Push pickup body 1 through the hole and locate the flange 2 on the suction hose in the hole f n j are E DA O e igor Q e Place bumper strips in position and press them home as far as they will go Nri a Ae Thread ignition lead through the hole e Fit the spiked bumper 1 e Tighten the screws 2 firmly e Use press sleeve 2 to press roller bearing 1 as far as stop into clutch side of crankcase Lubricate bearing with oil 27 e Use press sleeve 2 to press roller bearing 1 as far as stop into ignition side of crankcase e Lubricate bearing with oil Fit the straight stub of the crank shaft in the roller bearing at the clutch side of the crankcase e Fit new gasket on mating face of clutch side of crankcase STIHL 020 T oT 1 lt e Push ignition lead 1 through the grommet 2 ers e Lubricate roller bearing in ignition side of crankcase with oil and push the crankcase over the crankshaft stub e Fit screws and tighten down alternately in a diagonal pattern to 5 5 Nm 4 Ibf ft Note Trim away any excess gasket material in the area of the cylinder mounting face e Fit Woodruff key in the slot in the crankshaft stub e Before installing oil seals coat sealing lips with grease see 11 2 Slide the oil seal closed side facing the crankcase over the clutch end of the
13. 50 1129 007 1000 STIHL 020 T 1 6 Tightening Torques Plastoform screws are used for polymer components and DG screws for lightmetal components These screws form a permanent thread when they are installed for the first time They can be removed and installed as often as necessary without detrimentally affecting the strength of the screwed assembly providing the specified tightening torque is observed For this reason it is essential to use a torque wrench Fastener Thread size For component Torque Remarks Nm Ibf ft Spline screw IS P 4x14 Chain catcher 1 7 1 25 1 Spline screw IS P 4x14 Insert chain brake 3 2 2 4 1 Spline screw IS P 4x14 Handle molding 1 6 1 2 1 Spline screw IS DG 4x15 Muffler 4 0 3 0 Spline screw IS M 5x12 Spiked bumper crankcase 7 0 5 2 Spline screw IS M 5x20 Muffler to cylinder 11 5 8 5 2 Spline screw IS DG 4x15 Insert 3 2 2 4 Spline screw IS M 4x12 Oil pump 3 5 2 6 Spline screw IS M 5x12 Annular buffer front handle 6 0 4 4 Spline screw IS P 6x19 Ring on housing 7 0 5 2 1 Spline screw IS P 5x20 Fan cover tank housing 4 0 3 0 1 Spline screw IS M 4x16 Fan cover crankcase 4 0 3 0 Spline screw IS P 4x10 Segment fan cover 3 2 2 4 1 Spline screw IS M 4x12 Cover chain tensioner 2 4 1 8 Spline screw IS M 4x12 Cover oil pump 3 0 2 2 Spline screw IS M 4x16 Crankcase 5 5 4 0 Spline screw IS M 4x16 Tank housing 5 3 3 9 Spline screw IS M 4x20 Ignition module 6 5 4 8 2 3 Spline screw IS M 5x12 Bar mounting flange
14. 6 1 6 2 6 3 6 4 6 5 6 6 6 7 8 1 8 2 8 3 8 4 8 5 8 6 8 7 8 8 9 1 9 2 9 3 9 3 1 9 3 2 Ignition System Spark Plug Spark Plug Terminal Ignition Lead Ignition Module Ignition Timing Removing and Installing Flywheel Ground Wire Short Circuit Wire Rewind Starter Routine Maintenance Rope Rotor Replacing the Starter Rope Replacing the Rewind Spring Tensioning the Rewind Spring Pawl Starter Rope Guide Bush AV Handle System Master Control Handle System Master Control Lever Choke Throttle Rods Interlock Lever Throttle Trigger Switch Shaft Contact Springs Double Lever Choke Throttle Front Handle Handle Housing Chain Lubrication Suction Hose Pickup Body Vent Valve Oil Pump Removing and Installing Servicing 29 29 31 31 32 32 33 33 34 35 35 35 36 36 37 38 38 39 40 40 40 41 41 41 42 42 43 44 44 45 46 46 46 10 10 1 10 2 10 2 1 10 2 2 10 2 3 10 3 10 4 10 5 10 6 11 Fuel System Air Filter Carburetor Removing and Installing Leakage Testing Servicing Carburetor Adjustment Pickup Body Fuel Hose Tank Vent Tank Housing Special Servicing Tools and Aids Special Servicing Tools Servicing Aids 47 47 47 47 48 48 53 54 55 55 57 57 58 1 SPECIFICATIONS 1 1 Engine 1 2 Fuel System STIHL 020 T STIHL single cylinder two stroke engine with special impregnated cy
15. Service Manual 020 T Chain Saws This manual contains detailed descriptions of all repair and servicing procedures for 020 T chain saws You should make use of the illustrated parts list while carrying out repair work It shows the installed positions of the individual components and assemblies Microfilmed parts lists are always more up to date than printed lists A fault on the machine may have several causes Consult the Troubleshooting Charts when tracing faults Refer to the Technical Information bulletins for engineering changes which have been introduced since publication of this service manual Technical information bulletins also supplement the parts list until a re vised edition is issued The special servicing tools mentioned in the descriptions are listed in the last chapter of this manual Use the part numbers to identify the tools in the STIHL Special Tools manual The manual lists all special servicing tools currently available from STIHL Service manuals and all technical information bulletins describing engineering changes are intended exclusively for the use of STIHL servicing dealers They must not be passed to third parties STIHL 020 T Always use original STIHL replacement parts They can be identified by the STIHL part number the EA a STIHL o0 and the STIHL parts symbol amp 1 The symbol may appear alone on a small parts lt Servicing and repairs are made cons
16. am element 1 3 Ignition System Type Air gap Ignition timing Advance angle Spark plug Suppressed Electrode gap Electronic magneto ignition breakerless with integral trigger unit 0 25 mm 0 010 in 2 0 2 8 mm B T D C at 8 000 r p m 24 7 32 5 B T D C at 8 000 r p m Bosch WSR 6 F or NGK BPMR7 A 0 5 mm 0 020 in Spark plug thread M14x1 25 Length of thread 9 5 mm 0 37 in Heat range 200 1 4 Cutting Attachment Guide bars Rollomatic Bar tail 3005 Bar lengths 30 35 40 and 45 cm Oilomatic chain Chain sprockets Chain speed Chain lubrication Oil feed rate adjustable Oil tank capacity 12 14 16 and 18 in 3 8 9 32 mm Picco Micro Optional 1 4 6 35 mm Rapid Micro 6 tooth spur sprocket for 3 8 Picco Optional 7 tooth for 3 8 Picco 8 tooth for 1 4 18 6 m s 61 ft sec at 10 000 r p m with 6 tooth 3 8 P sprocket Speed controlled reciprocating oil pump no oil feed at idle speed Additional manual oil flow adjustment 4 0 10 5 cm min 0 14 0 36 fl oz min at 10 000 r p m 0 24 I 0 5 US pt 1 5 Special Accessories 1 5 1 For User 1 5 2 For Service Shop STIHL repair kit 7 tooth 3 8 P spur sprocket 8 tooth 1 4 spur sprocket Elastostart Air filter flocked Carburetor parts kit Gasket kit Spur gear tensioning screw kit 1129 900 5000 1129 640 2050 1129 640 2051 1128 190 3400 1129 120 1606 1129 007 1060 1129 007 10
17. ation Note Inner pin must again point towards flat face of tool s shank STIHL 020 T 21 mf 2 4 i e Apply the installing tool to the piston boss hold the piston steady center the tool shank exactly and press home until the snap ring slips into the groove e Position the piston rings so that the radii at the ring gap meet at the fixing pin in the piston groove when the rings are compressed e Push the manifold onto the intake port Make sure that the straight faces see arrows on the manifold and port line up Note Fit the snap ring so that its gap is on the piston s vertical axis it must point either up or down e Fit new cylinder gasket e Use the clamping strap 1 to compress the piston rings e Lubricate piston and piston rings around the piston with oil Rest the piston 1 on the wooden assembly block 2 e Check that piston rings are correctly positioned STIHL 020 T e Lubricate the inside of the cylinder with oil and line it up so that it is positioned as it will be in the installed condition It is essential to observe this point as the piston rings might otherwise break e Slide the cylinder over the piston the clamping strap is pushed downward as the piston rings slip into the cylinder e Remove clamping strap and wooden assembly block e Carefully line up the cylinder gasket e Fit cylinder base screws and tighten them alternately to 11 5 Nm 8 5 Ibf ft i
