Stihl BG 86 Power Tool Service Manual

STIH) STIHL BG 56, 66, 86, SH 56, 86 2008-01

1 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 q © ANDREAS STIHL AG & Co. KG, 2008 RA_296_01_01_01 1. Introduction 2 2. Safety Precautions 3 3. Specifications 4 3.1 Engine 4 3.2 Fuel System 4 3.3 Ignition System 4 3.4 Tightening Torquese 5 4. Troubleshooting 7 4.1 Rewind Starter 7 4.2 Fan 8 4.3 Ignition System 9 4.4 Carburetor 11 4.5 Engine 14 5. Engine 15 5.1 Muffler / Spark Arresting Screen 15 5.2 Leakage Test 16 5.2.1 Preparations 16 5.2.2 Vacuum Test 17 5.2.3 Pressure Test 17 5.3 Oil Seals 18 5.4 Removing and Installing the Engine 19 5.5 Removing and Installing the Cylinder 21 5.6 Crankshaft 24 5.6.1 Removing and Installing 24 5.7 Bearings / Crankshaft 27 5.8 Piston 28 5.8.1 Piston Rings 30 6. Ignition System 31 6.1 Ignition Module 31 6.1.1 Removing and Installing 31 6.2 Ignition Timing 33 6.3 Testing the Ignition Module 33 6.4 Spark Plug Boot 34 6.5 Flywheel 35 6.6 Short Circuit Wire 36 6.6.1 Testing 36 6.6.2 Removing and Installing 37 6.6.3 Ground Wire 40 6.6.4 Stop Switch 40 6.7 Ignition System Troubleshooting 41 7. Rewind Starter 44 7.1 General 44 7.2 Removing and Installing 44 7.3 Pawls 44 7.4 ErgoStart 45 7.5 Rope Rotor 46 7.6 Starter Rope / Grip 47 7.7 Tensioning the Rewind Spring 49 7.8 Replacing the Rewind Spring 50 8. Repairing AV System SH 86, 86 C, BG 66C, 86, 86 C 52 8.1 Removing and Installing 52 8.2 Handle SH 86, 86 C, BG 66C, 86, 86 C 53 9. Control Levers 55 9.1 Switch Positions 55 9.2 Setting Lever SH 86, 86 C, BG 66C, 86, 86 C 55 9.3 Throttle Trigger SH 56, 56 C, BG 56, 56 C, 66 56 9.4 Throttle Trigger SH 86, 86 C, BG 66C, 86, 86 C 57 10. Fuel System 59 10.1 Air Filter 59 10.2 Baffle / Filter Housing 60 10.3 Removing and Installing the Carburetor 61 10.3.1 Leakage test 62 10.4 Servicing the Carburetor 62 10.4.1 Metering Diaphragm / Manual Fuel Pump 62 10.4.2 Inlet Needle 64 10.4.3 Pump Diaphragm 64 10.4.4 Throttle Lever / Rotary Knob 66 10.4.5 Adjusting Screws 67 10.5 Adjusting the Carburetor 68 10.5.1 Basic Setting 68 10.5.2 Standard Setting 69 10.6 Throttle Rod 70 10.7 Removing and Installing the Spacer Flange 71 10.8 Tank Vent 72 10.8.1 Testing 72 10.8.2 Removing and Installing 73 10.9 Fuel Intake 73 10.9.1 Pickup Body 73 10.9.2 Fuel Hoses 74 10.9.3 Fuel Tank Cap 75 11. Blower and Vacuum Attachment 76 11.1 Intake Screen 76 11.2 Fanwheel 77 11.3 Removing and Installing the Fan Housing SH 56, 56 C, BG 56, 56 C, 66 78 11.3.1 Removing and Installing the Fan Housing SH 86, 86 C, BG 66C, 86, 86 C 78 11.3.2 Removing and Installing the Handle Housing SH 86, 86 C, BG 66C, 86, 86 C 79 11.4 Blower Tube BG Models 79 11.5 Elbow SH Models 80 11.6 Suction Tube SH Models 80 12. Special Servicing Tools 81 13. Servicing Aids 83 Contents

2 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 1. 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 troubleshooting charts for all assemblies and systems in this manual and the "STIHL Service Training System". 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 as 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 4.2 = Reference to another chapter, i.e. chapter 4.2 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.

