STIHL BG 56, 66, 86, SH 56, STIH)

Transcription

1 STIHL BG 56, 66, 86, SH 56, STIH)

2 Contents RA_96_0_0_0. Introduction. Safety Precautions 3 3. Specifications 4 3. Engine 4 3. Fuel System Ignition System Tightening Torques 5 4. Troubleshooting 7 4. Rewind Starter 7 4. Blower Ignition System Carburetor 4.5 Engine 4 5. Engine 5 5. Muffler / Spark Arresting Screen 5 5. Leakage Test Preparations Vacuum Test Pressure Test Oil Seals Engine Removing and Installing Cylinder Removing and Installing Crankshaft Removing and Installing Bearings / Crankshaft Piston Piston Rings Piston Rings 9 6. Ignition System Ignition Module Removing and Installing Ignition Timing Testing the Ignition Module Spark Plug Boot Flywheel Short Circuit Wire Testing Removing and Installing Ground Wire Stop Switch Ignition System Troubleshooting 40 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH Rewind Starter General Removing and Installing Pawl ErgoStart Rope Rotor Starter Rope / Grip Tensioning the Rewind Spring Replacing the Rewind Spring Rope Guide Bushing 5 8. Antivibration System Removing and Installing Handle on SH 86, SH 86 C, BG 66 C, BG 86, BG 86 C Control Levers Switch Positions Setting Lever on SH 86, SH 86 C, BG 66 C, BG 86, BG 86 C Throttle Trigger on Models SH 56, SH 56 C, BG 56, BG 56 C, BG Throttle Trigger on Models SH 86, SH 86 C, BG 66 C, BG 86, BG 86 C Fuel System Air Filter Baffle / Filter Housing Removing and Installing the Carburetor Leakage test Servicing the Carburetor Metering Diaphragm / Manual Fuel Pump Inlet Needle Pump Diaphragm Throttle Lever / Rotary Knob Adjusting Screws Adjusting the Carburetor Basic Setting Standard Setting Adjusting Engine Idle Speed Throttle Rod Spacer Flange Removing and Installing Tank Vent Testing Removing and Installing Fuel intake Pickup Body Fuel Hoses Fuel Tank Cap 76. Blower and Vacuum Attachment 77. Intake Screen 77. Blower Wheel 78.3 Removing and Installing Blower Housing on Models SH 56, SH 56 C, BG 56, BG 56 C, BG Removing and Installing Blower Housing on Models SH 86, SH 86 C, BG 66 C, BG 86, BG 86 C Removing and Installing Handle Housing on Models SH 86, SH 86 C, BG 66 C, BG 86, BG 86 C 80.4 Blower Tube BG Models 80.5 Elbow SH Models 8.6 Suction Tube SH Models 8. Special Servicing Tools 8 3. Servicing Aids 84 q ANDREAS STIHL AG & Co. KG, 0

3 . Introduction This service manual contains detailed descriptions of all the repair and servicing procedures specific to this power tool. You should make use of the illustrated parts lists while carrying out repair work. They show the installed positions of the individual components and assemblies. Refer to the latest edition of the relevant parts list to check the part numbers of any replacement parts. A fault on the machine may have several causes. To help locate the fault, consult the chapter on "Troubleshooting" and the "STIHL Service Training System" for all assemblies. 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 revised edition is issued. The special tools mentioned in the descriptions are listed in the chapter on "Special Servicing Tools" in 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. Symbols are included in the text and pictures for greater clarity. The meanings are as follows: In the descriptions: : = Action to be taken that is shown in the illustration (above the text) = Action to be taken that is not shown in the illustration (above the text) In the illustrations: A Pointer adirection of movement b 4. = Reference to another chapter, i.e. chapter 4. in this example. Service manuals and all technical information bulletins are intended exclusively for the use of properly equipped repair shops. They must not be passed to third parties. Always use original STIHL replacement parts. They can be identified by the STIHL part number, the STIH) logo and the STIHL parts symbol ( This symbol may appear alone on small parts. Storing and disposing of oils and fuels Collect fuel or lubricating oil in a clean container and dispose of it properly in accordance with local environmental regulations. BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

4 . Safety Precautions If the power tool is started up in the course of repairs or maintenance work, observe all local and countryspecific safety regulations as well as the safety precautions and warnings in the instruction manual. Gasoline is an extremely flammable fuel and can be explosive in certain conditions. Always wear suitable protective gloves for operations in which components are heated for assembly or disassembly. Improper handling may result in burns or other serious injuries. Do not smoke or bring any fire, flame or other source of heat near the fuel. All work with fuel must be performed outdoors only. Spilled fuel must be wiped away immediately. Always perform leakage test after working on the fuel system and the engine. BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 3

5 3. Specifications 3. Engine BG 56, SH 56 BG 66, BG 66 C BG 86, SH 86 Displacement: 7. cm 3 7. cm 3 7. cm 3 Bore: 34 mm 34 mm 34 mm Stroke: 30 mm 30 mm 30 mm Engine power to ISO 793: 0.70 kw (.0 bhp) 0.60 kw (0.8 bhp) 0.8 kw (. bhp) Maximum permissible engine speed (with nozzle): 6,800 rpm 5,800 rpm 7,00 rpm Idle speed:,500 rpm,500 rpm,500 rpm Engine leakage test under vacuum: 0.5 bar at gauge pressure: 0.5 bar 3. Fuel System Carburetor leakage test at gauge pressure: Operation of tank vent at gauge pressure: Fuel: 0.8 bar 0.5 bar as specified in instruction manual 3.3 Ignition System Air gap between ignition module and fanwheel: mm Spark plug (resistor type): Electrode gap: BOSCH USR4AC NGK CMR 6 H 0.5 mm 4 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