18. ator nose with a grease solvent and blow it clear with compressed air Electrode gap Electrode gap becomes wider as a result of normal erosion Bend the ground electrode as necessary Important Always fit a new spark plug if the electrodes are badly eroded 29 Checking the spark plug Accurate checking of the spark plug is only possible with a special spark plug tester A provisional check can be carried out by fitting a clean spark plug in the spark plug terminal and holding it against ground There should be a powerful sparkover at the electrodes when the engine is cranked by pulling the starter rope Warning Do not touch any live parts contact with high voltage can cause serious or fatal accidents Note It is best to fit a new spark plug in all cases of doubt If there is no sparkover even though the spark plug is in good condition first check the connections Note Chafed insulation on the ignition lead or short circuit wire will cause a short circuit to ground In this case the engine with either not start or only run erratically To install the spark plug Clean the spark plug seat and inspect the sealing ring to make sure it is in good condition Fit the spark plug and tighten it down to 25 Nm 18 5 Ibf ft The appearance of the spark plug s insulator nose gives valuable information with regard to the effects of various operating conditions Condition of insulator nose
19. center screw to 4 Nm 3 Ibf ft e Fit terminal on spark plug e Fit the chain sprocket cover e Take out the lower screws 1 e Unscrew the annular buffer and removeannular buffer 2 e Tighten front handle mounting e Note that ground wire 3 is screw to 6 Nm 4 4 Ibf ft secured with the lower rear screw e Refit the fan housing STIHL 020 T 39 8 MASTER CONTROI HANDLE SYSTEM 8 1 Master Control Lever 8 2 Choke Throttle Rods The thumb operated Master Control e Remove the Master Control lever e Disconnect throttle rod from lever moves the switch shaft to select see 8 1 double lever throttle the required function e Take out the screws The following positions can be selected with the Master Control e Remove the handle molding lever STOP short circuit contact closed ignition interrupted RUN normal operating position START warm start starting throttle choke shutter open CHOKE cold start starting throttle choke shutter closed e Pull out the retainer e Pull out double lever choke slightly swing choke rod 1 upwards and disconnect Assemble in the reverse sequence e Take out the screw 1 e Disconnect choke rod 1 from lever on switch shaft and throttle e Pull the lever 2 off the switch rod 2 from throttle trigger shaft STIHL 020 T 40 8 3 Interlock Lever 8 4 Switch Shaft 8 5 Contact Spring
20. cover 2 crankcase from inside the tank e Blow valve clear with compressed air from outside STIHL 020 T e Place vent valve in position with its smaller bore facing outwards e Use a 5 mm 0 2 drift to careful e Use a7 mm 0 3 drift to careful ly push home the valve until it is recessed about 1 mm 0 04 be low the housing face Fit the bumper strip e Fit the cover e Fit the chain sprocket see 3 3 Fit the oil tank filler cap 9 3 Oil Pump 9 3 1 Removing and Installing e Pull the worm off the crankshaft stub Pull suction hose off nipple on oil pump see 9 1 e Take out the oil pump mounting screws Ease oil pump peg 1 out of plug 2 and remove the oil pump e Remove the plug Install in the reverse sequence STIHL 020 T Note The ignition lead must be located in the crankcase recess behind the oil pump e Tighten down oil pump mounting screws to 3 5 Nm 2 6 Ibf ft Sa SG e Inspect the teeth 1 and bush 2 of the worm and replace worm if necessary Note The worm and chain sprok must always have the same number of teeth TR fea 2 9 3 2 Servicing Check suction hose and pickup body before disassembling the oil pump Remove the oil pump see 9 3 1 Drive out the roll pin 1 with a 2 mm 0 08 drift Pull out the adjusting screw 2 and remove the 0 rings 3 Remove the plug 4
21. crankshaft and use the press sleeve 1 to press it fully home e Fit the assembly sleeve 1 over the ignition end of the crankshaft Slide the oil seal 2 closed side facing the crankcase over the assembly sleeve bd gt Press home the oil seal with the press sleeve 1 Assembly of the remaining parts is a reversal of the disassembly sequence 28 5 IGNITION SYSTEM Warning Exercise extreme caution when carrying out maintenance and repair work on the ignition system The high voltages which occur can cause serious or even fatal accidents The electronic breakerless magneto ignition system basically consists of an ignition module 1 and flywheel 2 and is easily accessible STIHL 020 T 5 1 Spark Plug Troubleshooting on the ignition system should always begin at the spark plug In the event of starting difficulties low engine power misfiring etc unscrew the spark plug and check that it is the approved type Only the spark plugs listed in the specifications may be used Other makes of spark plug are unsuitable because they have longreach electrodes Check the electrode gap at 4 regular intervals with a feeler Sooted or carbonized spark gauge It should be 0 5 mm plug 0 02 e Use brass wire brush to clean the spark plug and then blow it clear with compressed air Note Never use a steel wire brush for this job Spark plug smeared with oil e Wash the insul
22. d ports Clean pickup body fit new filter Clean fuel strainers See also 2 2 STIHL 020 T 11 3 CLUTCH CHAIN DRIVE CHAIN BRAKE AND CHAIN TENSIONER 3 1 Disassembling Clutch 3 2 Assembling Clutch Troubleshooting chart see 2 1 e Unscrew the clutch from the e Slip the retainers 1 onto the stub of the crankshaft clutch shoes 2 so that the e Disengage the chain brake by narrow side is next to the series pulling the hand guard toward Caution Clutch has a left hand number e g 1129 3 the front handle thread e Unscrew collar nut 1 and remove the sprocket cover 1 e Pull terminal 1 off the spark plug e Use assembly hook 2 to remove Fit the clutch shoes over the arms 2 Unscrew the spark plug all the clutch springs 1 1 of the clutch carrier so that the series number is on the same side e Pull the clutch shoes off the as the larger hexagon 2 carrier e Pull the retainers off the clutch shoes e Clean all parts and stub of crankshaft in white spirit Replace any damaged or worn parts e Set piston to bottom dead center e Clamp the clutch e g one shoe in a vise e Push the locking strip 1 thicker end 2 first into spark plug hole and then rotate it 180 STIHL 020 T 12 Attach one end of each spring 1 to the clutch shoes e Use the assembly hook 2 to attach the other ends of the springs and press them firmly into the clutch shoes with on