3 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 2. Safety Precautions If the engine is started up in the course of repairs or maintenance work, observe all local and country- specific 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.

4 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 3. Specifications 3.1 Engine BG 56, SH 56 BG 66, BG 66 C BG 86, SH 86 Displacement: 27.2 cm 3 27.2 cm 3 27.2 cm 3 Bore: 34 mm 34 mm 34 mm Stroke: 30 mm 30 mm 30 mm Engine power to ISO 7293: 0.70 kW (1.0 bhp) 0.60 kW (0.8 bhp) 0.8 kW (1.1 bhp) Max. permissible speed (with nozzle): 6800 rpm 5800 rpm 7200 rpm Idle speed: 2500 rpm 2500 rpm 2500 rpm Engine leakage test under vacuum: 0.5 bar at gauge pressure: 0.5 bar 3.2 Fuel System Carburetor leakage test at gauge pressure: 0.8 bar Operation of tank vent at gauge pressure: 0.5 bar Fuel: as specified in instruction manual 3.3 Ignition System Air gap between ignition module and fanwheel: 0.15 ... 0.30 mm Spark plug (suppressed): NGK CMR 6 H Electrode gap: 0.5 mm

5 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 3.4 Tightening Torquese 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 5x18 Fan housing, outer/inner 3.0 Screw D 5x24 Fan housing, inner/crankcase 8.0 Screw D 5x24 Fan housing, inner/engine pan 8.0 Screw D 5x24 Fan housing, inner/cylinder 8.0 Nut M 8x1 L Fanwheel/crankshaft 17.0 Screw P 5x18 Handle/cover/plug 3.0 Screw P 5x18 Handle/handle frame/plug 3.0 Screw P 5x18 Handle molding/fran housing, inner 3.0 Screw P 5x18 Handle molding/handle/handle frame/ plug 3.0 Screw D 5x60 Engine pan/crankcase/cylinder 9.0 Screw D 5x20 Fan housing/spiral housing 6.0 Screw D 5x20 Muffler/cylinder 9.0 Nut M 8x1 Flywheel/crankshaft 17.0 1) Screw D 5x20 Spiral housing/crankcase 6.0 Screw D 5x20 Spiral housing/engine pan 6.0 M 10x1 Spark plug 12.0 Screw D 4x18 Ignition module/cylinder 3.5 Screw D 5x20 Spacer flange/cylinder 6.0

6 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 Remarks: 1) 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.

7 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 4. Troubleshooting 4.1 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 little standard solvent-based degreasant (containing no chlorinated or halogenated hydrocarbons), then pull rope carefully several times until normal action is restored

8 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 4.2 Fan Always switch off the engine before working on the fan. Condition Cause Remedy No suction Fanwheel loose Tighten down fanwheel nut firmly Fanwheel blocked Clean fan housing Poor suction Catcher bag full Empty the catcher bag Fan outlet blocked Clean fan housing and outlet Fanwheel worn or too many blades broken Fit a new fanwheel Poor blowing performance Intake screen very dirty Clean intake screen and fan housing Fanwheel loose Tighten down fanwheel nut firmly Fanwheel worn or too many blades broken Fit a new fanwheel Leaves are not properly shredded Shredder blade loose or worn Tighten down or replace the shredder blade

9 BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86 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 is damaged 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. Faulty insulation or break in ignition lead or short circuit wire. Check ignition lead/ignition module and replace ignition module if necessary. Check operation of spark plug. Clean the spark plug or replace if necessary. Also refer to carburetor and engine troubleshooting.

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Stihl BG 86 Power Tool Service Manual

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