6 3.4 Tightening Torques DG and P (Plastoform) screws are used in polymer and light metal 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 impairing 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 Nut M 5 Filter housing/carburetor/spacer flange 3.5 Screw P 5x8 Blower housing, outer/inner 3.0 Screw D 5x4 Blower housing, inner/crankcase 9.0 Screw D 5x4 Blower housing, inner/engine pan 8.0 Screw D 5x4 Blower housing, inner/cylinder 8.0 Nut M 8x L Blower wheel/crankshaft.0 Screw P 5x8 Handle/cover/plug 3.0 Screw P 5x8 Handle/handle frame/plug 3.0 Screw P 5x8 Handle molding/blower housing, inner 3.0 Screw P 5x8 Handle molding/handle/handle frame/ 3.0 plug Screw D 5x60 Engine pan/crankcase/cylinder 9.0 Screw D 5x0 Fan housing/spiral housing 6.0 Screw D 5x0 Muffler/cylinder 9.0 Nut M 8x Flywheel/crankshaft 7.0 ) Screw D 5x0 Spiral housing/crankcase 6.0 Screw D 5x0 Spiral housing/engine pan 6.0 M 0x Spark plug.0 Screw D 4x8 Ignition module/cylinder 3.5 Screw D 5x0 Spacer flange/cylinder, stage.0 Spacer flange/cylinder, stage 6.0 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 5

7 Remarks: ) Degrease crankshaft/flywheel and mount oil-free Use the following procedure when refitting a DG or P 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 and weaken the assembly. Power screwdriver setting for polymer: DG and P screws max. 500 rpm Do not use an impact wrench for releasing or tightening screws. Do not mix up screws with and without binding heads. 6 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

8 4. Troubleshooting 4. Rewind Starter Condition Cause Remedy Starter rope broken Rope pulled out too vigorously as far as stop or over edge, i.e. not vertically Fit new starter rope Normal wear Fit new starter rope Starter rope does not rewind Very dirty or corroded Clean or replace rewind spring Insufficient spring tension Check rewind spring and increase tension Rewind spring worn Fit new rewind spring Starter rope cannot be pulled out far enough Spring overtensioned Check rewind spring and reduce tension Starter rope can be pulled out almost without resistance (crankshaft does not turn) Guide peg on pawl or pawl itself is worn Fit new pawl Pawl spring fatigued Fit new pawl spring Models with ErgoStart Spring broken or fatigued Fit new ErgoStart spring Starter rope is difficult to pull or rewinds very slowly Starter mechanism is very dirty Thoroughly clean complete starter mechanism Lubricating oil on rewind spring becomes viscous at very low outside temperatures (spring windings stick together) Coat rewind spring with a small amount of standard solvent-based degreasant (containing no chlorinated or halogenated hydrocarbons), then pull rope carefully several times until normal action is restored BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 7

9 4. Blower Always switch off the engine before working on the blower. Condition Cause Remedy No suction Blower wheel loose Tighten down nut on blower wheel firmly Blower wheel blocked Clean blower housing Poor suction Catcher bag full Empty the catcher bag Fan outlet blocked Blower wheel worn or too many blades broken Clean fan housing and outlet Fit a new blower wheel Poor blowing performance Intake screen very dirty Clean intake screen and fan housing Blower wheel loose Blower wheel worn or too many blades broken Tighten down nut on blower wheel firmly Fit a new blower wheel Leaves are not properly shredded Shredder blade loose or worn Tighten down or replace the shredder blade 8 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

10 4.3 Ignition System 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. Condition Cause Remedy Engine runs roughly, misfires, temporary loss of power Spark plug boot is loose Press boot firmly onto spark plug and fit new spring if necessary Spark plug sooted, smeared with oil Clean the spark plug or replace if necessary. Fuel/oil mixture too much oil Use correct mixture of fuel and oil Incorrect air gap between ignition module and flywheel Set air gap correctly Flywheel shows signs of damage (e.g. scores) or pole shoes have turned blue Install new flywheel Ignition timing out of adjustment, flywheel warped, key in flywheel sheared Install new flywheel Flywheel magnetization weak pole shoes have turned blue Install new flywheel Irregular spark Check operation of stop switch and ignition module Check ignition lead/module, replace ignition module if necessary Check ignition lead and short circuit wire for damaged insulation or break and replace if necessary. Check operation of spark plug. Clean the spark plug or replace if necessary. The carburetor or engine may also be the cause of poor engine running behavior BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 9

11 Condition Cause Remedy No spark Spark plug faulty Install new spark plug Faulty insulation or short in short circuit wire Break in ignition lead or insulation damaged Ignition module faulty Check short circuit wire for short circuit to ground Check ignition lead, replace ignition module if necessary. Install new ignition module 0 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

12 4.4 Carburetor Condition Cause Remedy Carburetor floods; engine stalls Inlet needle not sealing Foreign matter between valve seat and sealing cone or sealing cone worn Remove and clean the inlet needle, clean the carburetor Inlet control lever sticking on spindle Clean the inlet control lever or replace if necessary. Helical spring not located on nipple of inlet control lever Remove the inlet control lever and refit it correctly Perforated disc on diaphragm is deformed and presses constantly against the inlet control lever Fit a new metering diaphragm Poor acceleration Setting of low speed screw too lean Check basic carburetor setting, correct if necessary Setting of high speed screw too lean Inlet needle sticking to valve seat Diaphragm gasket leaking Metering diaphragm damaged or shrunk Spacer flange damaged Check basic carburetor setting, correct if necessary Remove inlet needle, clean and refit Fit new diaphragm gasket Fit a new metering diaphragm Install new spacer flange BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