23. d setting Turn idle speed stop screw LA clockwise until the chain begins to run then turn it back one quarter turn Chain runs while engine is idling Check standard setting Turn the idle speed stop screw LA counterclockwise until the chain stops running and then turn it about another quarter turn in the same direction Erratic idling behavior poor acceleration Idle setting too lean Turn the low speed adjusting screw L counter clockwise until the engine runs and accelerates smoothly Exhaust smokes at idle speed Idle setting too rich Turn the low speed adjusting screw L clockwise until the engine speed drops and then turn it back one quarter turn and check that the engine accelerates smoothly when the throttle is opened 53 10 4 Pickup Body Fuel Hose The diaphragm pump draws fuel out of the tank and into the carburetor via the fuel hose Any impurities mixed with the fuel are retained by the pickup body filter The fine pores of the filter eventually become clogged with minute particles of dirt This restricts the passage of fuel and results in fuel starvation Important In the event of trouble with the fuel supply system always check the fuel tank and the pickup body first Clean the fuel tank if necessary Pickup body e Use the assembly hook 1 to pull the pickup body out through the fuel tank filler opening Note Do not stretch the fuel hose while
24. drops there are two possible causes 1 The inlet needle is not sealing foreign matter in valve seat or sealing cone of inlet needle is damaged or inlet control lever sticking 2 The metering diaphragm is damaged In either case the carburetor must be removed and serviced After completing test open the vent screw and pull the fuel line off the elbow connector Install the carburetor see 10 2 1 10 2 3 Servicing e Remove the carburetor see 10 2 1 Unscrew and remove the fuel pump end cover e Remove the gasket and pump diaphragm from the cover or carburetor body Note The diaphragm and gasket often stick to the cover or carburetor body If this is the case take particular care when separating them 48 If the fuel strainer in the pump side of the carburetor body is dirty use a scriber to pry it out and then clean it Important If the fuel strainer is damaged fit a new one In such a case the fuel pickup body should also be inspected and replaced if necessary see 10 4 e Take out the screws of the metering chamber end cover and lift away the cover STIHL 020 T e Remove the metering diaphragm and gasket from the carburetor body or the cover e Remove the round head screw 1 e Remove the inlet control lever 2 with spindle 3 helical spring 4 and inlet needle 5 s
25. drops of STIHL special lubricant before installation see 11 2 e The retainer 1 slips off as the rewind spring is pressed into the fan housing Engage the anchor loop 2 over the lug in the fan housing Caution The rewind spring can pop out and uncoil during installation e If the rewind spring has popped out it must be refitted as follows e Tie one of the special knots shown and pull the rope back into the starter grip e Install the rope rotor see 6 2 e Position anchor loop about a 11 mm 0 4 from the edge of the assembly tool 1 36 6 5 Tensioning the Rewind Spring e Fit the rewind spring in the assembly tool in the counter clockwise direction starting outside and working inwards e Make a loop in the starter rope Note The wooden assembly block can be placed over the assembly tool to simplify refitting Slip the assembly tool with rewind spring over the starter post e Grip the rope close to the rotor and use it to turn the rope rotor seven full turns clockwise a amp e Push the rewind spring into the fan housing and then remove the assembly tool e Hold the rope rotor steady e Pull out the rope with the starter grip and straighten it out e Install the rope rotor see 6 2 STIHL 020 T e Hold the starter grip firmly to keep the rope tensioned e Let go of the rope rotor and slowly release the starter grip so that the rope wind
26. e finger 3 3 Chain Sprocket Remove clutch see 3 1 e Pull chain sprocket off the cranks haft 3 4 Disassembling Chain Brake e Remove sprocket cover see 3 1 Engage brake band by pushing the hand guard away from the sprocket cover e Screw clutch onto crankshaft and torque down to 32 5 Nm 24 Ibf ft e Remove locking strip from cylinder Install spark plug and torque down to 25 Nm 18 5 Ibf ft Refit terminal ii e Fit sprocket cover so that pin 1 A engages hole 2 Fit the collar nut STIHL 020 T Take the needle cage out of the sprocket e Clean stub of crankshaft Wash needle cage in clean white spirit and lubricate with grease see 11 2 Replace damaged needle cage e The chain sprocket must engage the worm properly e Install clutch see 3 2 e Take out screws 1 e Remove the segment 2 e Carefully pry the brake spring 1 off the anchor pin and unhook it from the bell crank 2 13 e Take the brake band 1 out of the sprocket cover and detach it from the bell crank 2 at the same time e e Ease the hand guard 1 and bell crank 2 off the pivot pins e Pull the bell crank out of the hand guard and then take the hand guard out of the sprocket cover lee e Remove lever 1 with pivot pin and flat spring 2 e Inspect parts Replace any worn or damaged parts STIHL 020 T 3 5 Assembling Chain Bra
27. e 5 4 2 e Remove the flywheel see 5 5 e Remove the oil pump see 9 3 1 e Pull terminal off spark plug e Pull ignition lead out of crankcase e Remove the spark plug terminal see 5 2 e Cut new ignition lead to length see parts list or cut to same length as old lead 31 5 4 Ignition Module lt Dee 1 Vo Nie f SS ot N ee N jj 2 XP a e Use a pointed tool awl or gimlet to pierce the center of the other end of the ignition lead which screws into the module L K e Pull out the groomet at the ignition side Starting from the clutch side thread the ignition lead 1 through the crankcase bores and the grommet 2 SS lene LA v HW e Fit the grommet in the bore Assembly of the remaining parts is a reversal of the disassembly sequence STIHL 020 T The ignition module accommodates all the components required to control ignition timing There are two electrical connections on the coil body 1 the high voltage output 2 the connector tag for the short circuit wire Accurate testing of the ignition module is only possible with sophisticated test equipment For this reason it is only necessary to carry out a spark test in the workshop A new ignition module must be installed if no ignition spark is obtained after checking that wiring and stop switch are in good condition 5 4 1 Ignition Timing Ignitio
28. e Carefully separate the diaphragm and gasket e Inspect diaphragms and replace if necessary Note The diaphragms are the most delicate parts of the carburetor They are subjected to continuous alternating stresses and the material eventually shows signs of fatigue i e the diaphragms distort and swell and have to be replaced The inlet needle valve is located in a recess in the metering diaphragm chamber e If there is an annular indentation on the sealing cone of the inlet needle it will be necessary to replace the inlet needle because it will no longer seal properly This is indicated by constant flooding of the carburetor even though the needle is clean Remove the carburetor adjusting screws 49 e Use a 4 5 mm 0 18 dia drift to press the valve jet out of its seat in the direction of the venturi and wash it in white spirit Remove the sealing plug from the metering chamber Caution The sealing plug is des troyed during removal It should therefore only be re moved if a replacement is available e Wash the carburetor body and all parts in fresh white spirit and blow clear with compressed air paying special attention to the bores and ports STIHL 020 T e Insert valve jet so that it is exactly square in the bore Press it home until it is flush with the bottom of the metering chamber Fit the inlet needle and the helical spring in their respective bores Insert
