Stihl MS 880 Service Manual

STIH) STIHL MS 780, 880 2009-08

1 MS 780, MS 880 q © ANDREAS STIHL AG & Co. KG, 2009 RA_550_00_01_02 1. Introduction 3 2. Safety Precautions 5 3. Specifications 6 3.1 Engine 6 3.2 Fuel System 6 3.3 Ignition System 6 3.4 Chain Lubrication 6 3.5 Tightening Torquese 7 4. Troubleshooting 9 4.1 Clutch 9 4.2 Chain Drive, Chain Brake, Chain Tensioner 10 4.3 Chain Lubrication 11 4.4 Rewind Starter 12 4.5 Ignition System 13 4.6 Carburetor 15 4.7 Engine 18 5. Saw Chain / Guide Bar 19 5.1 Spiked Bumper / Chain Catcher 19 6. Clutch 20 6.1 Clutch Drum 22 7. Chain Brake 23 7.1 Checking Operation 23 7.2 Removing and Installing the Brake Band 23 7.3 Brake Lever 25 7.4 Cam Lever 26 7.5 Pins 27 7.6 Chain Tensioner 28 7.7 Bar Mounting Studs 29 8. Engine 30 8.1 Muffler with Spring Clip/ Spark Arresting Screen 30 8.2 Screw Mounted Muffler / Spark Arresting Screen 32 8.3 Leakage Test 34 8.3.1 Preparations 34 8.3.2 Vacuum Test 36 8.3.3 Pressure Test 36 8.4 Oil Seals 37 8.5 Carburetor Box Cover 38 8.6 Removing and Installing the Shroud 39 8.7 Cylinder 40 8.8 Crankshaft 43 8.8.1 Removing and Installing 43 8.8.2 Bearings / Crankcase 48 8.9 Piston 50 8.9.1 Removal 50 8.9.2 Installing 51 8.10 Piston Rings 52 8.11 Decompression Valve 53 9. Ignition System 54 9.1 Ignition Timing 54 9.2 Ignition Module 54 9.2.1 Removing and Installing – Version with two mounting screws 54 9.2.2 Removing and Installing – Version with three mounting screws 56 9.3 Testing the Ignition Module 59 9.4 Spark Plug Boot / Ignition Lead 60 9.5 Flywheel 61 9.6 Short Circuit Wire 63 9.6.1 Testing 63 9.6.2 Removing and Installing – Version with three mounting screws 63 9.6.3 Removing and Installing – Version with cable channel 66 9.6.4 Ground Wire 68 9.6.5 Contact Spring 69 9.7 Ignition System Troubleshooting 70 10. Rewind Starter 73 10.1 General 73 10.2 – Removing and Installing 73 10.3 Pawls 74 10.4 Rope Rotor 74 10.5 Starter Rope / Grip 75 10.6 Tensioning the Rewind Spring 77 10.7 Replacing the Rewind Spring 77 11. Servicing the AV System 79 11.1 Annular Buffer on Oil Tank at Clutch Side 79 11.2 Annular Buffer on Oil Tank at Ignition Side 80 11.3 Annular Buffer at Clutch Side 80 11.4 Annular Buffer at Ignition Side 81 11.5 Stop Buffer at Ignition Side 81 11.6 Stop Buffer on Ignition Module 82 11.7 Stop Buffer at Clutch Side 82 11.8 Handlebar 83 12. Control Levers 84 12.1 Switch Shaft 84 12.1.1 Removing and Installing 84 12.1.2 Throttle Trigger/ Interlock Lever 86 12.1.3 Choke and Throttle Rods with Levers 87 13. Chain Lubrication 90 13.1 Pickup Body 90 13.2 Oil Suction Hose 90 13.3 Removing and Installing the Oil Pump 91 13.3.1 Spur Gear – Removing and Installing 92 13.4 Valve 93 Contents

2 MS 780, MS 880 Contents 14. Fuel System 94 14.1 Air Filter 94 14.2 Removing and Installing the Filter Base 94 14.3 Carburetor – Removing and Installing 94 14.4 Leakage test 97 14.5 Servicing the Carburetor Tillotson Carburetor 97 14.5.1 Metering Diaphragm 97 14.5.2 Inlet Needle 98 14.5.3 Fixed Jet 99 14.5.4 Pump Diaphragm 99 14.5.5 Choke Shaft / Choke Shutter 100 14.5.6 Throttle Shaft / Throttle Shutter 102 14.5.7 Adjusting Screws 103 14.6 Servicing the Carburetor – Walbro Carburetor 105 14.6.1 Metering Diaphragm 105 14.6.2 Inlet Needle 106 14.6.3 Fixed Jet 107 14.6.4 Pump Diaphragm 107 14.6.5 Choke Shaft / Choke Shutter 108 14.6.6 Throttle Shaft / Throttle Shutter 110 14.6.7 Adjusting Screws 111 14.7 Adjusting the Carburetor 113 14.7.1 Basic Setting 113 14.7.2 Standard setting 114 14.7.3 Intake Manifold – Removing and Installing 115 14.7.4 Impulse Hose 116 14.8 Tank Vent 117 14.8.1 Testing 117 14.8.2 Removing and Installing 118 14.9 Fuel Intake 118 14.9.1 Pickup Body 118 14.9.2 Fuel Hose 118 14.9.3 Tank Housing – Removing and Installing 119 15. Special Servicing Tools 121 16. Servicing Aids 123