13 Condition Cause Remedy Engine will not idle, idle speed too high Throttle shutter opened too wide by idle speed screw (LA) Reset idle speed screw (LA) correctly Oil seals/engine leaking Seal or replace oil seals/engine Throttle shutter stiff or torsion spring on throttle shaft fatigued or broken Free off throttle shaft or install new carburetor Engine stops while idling Idle jet bores or ports blocked Clean the carburetor Low speed screw too rich or too lean Reset low speed screw (L) correctly Setting of idle speed screw incorrect throttle shutter completely closed Reset idle speed screw (LA) correctly BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

14 Condition Cause Remedy Engine speed drops quickly under load low power Air filter dirty Clean air filter or replace if necessary Throttle shutter not opened fully Check rod Tank vent faulty Replace tank vent Fuel pickup body dirty Install new pickup body Fuel strainer dirty Clean fuel strainer in carburetor, replace if necessary Leak in the fuel suction hose Fit new fuel suction hose Setting of high speed screw (H) too rich Check basic carburetor setting, correct if necessary Main jet bores or ports blocked Clean or replace the carburetor Pump diaphragm damaged or fatigued Fit new pump diaphragm BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 3

15 4.5 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 Cause Remedy Engine does not start easily, stalls at idle speed, but operates normally at full throttle Oil seals in crankcase damaged Replace the oil seals Engine leaking or damaged (cracks) Seal or replace the engine Engine does not deliver full power or runs erratically Piston rings worn Fit new piston rings Muffler / spark arresting screen carbonized Clean the muffler (inlet and exhaust), replace spark arresting screen, replace muffler if necessary Air filter dirty Replace air filter Fuel suction hose kinked or torn Fit new hoses or position them free from kinks Tank vent faulty Check the tank vent and replace if necessary. Engine overheating Insufficient cylinder cooling. Air inlets in fan housing blocked or cooling fins on cylinder very dirty Thoroughly clean all cooling air openings and the cylinder fins. 4 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

16 5. Engine 5. Muffler / Spark Arresting Screen Spark arresting screen (not all markets) Always check and, if necessary, repair the fuel system, carburetor, air filter and ignition system before looking for faults on the engine. Troubleshooting, b 4.5 Remove the fan housing, b 7. 96RA004 TG 96RA00 TG Insert the screws trough the holes in the muffler. 96RA000 TG : Unscrew the stub with spark arresting screen (). Clean the stub with screen () or replace if necessary. Reassemble in the reverse sequence. : Push the gasket () over the screws the gasket is held in position. : Take out the screws (arrows). Remove the muffler (), check and replace if necessary. 96RA005 TG : Inspect and clean the sealing faces (arrows), b 3 96RA003 TG Carefully place the muffler () in position. : Line up the screws (arrows) and check the position of the gasket. 96RA00 TG Insert the screws (arrows) and tighten them down firmly. Install the fan housing, b 7. : Remove the gasket (). Tightening torques, b 3.4 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 5

17 5. Leakage Test : Fit the spark plug () and tighten it down firmly. 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 upset the fuel-air mixture. This makes adjustment of the prescribed idle speed difficult, if not impossible. Moreover, the transition from idle speed to part or full throttle is not smooth. Tightening torques, b RA000 TG Check that the gasket () is in position. 96RA008 TG Always perform the vacuum test first and then the pressure test. : Loosen the screws (arrows). The engine can be checked thoroughly for leaks with the pump Lift the muffler () Preparations O 6 96RA009 TG Test flange () can be modified as shown above. 96RA007 TG Remove the fan housing, b 7. Pull the boot off the spark plug. : Unscrew the spark plug (). Set the piston to top dead center. This can be checked through the spark plug hole. 96RA006 TG : Fit the sealing plate () between the cylinder exhaust port and muffler and tighten down the screws moderately. The sealing plate must completely fill the space between the two screws. Remove the carburetor, b 0.3 : Fit the test flange () RA00 TG 6 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

18 5..3 Pressure Test : Fit the nuts (arrows) and tighten them down firmly. 5.. Vacuum Test Oil seals tend to fail when subjected 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. A test can be carried out with pump to detect this kind of fault. 96RA0 TG : Push ring () to the left : Operate the lever () until the pressure gauge (arrow) indicates a vacuum of 0.5 bar. If the vacuum reading remains constant, or rises to no more than 0.3 bar within 0 seconds, it can be assumed that the oil seals are in good condition. However, if the pressure continues to rise (reduced vacuum in the engine), the oil seals must be replaced, b 5.3. After finishing the test, push the ring to the right to vent the pump. Continue with pressure test, b RA03 TG Carry out the same preparations as for the vacuum test, b 5.. Always carry out the pressure test after the vacuum test, b RA0 TG : Connect pressure hose () of pump to the nipple (arrow). 96RA0 TG : Connect suction hose () of pump to the nipple (arrow). BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 7