29. emove the muffler 4 1 e Set the piston to top dead center T D C This can be checked through the exhaust port e Fit flange 1 with sleeves 2 and screws 3 on cylinder exhaust port Do not tighten down yet Slide the sealing plate 4 between the flange and cylinder and tighten down the mounting screws Note The sealing plate must completely fill the space between the two mounting screws If the flange has only three holes drill a fourth hole as shown in the drawing STIHL 020 T e Remove the carburetor see 10 2 1 e Check that washer 1 and sleeve 2 are in position 1 2 eae Ap g Eo A iik po ai gt e Remove screw 1 from the test flange 2 e Fit the test flange on the carburetor studs e Fit nuts 1 and tighten down firmly 4 2 2 Pressure Test e Connect tester s pressure hose to nipple on test flange e Make sure the spark plug is properly tightened down e Close the vent screw 1 on the rubber bulb Use rubber bulb to pump air into the crankcase until the gauge indicates a pressure of 0 5 bar 7 25 psi If this pressure remains constant for at least 20 seconds the crankcase is airtight 17 4 2 3 Vacuum Test Oil seals tend to fail when sub jected to a vacuum i e the sealing lip lifts away from the crankshaft during the piston s induction stroke because there is no internal counterpressure An additional test can be carr
30. f the crank case for cracks and replace if necessary e To replace the ignition side of the crankcase pull off the impulse hose 1 Push out the grommets 2 and remove the short circuit wire 3 To replace the clutch side of the crankcase remove the ignition lead 1 bumper strips 2 spiked bumper 3 stud 4 and oil suction hose 5 with pickup body e Use a5 mm 0 2 drift to push out the vent valve STIHL 020 T e Unscrew the annular buffer 1 and disconnect cord 2 of filler cap 3 4 6 2 Installing the Crankshaft If the original crankcase is used again remove the gasket residue and clean the mating surfaces they must be cleaned very thoroughly to ensure a perfect seal Note If a new crankcase is installed stamp the machine number on the crankcase with 2 5 mm 0 1 figure stamps e Fit the annular buffer and tighten down to 6 Nm 4 4 Ibf ft e Fit end of filler cap retainer cord 1 in groove 2 and pull forwards to secure in position 26 e Pass short circuit wire 1 through hole and fit the grommets 2 and 3 e Push the impulse hose onto the nipple Coat thread of stud with Loctite see 11 2 e Use MB stud puller to screw in stud as far as stop STIHL 020 T vis w A P mT e Use a7 mm 0 3 drift to careful ly push home the valve small diameter facing up until it is re cessed about 1 mm
31. he chain sprocket cover see 3 1 e Remove the carburetor see 10 2 1 e Remove the washer 1 and sleeve 2 e Raise handle housing slightly and push manifold flange out of intake opening in handle housing at the same time Take out the lower front handle 1 mounting screw e Remove lower screw 2 from front annular buffer Note that groud wire 3 is secured with this screw e Pull the impulse hose off the nipple Remove center screw from front annular buffer STIHL 020 T Disconnect short circuit wire from the contact spring Install in the reverse sequence e Fit the manifold in the handle housing intake opening as follows Wind a piece of string approx 15 cm 6 long around the back of the manifold flange and pass the ends of the string through the intake opening e Push the handle housing against the manifold and pull the ends of the string outward at the same time Note The manifold flange is thus pulled through the handle housing intake opening without damaging the manifold 43 9 CHAIN LUBRICATION 9 1 Suction Hose Pickup Body Impurities gradually clog the fine pores of the filter with tiny particles of dirt This prevents the oil pump from supplying sufficient oil to the bar and chain In the event of problems with the oil supply system first check the oil tank and the pickup body Clean the oil tank if necessary Troubles
32. he inner spring loop slides into the lug on the rotor Note Check that the spring loop has engaged by turning the rope rotor slightly and letting it go it must spin back e Fit the washer 1 and install the spring clip 2 in the starter post groove Note Make sure the spring clip engages the pawl guide peg and points it in the clockwise direction The spring clip must be treated very carefully If it is bent or twisted during disassembly or assembly the rewind starter might malfunction e Tension the rewind spring see 6 5 35 6 3 Replacing the Starter Rope e Remove the rope rotor see 6 2 e Remove the remaining rope from the rope rotor Thread end of new rope through hole in side of rotor e Push rope into inner bore from the underside of the rotor Pull it through to the top and secure it with a simple overhand knot e Pull the rope back into the rotor so that the knot locates in the re cess STIHL 020 T Thread the other end of the rope through the guide bush from inside the fan housing Thread rope through the bottom of the starter grip and pull it out to the side 6 4 Replacing the Rewind Spring e Remove the rope rotor see 6 2 Take out the spring housing Use pliers to remove any remaining pieces of spring from the fan housing Note The new rewind spring is supplied ready for installation with a retainer 1 It should be lubri cated with a few
33. heel so that the mounting screws between the arms of the ignition magnet poles 1 are opposite module and the flywheel the ignition module 2 magnets e Unscrew the flywheel mounting e Press the ignition module nut 3 from the crankshaft against the flywheel and tighten down the mounting screws to a torque of 6 5 Nm 4 8 Ibf ft Important Tighten the screw next to flywheel first e Pull out the setting gauge and use a feeler gauge to check the air gap It should be 0 2 mm 0 008 p Fit the fan housing e Pull the ignition module forwards e Pull the flywheel off the crank shaft e Unscrew the ignition lead from the contact pin and pull it out of the high voltage output STIHL 020 T 33 Note If the flywheel is stuck screw puller 1 onto the crankshaft and tap the end of the puller to release flywheel Remove the puller raath me Inspect the condition of the flywheel 1 and magnet poles 2 If you find any cracks or other damage fit a new flywheel Installing the flywheel e Check that the Woodruff key is correctly positioned Important Clean the stub of the crankshaft and the flywheel hub bore with a standard commercial solvent based degreasant contain ing no chlorinated or halogenated hydrocarbons see 11 2 e Place the flywheel in position e Fit the mounting nut and tighten it down to 25 Nm 18 5 Ibf ft Assembly of the remaining parts is now a reve