19 : Push ring () to the right : Operate the lever () until the pressure gauge (arrow) indicates a pressure of 0.5 bar. If this pressure remains constant for at least 0 seconds, the engine is airtight. If the pressure drops, the leak must be located and the faulty part replaced. To find the leak, coat the suspect area with oil and pressurize the engine. Bubbles will appear if a leak exists. After finishing the test, push the ring to the left to vent the pump disconnect the hose. Remove the test flange. Install the carburetor, b 0.3 Loosen the muffler and pull out the sealing plate. Tighten down the muffler firmly. Reassemble all other parts in the reverse sequence. Tightening torques, b RA04 TG 5.3 Oil Seals The engine must be disassembled to replace the oil seals. Remove the engine, b 5.4 Remove the engine pan, b 5.6 Pull the crankshaft upwards a little but not out of the cylinder. : Pull off the oil seals (). Clean the sealing faces and install new oil seals, b 5.6 Install the engine pan, b 5.6 Degrease the crankshaft taper, b 3 Install the engine, b RA96 AM 5.4 Engine Removing and Installing The complete engine has to be removed for access to the piston, cylinder and crankshaft. Remove the fan housing, b 7. Pull the boot off the spark plug. Remove the air filter, b 0. Remove the filter housing, b 0. Remove the throttle rod, b 0.6 Unscrew the spark plug. : Disconnect the short circuit wire () and ground wire (). 96RA00 TG 96RA0 TG Put the wires to one side. 8 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

20 Installing : Disconnect the fuel suction hose () and fuel return hose () from the stubs (arrows) on the connector. Remove the blower wheel, b. : Take out the screws (arrows). 96RA0 TG 96RA03 TG Check the engine and install a new cylinder, piston, crankshaft or crankcase if necessary after removing the muffler, ignition module and spacer flange. It is not necessary to disassemble the engine any further to replace the oil seals. Inspect the oil seals and replace if necessary, b 5.6 : Check that the oil seals are correctly seated they must be flush with the edge (arrow) of the crankcase. 96RA05 TG Take care to avoid pinching the short circuit and ground wires between the engine and blower housing. : Push the straight crankshaft stub () into the blower housing bore (arrow). Push the engine against the blower housing. 96RA06 TG 96RA07 TG Position the engine on the inner fan housing the holes in the engine and fan housing must be in alignment. 96RA04 TG : Insert the screws (arrows) and tighten them down firmly. : Pull the complete engine () out of the blower housing. Install the blower wheel, b. BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 9

21 Cylinder removed To remove the flywheel, the crankshaft has to be blocked by resting the piston on the wooden assembly block. Remove the engine, b RA3 TG 96RA03 TG Fit the short circuit and ground wires in the retainers (arrow). : Push the fuel suction hose () and fuel return hose () onto the stubs (arrows) on the connector. : Attach the ground wire () to the guide (arrow) and push it firmly onto the connector tag (). 96RA09 TG Install the air filter, b 0. Reassemble all other parts in the reverse sequence. Tightening torques, b Cylinder Removing and Installing Before removing the cylinder, decide whether or not the crankshaft has to be removed as well. Remove the muffler (), b 5. Remove the ignition module (), b 6.. Remove the flywheel (3), b RA03 TG Cylinder installed To remove the flywheel, the crankshaft has to be blocked by inserting the locking strip in the spark plug hole. 998RA3 AM : Take out the screws (arrows). 96RA030 TG Remove the spiral housing (). : Attach the short circuit wire () to the guide (arrow) and push it firmly onto the ignition module's connector tag (). Install the throttle rod, b BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

22 3 96RA033 TG 998RA34 AM 998RA37 AM Prepare the puller () : Take out the cylinder screws (arrows). Inspect and clean the sealing face (arrow), b 3 : Fit the No. jaws () : Screw the bushing (3) onto the puller's spindle. The sealing face must be in perfect condition. Always replace components with damaged sealing faces, b 4.5. Installing 998RA35 KN Always use a new cylinder gasket when re-installing the cylinder. 3 : Carefully lift the cylinder () away. 998RA33 AM Do not use pointed or sharp-edged tools for this job. : Apply the puller () with the jaws under the crankcase ribs (arrows) and line up the spindle () so that the bushing (3) is centered on the engine pan. : Turn the spindle clockwise until the puller sits tightly. Do not overtighten the spindle because the jaws may slip off or damage the crankcase ribs. Check the cylinder and replace if necessary : Remove the cylinder gasket (). 998RA36 AM Line up the cylinder gasket () so that the tab and cutouts (arrows) match the contours of the crankcase. : Place the cylinder gasket () in position. 998RA38 AM BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

23 Check the sealing faces on the cylinder intake and exhaust ports. Apply the clamping strap () so that the piston rings do not project beyond the cylinder wall. Inspect the spacer flange () and replace it if necessary even very minor damage can result in engine running problems, b RA040 TG The sealing faces must be in perfect condition. If the sealing faces are damaged, install a new cylinder. Inspect the piston and piston rings and replace if necessary, b RA046 TG In a new cylinder is installed, the spacer flange must be transferred from the old cylinder. : Take out the screws (arrows). Remove the spacer flange (). 998RA39 AM : Align the cylinder so that the recess in the cylinder engages the lug on the crankcase (arrows). : Slide the wooden assembly block () between the piston and crankcase. 998RA4 AM : Remove the gasket (). 96RA04 TG Lubricate the piston, piston rings and cylinder wall with oil, b 3 998RA40 AM While sliding the cylinder over the piston, hold the clamping strap tightly around the piston so that the rings do not project they might otherwise break. : Slide the cylinder over the piston, the clamping strap moves downwards at the same time. : Use the clamping strap () to compress the rings around the piston. 96RA04 TG Check correct installed position of rings, b 5.8. : Inspect and clean the sealing face (arrow) and remove any gasket residue, b 3 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