34. hooting chart see 2 5 e Remove the chain sprocket see 3 3 e Take out the screws 1 e Remove the cover 2 Pull the worm off the crankshaft stub STIHL 020 T e Push suction hose off the nipple on the oil pump Pry the hose flange out of the crankcase e Remove the suction hose with pickup body e Pull the pickup body out of the suction hose e Wash the pickup body in white spirit and if possible blow out with compressed air Note If pickup body is damaged fit a new one e Remove oil tank filler cap Flush out the oil tank e Insert suction hose pickup body first in the crankcase Note Coat flange on hose with a little oil to simplify fitting Assembly is a reversal of the disassembly sequence 44 9 2 Vent Valve Flush out the oil tank Refit the cover e Fit the chain sprocket see 3 3 Fit the oil tank filler cap Replacing vent valve e Unscrew the oil tank filler cap A valve is installed in the tank wall to keep internal tank pressure equal to atmospheric pressure e Remove the chain sprocket see 3 3 Cleaning the valve Take out the screws e Unscrew the oil tank filler cap e Remove the cover e Drain the oil tank e Remove the chain sprocket see 3 3 e Pull out the upper bumper strip e Take out the screws 1 ly drive the vent valve out of the e Remove the
35. iderably easier if the machine is mounted on the assembly stand 1 This enables the machine to be swivelled to the best position for the ongoing repair and leaves both hands free The machine is secured to the stand by means of the guide bar mounting nut after removing the sprocket cover STIHL 1999 Andreas Stihl AG amp Co Waiblingen CONTENTS _ OX Ss eee ot Sk es N gt onnar wN N 2 1 2 2 2 3 2 4 2 5 2 6 3 1 3 2 3 3 3 4 3 5 3 6 4 1 4 2 4 2 1 4 2 2 4 2 3 4 3 4 4 4 4 1 4 4 2 4 5 4 6 4 6 1 4 6 2 Specifications Engine Fuel System Ignition System Cutting Attachment Special Accessories For User For Service Tightening Torques Troubleshooting Charts Clutch Chain Drive Chain Brake and Chain Tensioner Engine Ignition System Rewind Starter Chain Lubrication Fuel System Clutch Chain Drive Chain Brake and Chain Tensioner Disassembling Clutch Assembling Clutch Chain Sprocket Disassembling Chain Brake Assembling Chain Brake Chain Tensioner Engine Exhaust Muffler Leakage Test Preparations Pressure Test Vacuum Test Oil Seals Cylinder and Piston Removal Installation Piston Rings Crankcase Removing the Crankshaft Installing the Crankshaft STIHL 020 T w ahARHR RWW oO O ON OD 12 12 12 13 13 14 15 16 16 16 17 17 18 19 20 20 21 23 23 23 26 5 1 5 2 5 3 5 4 5 4 1 5 4 2 5 5 5 6
36. ied out with the vacuum pump to detect this kind of fault The preparations for this test are the same as for the pressure test see 4 2 1 e However if the indicated pressure drops the leak must be located and the faulty part replaced Note To find the leak coat the suspect area with oil and pressurize the crankcase again Bubbles will appear if a leak exists e Carry out the vacuum test see 4 2 3 e After finishing the test open the vent screw and disconnect the hose e Remove the test flange and refit the carburetor see 10 2 e Remove the flange and sealing plate e Connect the vacuum pump s suction hose to test flange nipple Install the muffler see 4 1 e Make sure spark plug is tight 142RA001 VA e Pull out the pump piston several times until the gauge indicates a vacuum of 0 5 bar 7 25 psi STIHL 020 T Note When you release the pump piston the non return valve auto matically seals the suction hose If the vacuum reading remains constant or rises to no more than 0 4 bar 5 8 psi within 20 seconds it can be assumed that the oil seals are in good condition However if the pressure continues to rise reduced vacuum in the crankcase the oil seals must be replaced even if no leaks were detected in the pressure test e Remove the test flange and refit the carburetor see 10 2 e Remove the flange and sealing plate e Install the muffler see 4 1 18
37. il able do not turn the high speed adjusting screw beyond the standard setting to make the mixture leaner A minor correction may be neces sary if the saw is used at high alti tudes mountains or near sea le vel For corrections to high speed adjusting screw H Use a tachometer do not exceed max permissible engine speed Engine can be damaged by lack of lubricant and overheating Maximum engine speed with bar and properly tensioned chain 14 500 r p m STIHL 020 T Check chain tension Check air filter and clean if necessary e Adjust idle speed correctly chain must not rotate e Start the saw warm up the engine Turn high speed adjusting screw H and low speed adjusting screw L clockwise for leaner mixture at high altitudes or counterclockwise for richer mixture at sea level Turn screws very slowly and care fully even slight adjustments produce a noticeable change in engine running behavior Corrections to high speed adjusting screw The setting of the high speed adjusting screw H affects the maximum off load engine speed If the setting is too lean the maximum permissible engine speed will be exceeded and increase the risk of engine damage MO 3 Adjusting engine idle speed A correction at the low speed adjusting screw L usually necessitates a change in the setting of the idle speed stop screw LA 3 Engine stops while idling Check standar
38. ine to the rewind spring Then carefully pull out the starter rope several times and allow it to rewind until its normal smooth action is restored If clogged with dirt or pitch the entire starter mechanism including the rewind spring must be removed and disassembled Take special care when removing the spring Wash all parts in paraffin or white spirit Lubricate the rewind spring and starter post with STIHL special lubricant see 11 2 before installing STIHL 020 T 6 2 Rope Rotor Troubleshooting chart see 2 4 e Take out the fan housing mount ing screws and remove the fan housing Relieving tension of rewind spring e Pull out the starter rope about 5 cm 2 and hold the rope rotor steady e While still holding the rope rotor steady take three full turns off the rope rotor e Pull out the rope with the starter grip and then let go of the rope rotor Note The rope rotor will spin back and relieve the tension of the rewind spring The rewind spring will not be under tension if the starter rope is broken e Remove the rope from the rotor e Use a screwdriver or suitable pliers to carefully remove the spring clip from the starter post e Take the washer and rope rotor with pawl off the starter post e Replace the worn or broken starter rope see 6 3 e Coat the bore in the rope rotor with STIHL special lubricant see 11 2 Fit the rotor on the starter post so that t
39. irty Remedy Replace oil seals Seal or replace manifold Replace gasket Replace crankcase Mount manifold correctly or replace Fit new piston rings Clean muffler inlet and exhaust replace spark arresting screen if fitted Thoroughly clean all cooling air openings and cylinder fins 2 3 Ignition System Warning Exercise extreme caution while carrying out maintenance and repair work on the ignition system The high voltages which occur can cause serious or fatal accidents Spark plug terminal firmly seated on spark plug yes no Remove spark plug Press terminal firmly onto spark Is it in good condition plug and fit spring if necessary Clean spark plug and reset electrode gap Faulty insulation on ignition Does spark test produce powerful spark lead or short circuit wire no yes Replace faulty ignition lead of short circuit wire Repair contact spring Insert screwdriver in place of spark plug in spark plug terminal and hold about 4 mm 1 8 away from ground Sparkover yes no Is air gap correct Fit new spark plug Adjust air gap 0 25 mm 0 010 in Does flywheel appear to Is spark test positive be in good condition yes Use ohmmeter to check ignition lead for break If break is detected replace ignition lead Does spark test now Fit new flywheel produce sparkover Is spark test positive no Replace ignition module Does engine Ignition system in order now run after positive spark te
40. ite grease Molykote grease STIHL 020 T Oil seals oil pump drive chain sprocket bearing chain tensioner switch shaft contact spring Packing high voltage output on ignition module Screws for throttle shutter and choke shutter sealing plug in carb Bar mounting stud Cleaning crankshaft stub Bearing bore in rope rotor rewind spring in rope rotor Guide peg on starter pawl Sliding and pivot points of chain brake 58
41. ith bottom of metering chamber Back off low speed adjusting screw slightly see Carburetor Adjustment Back off high speed adjusting screw slightly see Carburetor Adjustment Set inlet control lever flush with bottom of metering chamber Remove inlet needle clean and refit Clean bore 10 Condition Cause Remedy Diaphragm gasket leaking Metering diaphragm damaged or shrunk Fit new diaphragm gasket Fit new metering diaphragm Engine will not idle idle speed too high Throttle shutter opened too wide Reset idle speed adjusting screw by idle speed adjusting screw correctly Engine stalls at idle speed Idle jet bores or ports blocked Idle jet too rich Setting of idle speed adjusting screw incorrect throttle shutter completely closed Small plastic plate in valve jet does not close Clean jet bores and ports with compressed air Screw down low speed adjusting screw slightly see Carburetor Adjustment Set idle speed adjusting screw correctly Clean or renew valve jet Engine speed drops quickly under load low power Air filter dirty Tank vent faulty Leak in fuel line between tank and fuel pump Pump diaphragm damaged or fatigued Main jet bores or ports blocked Fuel pickup body dirty Fuel strainers dirty Clean air filter Clean or replace tank vent if necessary Seal or renew connections and fuel line Fit new pump diaphragm Clean bores an
42. ke e Fit lever with pivot pin and press it home as far as stop e Slide bell crank into end of hand guard The long arm 1 of the bell crank must point to the hole 2 Fit flat spring 1 in position e Locate the hand guard and bell crank on the pivot pins e Now press the flat spring 1 down and push the hand guard and bell crank fully home e Fit hand guard in the sprocket cover crank Attach brake band to the bell 14 3 6 Chain Tensioner e Press the brake band into the e Remove chain sprocket cover e Pull the spur gear 1 out of the sprocket cover see 3 1 cover 2 Important Coat sliding and bear e Remove screw from cover ing points of chain brake with Moly kote grease see 11 2 Do not lubricate the brake band e Hook the brake spring onto the e Take out the complete chain e Pull off the tensioner slide 1 bell crank tensioner e Remove the adjusting screw 2 e Inspect the teeth on the spur gear and adjusting screw If the teeth are damaged replace both parts Reverse the above sequence to install the chain tensioner Note Coat teeth of adjusting screw and spur gear with grease see 11 2 before refitting e Use the assembly tool 2 to attach e Remove the thrust pad 1 the brake spring 1 to the anchor pin e Rotate the spur gear 2 to unscrew the adjusting screw 3 fully from the Fit the segmen
43. ked Teeth on pump piston and or worm worn Remedy Fill up with oil Clean oil inlet hole Wash intake hose and pickup body strainer in white spirit and blow out with compressed air replace if necessary Clean or replace valve Fit new pump piston and or new worm Condition Machine losing chain oil Oil pump delivers too little oil 2 6 Fuel System Condition Carburetor floods engine stalls Poor acceleration STIHL 020 T Cause Bore in pump housing worn Control screw and or control edge on pump piston worn Bore in pump housing Remedy Fit new pump housing Fit new control screw and or pump piston Fit new pump housing worn Cause Inlet needle not sealing Foreign matter in valve seat or cone damaged Inlet control lever sticking on spindle Helical spring not located on nipple of inlet control lever Perforated disc on diaphragm is deformed and presses constantly against inlet control lever Inlet control lever too high relative to design position Idle jet too lean Main jet too lean Inlet control lever too low relative to design position Inlet needle sticking to valve seat Connecting bore to atmosphere blocked Remedy Remove and clean or replace inlet needle clean fuel tank pickup body and fuel line if necessary Free off inlet control lever Remove inlet control lever and refit correctly Fit new metering diaphragm Set inlet control lever flush w
44. l seal over the installing sleeve closed side of seal facing crankcase and use press sleeve 1 to press it home e Remove the installing sleeve Fit the flywheel see 5 5 19 4 4 Cylinder and Piston 4 4 1 Removal Always check and if necessary repair the fuel system carburetor air filter and ignition system before looking for faults on the engine e Remove the tank housing see 10 6 e Remove the spark plug e Release and unscrew the four cylinder base screws through the holes in the cylinder fins e Pull the cylinder off the piston e Remove the cylinder gasket STIHL 020 T her 2 e Pull the manifold 1 off the intake port e Inspect the cylinder and replace it if necessary Note If a new cylinder has to be installed always fit the matching piston Replacement cylinders are only supplied complete with piston for this reason Important Before removing the piston decide whether or not the crankshaft has to be removed as well To remove the flywheel block the crankshaft by sliding the wooden assembly block between the piston and crankcase e Use a scriber or similar tool to ease the hookless snap rings out of the grooves in the piston bosses e Now use the assembly drift 2 to push the piston pin 1 out of the piston Note If the piston pin is stuck tap the end of the drift lightly with a hammer if necessary Important Hold the piston steady
45. linder bore Displacement Bore Stroke Compression ratio Power output Max torque Max permissible engine speed with bar and chain Mean idle speed Bearings Piston pin diameter Connecting rod length Rewind starter Reserve pull on rope rotor Starter rope Clutch Diameter Clutch engages at Crankcase leakage test at gauge pressure under vacuum Carburetor Standard setting High speed adjusting screw H Low speed adjusting screw L Carburetor leakage test at gauge pressure Fuel tank capacity Octane number Fuel mixture Mix ratio Air filter 35 2 cm 2 15 cu in 40 mm 1 57 in 28 mm 1 10 in 7 41 1 6 kW 2 2 bhp 1 8 Nm 1 3 Ib ft at 7 500 r p m 14 000 r p m 2 800 r p m Crankshaft supported in heavy duty roller bearings needle cages on small and big ends 9 mm 0 35 in 49 mm 1 93 in Pawl system min 1 2 turn 3 0 mm 0 12 in dia 800 mm 31 5 in long Centrifugal clutch without linings 66 mm 2 60 in 3 900 r p m 0 5 bar 7 25 psi 0 5 bar 7 25 psi Diaphragm carburetor Back off approx 1 turn Back off approx 1 turn 0 4 bar 5 8 psi 0 37 0 8 US pt mind 90 RON USA CAN pump octane min 87 unleaded Regular brand name gasoline and two stroke engine oil 50 1 with Stihl two stroke engine oil 25 1 with other brand name two stroke air cooled engine oils Dual ply synthetic fabric or flocked wire mesh element and fo