24 5.6 Crankshaft 5.6. Removing and Installing : Remove the clamping strap () and wooden assembly block (). 998RA4 AM Remove the engine, b 5.4 The puller is not necessary for removal of the crankshaft. Remove the flywheel, b 6.5 Remove the cylinder, b 5.5 Remove the piston, b 5.8 : Pull the oil seals (arrows) off the crankshaft stubs. 998RA44 AM Make sure the cylinder gasket is properly seated. Check the crankshaft and ball bearings and replace if necessary, b RA050 TG Push the cylinder fully home. : Insert the screws (arrows) to hold the cylinder and gasket in position.. Tighten down the screws firmly in a crosswise pattern. Tightening torques, b 3.4 Remove the puller. Install the spacer flange, b 0.7 Install the muffler, b 5. Install the ignition module, b 6.. Reassemble all other parts in the reverse sequence. 998RA43 AM : Loosen the engine pan () at the lug (arrow). Remove the engine pan. : Release the crankshaft from the bearing seats (arrows) and take it out of the crankcase. 96RA05 TG Inspect the crankcase and sealing faces (arrows) for the engine pan and cylinder, clean and remove gasket residue if necessary, b 3 The sealing faces must be clean and in perfect condition. Always replace components with damaged sealing faces. 96RA053 TG BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 3

25 96RA54 TG 96RA056 TG 96RA059 TG Check the spacer flange () and replace if necessary, b 0.7 In a new cylinder is installed, the spacer flange must be transferred from the old cylinder always install a new gasket, b 0.7. Installing Position the crankcase () so that the bearing seats face up. : Before fitting the crankshaft in the crankcase, line it up so that the straight stub () is at the same side as the recesses (arrows). Inspect and clean the sealing faces on the engine pan and remove any gasket residue, b 3 The sealing faces must be clean and in perfect condition. Always replace components with damaged sealing faces. : Apply sealant to the groove in the sealing face, b 3 : Fit the installing sleeve () : Push the new oil seals, open side facing the ball bearings (arrows), on to the crankshaft stubs. 998RA45 AM Position the crankshaft, connecting rod first, in the crankcase. : Place the crankshaft with bearings and oil seals in the crankcase, making sure the oil seals are properly seated against the stops (arrows). 96RA058 TG Make sure the sealant does not project into the engine pan. Line up the engine pan () so that the lug () is on the same side as the crankcase contour (arrow). 96RA060 TG : Place the engine pan () on the crankcase sealing face. Press the engine pan carefully into position so that the sealant is evenly distributed. 4 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

26 3 5.7 Bearings / Crankshaft Remove the crankshaft, b 5.6 Pull off the oil seals, b RA06 TG 96RA06 TG : Insert the cylinder base screws in the holes (arrows) to hold the engine pan in position. 3 Prepare the puller () : Fit the No. jaws () : Screw the bushing (3) onto the puller's spindle. 96RA033 TG : Apply the puller () with the jaws under the crankcase ribs (arrows) and line up the spindle () so that the bushing (3) is centered on the engine pan. : Turn the spindle clockwise until the puller sits tightly. Do not overtighten the spindle because the jaws may slip off or damage the crankcase ribs. Clean the crankshaft stubs, b 3 Install the piston, b 5.8 Install the cylinder, b 5.5 Remove the puller. Install the engine, b 5.4 Reassemble all other parts in the reverse sequence. : Pull the ball bearing () off the tapered crankshaft stub. : Pull the ball bearing () off the straight crankshaft stub. 96RA064 TG 96RA065 TG Take care not to damage the crankshaft stubs. BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 5

27 96RA066 TG 96RA068 TG 96RA069 TG : The crankshaft (), connecting rod () and needle bearing form an inseparable unit. It must always be replaced as a complete unit. When fitting a replacement crankshaft, always install new ball bearings and oil seals. Before installing, clean the crankshaft, b 3 Use a firm base () to protect the crankshaft. : Apply a suitable sleeve () to the inner race of the ball bearing at the ignition side and press it home as far as stop. Lubricate the needle bearing with oil. Install the piston, b 5.8 Fit new oil seals and install the crankshaft, b 5.6. Install the engine, b 5.4 Tightening torques, b 3.4 Reassemble all other parts in the reverse sequence. 5.8 Piston : Use a suitable tool to grip the hookless snap ring at the recess (arrow) and ease it out. : Apply assembly drift () , small diameter first, to the ignition side of the piston. 998RA46 AM 96RA067 TG Remove the engine, b 5.4 Remove the cylinder, b 5.5 Use a firm base () to protect the crankshaft. : Apply a suitable sleeve () to the inner race of the ball bearing at the blower side and press it home as far as stop. The piston has only one snap ring. It is fitted at the blower side (straight crankshaft stub). 998RA47 AM : Use the assembly drift () to push the piston pin () out of the piston. 6 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

28 If the piston pin is stuck, release it by tapping the end of the drift lightly with a hammer. Hold the piston steady during this process to ensure that no jolts are transmitted to the connecting rod. 998RA48 AM : Line up the piston as shown so that the arrow (arrow) on the piston crown faces the crankcase lug () and the straight crankshaft stub () is on the right. : Place the piston on the connecting rod. 998RA49 AM : Fit the piston pin () on the assembly drift () and slide it into the piston. 998RA5 AM : Remove the piston () from the connecting rod. Inspect the piston and replace it if necessary. Inspect the piston rings and replace if necessary, b RA077 TG 998RA50 AM : Remove the sleeve () from the installing tool () RA073 TG : Push the assembly drift () , small diameter first, through the piston and small end (needle cage). The previous sleeve () may also be used. The new sleeve () has a 0 chamfer for better security in the piston bore. : Pull out the needle cage (), check it and replace if necessary, b 3 Lubricate the needle cage with oil and push it into the connecting rod. BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 7

29 Use a suitable base (wooden board). 533RA8 TG 96RA08 TG : Attach the snap ring () to the magnet () so that the ring gap is on the flat side of the tool's shank (arrow). 3 : Remove the sleeve and push it on to the other end of the shank as far as stop. The inner pin (arrow) must again point toward the flat face. 533RA3 TG Fit the snap ring () so that its gap (arrow) points down it must not be near the recess (). Check installed position of snap ring. : Push the slotted diameter of the sleeve () over the magnet and snap ring. The inner pin () must point towards the flat face (3) of the tool's shank. 96RA078 TG Install the snap ring at the blower side of the piston. : Apply the installing tool with the sleeve s taper against the piston boss, hold the piston steady, center the tool shank exactly and press home until the snap ring slips into the groove. 998RA5 AM Inspect the piston rings and replace if necessary, b 5.8. Install the cylinder, b 5.5 Install the engine, b 5.4 Tightening torques, b 3.4 Reassemble all other parts in the reverse sequence. 998RA54 AM 96RA79 TG Make sure the tool is held square on the piston pin axis. : Press the installing tool downwards into the sleeve until the magnet butts against the end of the guide slot. 8 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

30 5.8. Piston Rings Remove the piston, b 5.8 Remove the piston rings from the piston. 96RA083 TG 96RA085 TG 96RA084 TG : Position the piston rings so that the radii at the ring gap meet at the fixing pin in the piston groove (arrows). Install the piston, b 5.8 : Position the new piston rings in the groove so that the radii (arrows) at the ring gaps face upwards. : Use a piece of old piston ring to scrape the grooves clean Piston Rings Remove the piston, b 5.8 Remove the piston rings from the piston. 96RA085 TG 96RA084 TG : Position the piston rings so that the radii at the ring gap meet at the fixing pin in the piston groove (arrows). : Position the new piston rings in the groove so that the radii (arrows) at the ring gaps face upwards. : Use a piece of old piston ring to scrape the grooves clean. 96RA083 TG Check correct installed position of the piston rings (arrows). Install the piston, b 5.8 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 9

31 6. Ignition System Exercise extreme caution when troubleshooting and carrying out maintenance or repair work on the ignition system. The high voltages which occur can cause serious or fatal accidents. Testing in the workshop is limited to a spark test. A new ignition module must be installed if no ignition spark is obtained (after checking that wiring and stop switch are in good condition), b 6... Troubleshooting on the ignition system should always begin at the spark plug, b 4.3 Ignition timing is fixed and cannot be adjusted during repair work. 96RA090 TG Remove the fan housing, b 7. Since there is no mechanical wear in these systems, ignition timing cannot get out of adjustment during operation. : Take out the screw (arrow). Remove the connector tag (). 6.. Removing and Installing Remove the fan housing, b 7. : Take out the screw () and washer. 96RA086TG The electronic (breakerless) ignition system basically consists of an ignition module () and flywheel (). 6. Ignition Module 96RA088 TG : Remove the ignition module (). 96RA09 TG : Pull boot () off the spark plug. The ignition module accommodates all the components required to control ignition timing. There are two electrical connections on the coil body: High voltage output () with ignition lead Connector tag () for the short circuit wire 96RA087 TG : Disconnect the short circuit wire () and ground wire (). 96RA0 TG The ignition module () and ignition lead () form a unit. Check the ignition module () and replace if necessary 96RA09 TG 30 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

32 N S 96RA093 TG 96RA095 TG 96RA089 TG : Remove the insulator (). Check the insulator and replace if necessary. Check the spark plug boot and replace if necessary, b 6.4 Troubleshooting, b 4.3 Position the insulator () so that the connecting bar () points towards the carburetor. 96RA094 TG : Place the ignition module () in position so that the ignition lead () faces the muffler and insert the screw (arrow) with washer do not tighten down yet. : Fit the connector tag () and insert the screw (arrow) do not tighten down yet. 96RA096 TG Push the ignition module () back the flywheel must turn freely. The setting gauge is not shown in the illustration. : Hold the setting gauge and rotate the flywheel until the magnet poles (arrows) are next to the ignition module. Press the ignition module against the setting gauge. Tighten down the screws firmly. Tightening torques, b 3.4 Remove the setting gauge. Check operation rotate the flywheel and make sure it does not touch the ignition module. : Attach the lugs (arrows) of the insulator () to the bosses. Push the ignition module () back : Slide the setting gauge () between the arms of the ignition module and the flywheel magnet. 96RA097 TG : Fit the ground wire (wide flag terminal) and then the short circuit wire (narrow flag terminal) in the guide (arrow). 96RA098 TG BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 3

33 96RA099 TG 3 65RA83 TG 3 96RA00 TG : Connect the ground wire () and short circuit wire (). Push the boot onto the spark plug. Reassemble all other parts in the reverse sequence. 6. Ignition Timing Ignition timing is fixed and cannot be adjusted during repair work. Since there is no mechanical wear in these systems, ignition timing cannot get out of adjustment during operation. 6.3 Testing the Ignition Module To test the ignition module, use either the ZAT 4 ignition system tester or the ZAT 3 ignition system tester The ignition test refers only to a spark test, not to ignition timing. Using the ZAT 4 ignition tester Before starting the test, install a new spark plug in the cylinder and tighten it down firmly. Tightening torques, b 3.4 : Connect spark plug boot to the input terminal (). Push the tester s output terminal (3) on to the spark plug. High voltage risk of electric shock. : Crank the engine quickly with the rewind starter and check spark in the tester s window (). The engine may start and accelerate during the test. If a spark is visible, the ignition system is in order. If no spark is visible in the window (), check the ignition system with the aid of the troubleshooting chart, b 6.7 Using the ZAT 3 ignition tester Before starting the test, install a new spark plug in the cylinder and tighten it down firmly. Tightening torques, b 3.4 Connect spark plug boot to the terminal (). : Attach the ground terminal () to the spark plug. : Use adjusting knob (3) to set the spark gap to about mm. 3 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