46. lves of the e Lift away annular buffer 2 crankcase STIHL 020 T 24 e Fit threaded sleeve 1 on the spindle of service tool AS 2 and screw it on counterclockwise as far as stop left hand thread e Hold the crankshaft steady and rotate spindle to screw threaded sleeve onto crankshaft stub as far as it will go e Now release the crankshaft and hold service tool steady and continue turning spindle until service tool locates against the crankcase Fit collar nut for sprocket cover on stud and screw on fingertight STIHL 020 T e Turn spindle of service tool clockwise until the crankshaft is pressed out of the roller bearing The two halves of the crankcase separate during this process e Pull the ignition lead 1 out of the grommet 2 Pull the crankshaft out of the roller bearing e The crankshaft 1 connecting rod 2 and needle bearing form an inseparable unit This means that the crankshaft must always be replaced as a complete unit in the event of damage to any one of these parts e When fitting a replacement crankshaft always install new oil seals and roller bearings e Remove the gasket from the crankcase mating face e Carefully drive the oil seals out of the two halves of the crankcase 25 e Carefully knock the roller bear ings out of the two halves of the crankcase e Inspect both halves o
47. n a diagonal pattern e Fit the fuel tank see 10 6 22 4 5 Piston Rings 4 6 Crankcase 4 6 1 Removing the Crankshaft e Remove the piston see 4 4 1 e Remove the cylinder see 4 4 1 e Disconnect the short circuit wire 1 from the ignition module 2 e Remove rings from piston e Drain the oil tank e Take out the screws 3 e Use a piece of old piston ring to e Unscrew the mounting nut 1 scrape the grooves clean e Pull the flywheel 2 off the crankshaft Install the new piston rings in the Note If the flywheel is stuck screw e Pull the ignition module forwards grooves so that the radii face puller 1 onto the crankshaft and upward tap the end of the puller to release e Unscrew ignition lead from flywheel Remove the puller contact pin and pull it out of the e Install the piston see 4 4 2 ignition module e Take Woodruff key out of slot in e Unscrew clutch from crankshaft stub of crankshaft Caution Clutch has left hand thread STIHL 020 T 23 e Pull the chain sprocket off the e Pull the suction hose 1 off the oil e Pull out the plug crankshaft pump 2 e Take out the screws 3 and remove the oil pump e Take out the screws 1 e Remove the piston see 4 4 1 e Take out the screws 1 and 3 e Remove the cover 2 e Withdraw the chain tensioner 2 e Pull off the worm e Take out the screw 1 e Unscrew the six mounting screws which join the two ha
48. n timing on the electronic breakerless magneto ignition system is fixed at 2 4 mm 0 094 B T D C at 8 000 r p m and is not adjustable However in view of the permiss ible tolerances in the electronic circuit it may vary between 2 0 and 2 8 mm 0 08 and 0 11 B T D C at 8 000 r p m Since there is no mechanical wear in these systems ignition timing cannot get out of adjustment However an internal fault in the circuit can alter the switching point in such a way that a spark test will still show the system to be in order although timing is outside the permissible tolerance This will impair engine starting and running behavior 32 5 4 2 Removing and Installing 5 5 Flywheel If necessary remove the wire Removing the flywheel retainer from the module e Use the locking strip to block the Note Before fitting the ignition piston see 3 1 lead pack the high voltage output with STIHL multipurpose grease e Remove the fan housing see 11 2 see 6 2 Important Do not use graphite grease Molykote or silicone insulating paste for this job e Remove the fan housing e Coat the threads of the mounting see 6 2 screws with Loctite see 11 2 Place the module in position insert e Pull the short circuit wire 1 off the screws with washers but do not the ignition module and out of tighten them down yet the retainer 2 e Remove the ignition module e Slide the setting gauge 1 e Rotate the flyw
49. ottle shaft 2 STIHL 020 T 51 e After fitting the throttle shaft Removing the choke shaft e Pull out the choke shaft check that the torsion spring is correctly positioned e Disconnect the torsion spring Remove the torsion spring 1 1 from the groove in the throttle shaft 2 Fit the throttle shutter so that the e Unscrew the choke shutter e Position the choke shutter so that hole 1 is at the same side as the fastening screw the outer hole 1 points towards torsion spring 1 and the larger the metering end cover 2 and the notch 3 points towards the fuel e Remove the choke shutter inner hole 3 towards the torsion pump end cover 4 spring 4 e Coat thread of fastening screw e Coat the fastening screw with with Loctite see 11 2 and tighten Loctite see 11 2 and tighten it down firmly down firmly e Carry out the leakage test see 10 2 2 Install the carburetor see 10 2 1 e Remove the E clip STIHL 020 T 52 10 3 Carburetor Adjustment E N po LLL Standard setting If the carburetor has to be adjusted from scratch first carry out the standard setting e Carefully screw in both adjusting screws clockwise until they are hard against their seats Now make the following adjust ments H High speed adjusting screw 1 backed off 1 full turn L Low speed adjusting screw 2 backed off 1 full turn Note If no tachometer is ava
50. ounterclockwise Fit new springs Loud noises Clutch springs stretched or fatigued Needle cage damaged Clutch shoe retainer broken Clutch shoes and carrier worn Replace all clutch springs Fit new needle cage Fit new retainer Fit new clutch Chain sprocket wears rapidly Chain not properly tensioned Tension chain as specified Chain wears rapidly Chain not properly tensioned Poor chain lubrication Worn chain sprocket Tension chain as specified Check chain lubrication and rectify problem Fit new sprocket Chain does not stop immediately when brake is activated Brake spring broken Brake band stretched or broken Fit new brake spring Fit new brake band STIHL 020 T 2 2 Engine Always check and if necessary repair the following parts before looking for faults on the engine Air filter Fuel system Carburetor Ignition system Condition Engine does not start easily stalls at idle speed but operates normally at full throttle Engine does not deliver full power or runs erratically Engine overheating STIHL 020 T Cause Oil seals in crankcase damaged Manifold leaking Cylinder base gasket leaking Crankcase damaged cracks Secondary air seepage through poorly mounted or faulty manifold Piston rings leaking or broken Muffler carbonized Insufficient cylinder cooling Air inlets in fan housing blocked or cooling fins on cylinder very d