34 RA85 TG 96RA0 TG 96RA03 TG While using the ZAT 3, hold it only by the handle (4) or position it in a safe place. Keep fingers or other parts of your body at least cm away from the spark window (3), high voltage connection (), ground connection (5) and the ground terminal (). High voltage risk of electric shock. Crank the engine quickly with the rewind starter and check spark in the tester s window (3). : Use suitable pliers to pull the leg spring out of the spark plug boot. Unhook the leg spring from the ignition lead. Pull the boot off the ignition lead. 67 mm Coat inside of spark plug boot with STIHL Press Fluid, b 3 : Hold the ignition lead and leg spring together and push them into the spark plug boot. The engine may start and accelerate during the test. If a spark is visible, the ignition system is in order. If no spark is visible in the window (3), check the ignition system with the aid of the troubleshooting chart, b Spark Plug Boot The ignition module () and ignition lead () form a unit. A new ignition module must be installed if the ignition lead is damaged. Remove the fan housing, b 7. Pull the boot off the spark plug. Use a pointed tool to pierce the center of the new ignition lead s insulation, about 67 mm from the end of the lead. : Pinch the hook of the leg spring into the center of the lead (arrow). 96RA0 TG 65RA88 TG : Make sure the leg spring (arrow) locates properly inside the spark plug boot. Do not use either graphite grease or silicone insulating paste. Reassemble all other parts in the reverse sequence. 96RA04 TG BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 33

35 a 96RA35 TG b The rubber lip of the spark plug boot must completely seal the opening (arrows) in the fan housing. The puller can be modified as shown above this does not affect its use in other machines. 6.5 Flywheel : Turn the screw end of the puller to a diameter of 'b' = 6 mm and depth of 'a' = 0 mm. Remove the fan housing, b 7. Unscrew the spark plug. Use locking strip () to block the piston, b RA33 TG : Screw the puller () clockwise on to the crankshaft as far as stop, then back it off a /4 turn. Tap the end of the puller a few times to release the flywheel take care not to damage the crankshaft stub or ball bearing. Unscrew the puller and remove the flywheel. 96RA06 TG 96RA07 TG 96RA09 TG The flywheel and magnet poles (arrows) must not be damaged or have turned blue. Replace flywheel if necessary. Before assembly, degrease the bore in the flywheel hub and the crankshaft stub, b 3. 96RA08 TG : Make sure the key (arrow) engages the slot in the crankshaft stub. Check the air gap between the ignition module and flywheel and adjust if necessary, b 6.. Reassemble all other parts in the reverse sequence. Tightening torques, b RA0 TG : Unscrew the flywheel nut (arrow). If the flywheel is stuck, use a puller. 34 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

36 6.6 Short Circuit Wire 6.6. Testing 96RA TG To locate the fault, test the wires for continuity and check insulation for damage. If the wires are in order, check operation of stop switch, b 6.7 If no fault can be found, check the ignition system with the aid of the troubleshooting chart, b 6.7 Check ground wire for continuity. Reassemble in the reverse sequence Removing and Installing Removal (all models) Remove the fan housing, b 7. Remove the throttle rod, b 0.6 Remove the throttle trigger, b 9.3, b 9.4 If the spark plug, ignition lead and spark plug boot are in order, check the short circuit wire and stop switch. Remove the fan housing, b 7. : Disconnect the short circuit wire (). Connect the ohmmeter to ground (arrow) and the short circuit wire (). Set the stop switch to "0" and hold it in that position. The resistance measured must be about 0 Ω. If it is much higher, the reason may be the stop switch or the wire. Damaged parts must be replaced, b 6.6.4, b Set the stop switch to "F". The resistance measured must be infinitely high. If not, fit a new short circuit wire or stop switch, b 6.6., b Models SH 56, SH 56 C, BG 56, BG 56 C, BG 66 Separate short circuit and ground wires are installed in these machines and may be replaced individually in case of damage. Models SH 86, SH 86 C, BG 66 C, BG 86, BG 86 C Short circuit and ground wires are combined in a wiring harness. The complete wiring must be replaced if either wire is damaged. When cleaning the machine, make sure wires are not accidentally disconnected. The short circuit and ground wires are non-interchangeable, i.e. the short circuit wire is equipped with narrow flag terminals (one is insulated) and the ground wire has wide flag terminals (with additional wire at one end). : Pull boot () off the spark plug. : Disconnect the short circuit wire () and ground wire (). Pull the short circuit and ground wires out of the guide (arrow). 96RA088 TG 96RA TG BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 35

37 3 96RA3 TG 96RA6 TG : Pull the wires out of the guides (arrows). 96RA8 TG : Disconnect the short circuit wire () and ground wire () from the stop switch (3). Position the stop switch () so that the "0" on the switch points in the direction of the blower tube. Models SH 56, SH 56 C, BG 56, BG 56 C, BG 66 Check the individual parts and replace if necessary. A faulty ground wire may impair or prevent operation of the short circuit wire. The ground wire must therefore be tested for good contact and continuity. : Slide the stop switch () into the guides (arrows) the flag terminals must point inside the housing. 96RA4 TG Installing : Pull the ground wire () off the pin. : Pull out the stop switch (). : Push the ground wire terminal () on to the pin (). 96RA9 TG 96RA7 TG : Route the ground wire () past the rib (arrow). Push the flag terminals firmly on to the connector tags of the stop switch. : Pull the ground and short circuit wires out of the guides (arrows). Remove the wires with the stop switch. 96RA5 TG : Fit the short circuit wire () with the insulated flag terminal on the narrow connector tag. : Fit the ground wire () with additional wire on the wide connector tag. The flag terminals must point to the right with the switch in the position shown (small arrow). 36 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