51. rsal of the disassembly sequence STIHL 020 T 5 6 Ground Wire Short Circuit Wire Ground wire e Remove the chain sprocket cover e Remove the handle molding see 8 2 e Remove screw 1 which secures ground wire 2 to annular buffer e Pull ground wire off the contact spring 3 Assemble in the reverse sequence Short circuit wire e Remove the ignition lead see 5 3 e Remove the handle molding see 8 2 e Take out handle housing mount ing screw 1 and screws 2 from annular buffer 3 e Remove the annular buffer e Pull the short circuit wire 1 off the contact spring e Pull out the grommet 2 and slip it off the short circuit wire Pull the short circuit wire out of the crankcase and grommet 1 Install short circuit wire in the reverse sequence we Note Thread short circuit wire through the side of the crankcase and pull it up to the top 34 6 REWIND STARTER 6 1 Routine Maintenance If the action of the starter rope becomes very stiff and the rope rewinds very slowly or not com pletely it can be assumed that the starter mechanism is in order but plugged with dirt At very low outside temperatures the lubricating oil on the rewind spring may thicken and cause the spring windings to stick together This has a detrimental effect on the function of the starter mechanism In such a case it is sufficient to apply a few drops of paraffin keros
52. s Throttle Trigger as e Remove the choke throttle rod e Remove the throttle trigger e Remove the front upper annular see 8 2 see 8 3 buffer see 7 e Take out the interlock lever e Pull out the switch shaft e Pull out contact spring 1 for ground wire 2 e Disconnect the ground wire e Remove the throttle trigger e Push the contact spring 2 slightly e Pull the short circuit wire off the to one side and fit the switch shaft contact spring 1 e Install the throttle trigger see 8 3 Note Lubricate switch shaft with grease see 11 2 e Take the torsion spring off the e Pull out the contact spring throttle trigger Assemble in the reverse sequence Assemble in the reverse sequence STIHL 020 T 41 8 6 Double Lever 8 7 Front Handle Choke Throttle Remove the choke throttle rod e Pull out the double lever e Remove the switch shaft see 8 2 see 8 4 Assemble in the reverse sequence Choke double lever Take out the upper front handle mounting screw e Pull out the double lever Note Note that short choke rod e Take out lower front handle must be fitted in the upper hole mounting screw Throttle double lever Pull front handle out of handle housing Remove the carburetor see 10 2 1 Disconnect short throttle rod STIHL 020 T 42 8 8 Handle Housing Remove center screw from rear annular buffer e Remove t
53. s itself onto the rotor STIL sete Note The rewind spring is correctly tensioned when the starter grip sits firmly in the rope guide bush without drooping to one side If this is not the case tension the spring by one additional turn When the starter rope is fully extended it must still be possible to rotate the rope rotor at least another half turn before maximum spring tension is reached If this is not the case pull the rope out hold the rope rotor steady and take off one turn of the rope Do not overtension the rewind spring as this will cause it to break e Refit the fan housing 37 6 6 Pawl 6 7 e Remove the fan housing e Remove the spring clip from the starter post see 6 2 Note Do not pull the rope rotor off the starter post The wear on the guide bush is accelerated by the starter rope being pulled sideways The wall of the guide bush eventually wears through becomes loose and has to be replaced e Remove the rope rotor see 6 2 Starter Rope Guide Bush e Insert the screw spindle 1 of the installing tool through the bush from inside the housing e Pull the pawl out of the rope rotor e Pull starter rope out of recess 1 in rope rotor e Coat peg of new pawl with graphite grease see 11 2 and fit it in position Undo the knot 2 e Pull starter rope out of rope rotor and guide bush e Use a suitable tool to pry the old bush out of the fan housing
54. spindle in the inlet control lever engage clevis in annular groove on the head of the inlet needle and tighten down the round head screw Make sure that the helical spring locates on the control lever s nipple e Check easy action of the inlet control lever Important The top of the inlet control lever must be level with the bottom of the metering chamber If necessary use suitable pliers to carefully bend the lever After fitting new sealing plug fill gap between carburetor body and plug with Loctite see 11 2 e Carefully screw the high speed 1 and low speed 2 adjusting screws down onto their seats and then back them off one full turn e Fit metering diaphragm on end cover e Place gasket on metering diaphragm 50 Cy e Position end cover on carburetor e Fit the end cover e Remove the E clip body so that peg 1 engages the bore 2 e Insert screws and tighten down firmly e Insert screws and tighten down firmly Note The pump diaphragm and gasket are held in position by inte grally cast pegs on the end cover Insert the fuel strainer at the Removing the throttle shaft e Pull out the throttle shaft pump side Unscrew the throttle shutter e Fit the pump diaphragm fastening screw Take out the throttle shutter e Place gasket on pump e Disconnect the torsion spring e Remove the torsion spring diaphragm 1 from the groove in the thr
55. st Look for fault in fuel system and no carburetor STIHL 020 T 8 2 4 Rewind Starter Condition Starter rope broken Rewind spring broken Starter rope can be pulled out almost without resistance crankshaft does not turn Starter rope is difficult to pull and rewinds very slowly 2 5 Chain Lubrication Cause Rope pulled out too vigorously as far as stop or over edge i e not vertically Normal wear Spring overtensioned no reserve when rope is fully extended Very dirty or corroded Guide peg on pawl or pawl itself is worn Spring clip fatigued Starter mechanism is very dirty dusty conditions Lubricating oil on rewind spring becomes viscous at very low outside tem peratures spring windings stick together Remedy Fit new starter rope Fit new starter rope Fit new rewind spring Fit new rewind spring Fit new pawl Fit new spring clip Thoroughly clean complete starter mechanism Apply a few drops of kerosine paraffin to spring then pull rope carefully several times until normal action is restored Important In the event of trouble with chain lubrication system always investigate the other possible sources of faults before disassembling the oil pump Condition Chain receives no oil STIHL 020 T Cause Oil tank empty Oil inlet hole in guide bar is blocked Intake hose or pickup body strainer clogged or intake hose ruptured Valve in oil tank bloc
56. t and tighten tensioner slide 4 screws to 3 2 Nm 2 4 Ibf ft STIHL 020 T 15 4 ENGINE 4 2 Leakage Test 4 1 Exhaust Muffler Defective oil seals and gaskets or cracks in castings are the usual causes of leaks Such faults allow supplementary air to enter the engine and thus upset the fuel air mixture This makes adjustment of the prescribed idle speed difficult if not impossible Moreover the transition from idle Troubleshooting chart see 2 2 e Take out the screws speed to part or full throttle is not smooth e Remove sprocket cover Lift lower casing away from see 3 1 upper casing The crankcase can be checked thoroughly for leaks with the Take out the screw 1 carburetor and crankcase tester and the vacuum pump e Remove the cover 2 6 Q y Lk nena i LAY SSS a SS 4 L J e Remove mounting screws from e Take out the screw underside of machine e Remove baffle from guide in upper casing e Clean baffle or fit a new one Note If baffle is equipped with spark arresting screen make sure the spark arresting screen is refitted Reassemble in the reverse sequence Note Install a new gasket Tighten screws of upper casing to 4 Nm 3 Ibf ft and muffler mounting screws to 11 5 Nm 8 5 Ibf ft Pull out the muffler e Remove the gasket STIHL 020 T 4 2 1 Preparations R

STIHL 020 T

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