38 A faulty ground wire may impair or prevent operation of the short circuit wire. The ground wire must therefore be tested for good contact and continuity. 96RA0 TG 96RA3 TG Installing : Push the ground wire () into the guides (arrows) first, then the short circuit wire (). Position the wires next to one another without crossing over. : Pull out the stop switch (). 96RA6 TG : Fit the short circuit wire () and ground wire () in the guide (arrow). 96RA TG : Pull the wiring harness out of the guides (arrows). Remove the wiring harness with the stop switch. 96RA4 TG Push the flag terminals firmly on to the connector tags of the stop switch. : Fit the short circuit wire () with the insulated flag terminal on the narrow connector tag. : Fit the ground wire () with additional wire on the wide connector tag. The flag terminals must point to the left with the switch in the position shown (small arrow). Models SH 86, SH 86 C, BG 66 C, BG 86, BG 86 C 3 96RA5 TG : Pull the ground wire () off the pin. : Pull the ground wire () out of the guides (arrows). 96RA TG : Disconnect the short circuit wire () and ground wire () from the stop switch (3). Check the wiring harness and stop switch and replace if necessary. BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 37

39 All Models Position the stop switch () so that the "0" on the switch points towards the inside of the housing. : Slide the stop switch () into the guides (arrows) the flag terminals must point in the direction of the blower tube. 96RA7 TG Lay the wiring harness over the dome () of the spring mount. : Push the protective tube () of wiring harness into the retainers (arrows). 96RA9 TG : Fit the ground wire (wide flag terminal) and then the short circuit wire (narrow flag terminal) in the guide (arrow). 96RA098 TG : Push the ground wire terminal () on to the pin (). : Push the ground wire () into the guides (arrows). 96RA8 TG : Push the wiring harness, ground wire first, into the guides (arrows). Position the wires next to one another without crossing over. 96RA30 TG : Connect the ground wire () and short circuit wire (). Reassemble all other parts in the reverse sequence. Tightening torques, b RA TG 96RA099 TG : Fit the short circuit wire () and ground wire () in the guide (arrow). 38 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

40 6.6.3 Ground Wire A faulty ground wire may impair or prevent operation of the short circuit wire. Models SH 56, SH 56 C, BG 56, BG 56 C, BG 66 Separate short circuit and ground wires are installed. The ground wire must be replaced if it is damaged. Models SH 86, SH 86 C, BG 66 C, BG 86, BG 86 C Short circuit and ground wires are combined in a wiring harness. The complete wiring must be replaced if either wire is damaged. Check for contact and continuity and replace the wiring harness if necessary, b 6.6. Remove and install the wires or wiring harness, b Stop Switch 96RA3 TG Remove the stop switch (), b 6.6. Test the stop switch and replace if necessary Set the stop switch to "0" = connection Set the stop switch to "F" = no connection Reassemble in the reverse sequence. BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 39

41 6.7 Ignition System Troubleshooting Engine does not run Stop Switch: in position "F"? Check the spark plug: Smeared with oil, black? Sooted? Electrode gap correct? Contacts shorted? Clean or replace the plug b 6.3 Check the spark plug boot: Firmly seated on plug (leg spring)? Leg spring hook in center of ignition lead? Boot damaged? If necessary, install new spark plug boot and/ or leg spring, b 6.4 Test ignition system: with ZAT 3 or ZAT 4 (use ZAT 3 as main spark gap see TI 3.94), b BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

42 Ignition spark? yes no Air gap: Check ignition module/flywheel, reset if necessary, b 6.. Check the flywheel: Have pole shoes turned blue? Install new flywheel if necessary, b 6.5 Check ground and short circuit wires: Wire damaged? Connectors firmly seated? Check continuity, replace wires or wiring harness if necessary, b 6.6. Check the ignition lead: Severe chafing? Spark plug boot: Holes/cracks? Resistance: spark plug boot to ground: spec..5 kω If necessary, install new spark plug boot and/or ignition lead with module, b BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 4

43 3 Check operation of stop switch: Function of stop switch: Position "F" = no connection Position "0" = connection Install new stop switch if necessary, b Ignition spark? yes no Ignition Module b 6.. yes Machine runs no Machine runs trouble-free, no further action necessary Look for fault in fuel system or carburetor Check engine for leaks Check position of flywheel on crankshaft, b 5., b BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86

44 7. Rewind Starter 7. General 7. Removing and Installing If the action of the starter rope becomes very stiff and the rope rewinds very slowly or not completely, 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 a standard solventbased degreasant (containing no chlorinated or halogenated hydrocarbons) to the rewind spring. : Take out the screws (arrows). Remove the fan housing (). 96RA3 TG The rubber lip of the spark plug boot must completely seal the opening (arrows) in the fan housing. 7.3 Pawl 96RA35 TG Carefully pull out the starter rope several times and allow it to rewind until its normal smooth action is restored. Before installing, lubricate the rewind spring and starter post with STIHL special lubricant. If clogged with dirt or pitch, the entire starter mechanism, including the rewind spring, must be removed and disassembled. Take particular care when removing the spring. Clean all components, b 3 Models with ErgoStart Relieve tension of rewind spring, b 7.4 : Position the fan housing () so that the guide lugs (arrows) engage the blower housing. 96RA3 TG Remove the fan housing, b 7. : Carefully ease the spring clip () off the starter post the rewind spring may pop out and uncoil. 96RA34 TG 96RA33 TG : Insert the screws (arrows) and check the position of the fan housing. Tightening torques, b 3.4 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 43