3 MS 780, MS 880 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 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 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 @ 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. Servicing and repairs are made considerably easier if the machine is mounted to assembly stand (3) 5910 890 3100. To do this, secure the mounting plate (2) 5910 850 1650 to the assembly stand with two screws (1) and washers. The screws must not project since they, depending on the machine, may damage housings when the machine is clamped in position. The above operation is not necessary with the new assembly stand 5910 890 3101 since the mounting plate is already fitted. 1 2 3 219RA000 TG

4 MS 780, MS 880 Engage the bar mounting studs in the outer bores in the mounting plate and secure the saw in position with the nuts (arrows). Preparations for servicing Remove the chain sprocket cover, saw chain and guide bar before carrying out repairs or mounting the machine to the assembly stand. Always use original STIHL replacement parts. They can be identified by the STIHL part number, the { logo and the STIHL parts symbol K 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. 216RA000 TG

5 MS 780, MS 880 2. Safety Precautions If the power tool 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. Fuel system – hose barb connectors Pull off or push on fuel hoses in line with the connector, preferably by hand, to ensure the tightness of the fuel system. Avoid damaging the hose barb – do not use sharp-edged pliers, screwdrivers, etc. Do not cut open fuel hoses with a knife or similar tool. Do not re-use fuel hoses after removal. Always install new hoses – fuel hoses may be overstretched during removal. Install new fuel hoses either dry or with the aid of STIHL press fluid, b 16. Other press fluids are not approved and may result in damage to the fuel hoses. Coat the ends of the hoses and the connectors with STIHL press fluid and then push the new hoses on to the hose barbs, b 16.

6 MS 780, MS 880 3. Specifications 3.1 Engine MS 780 MS 880 Displacement: 121.6 cm 3 121.6 cm 3 Bore: 60 mm 60 mm Stroke: 43 mm 43 mm Engine power to ISO 7293: 5.6 kW (7.8 bhp) at 8,000 rpm 6.4 kW (8.7 bhp) at 8,500 rpm Maximum permissible engine speed with bar and chain: 11,000 rpm 11,000 rpm Idle speed: 2,700 rpm 2,700 rpm Clutch: Centrifugal, without linings Centrifugal, without linings Clutch engages at: 3,400 rpm 3,400 rpm Crankcase leakage test at gauge pressure: 0.5 bar 0.5 bar under vacuum: 0.5 bar 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 in instruction manual 3.3 Ignition System Air gap between ignition module and fanwheel: 0.20...0.30 mm Spark plug (suppressed): NGK BPMR 7 A Electrode gap: 0.5 mm 3.4 Chain Lubrication Speed-controlled oil pump with reciprocating piston and manual flow control Oil delivery rate: Adjustable oil pump Ematic position at 10,000 rpm 14.0...36.0 (+/- 5.0) cm 3 /min 21.0 (+/- 3.0) cm 3 /min Special accessory Oil delivery rate: Oil pump with increased delivery rate: (oil delivery rate is not adjustable) at 10,000 rpm 50.0 (+/- 5.0) cm 3 /min

7 MS 780, MS 880 3.5 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 Nm Remarks Screw M 4x8 Chain tensioner cover plate/crankcase 3.5 Screw B 3.9x13 Cover plate/chain sprocket cover 2.0 Screw M 4x12 Exhaust cover/muffler 4.0 4) Screw M 4x12 Brake band/crankcase 3.0 1), 4) Screw M 6x30 Collar stud/crankcase, for muffler (MS 780/ new MS 880) 12.0 1) Screw M 10x27 Collar stud / crankcase, for bar 30.0 1) Screw M 4x12 Cover, chain brake/crankcase 3.5 4) Screw M 4x12 Cover, oil pump/crankcase 3.5 4) Screw M 4x12 Cover, spur gear/crankcase 3.0 4) M 10x1 Decompression valve 14.0 Nut M 5 Filter cover, twist lock 1.0 Nut M 5 Flange/carburetor/tank housing 5.0 Screw P 6x32.5 Handlebar, right, stiffener/tank housing 8.0 2) Screw P 6x21.5 Handlebar, bottom/tank housing 8.0 2) Screw M 5x35 Hand guard/fan housing/crankcase 7.0 4) Nut M 6 Helper's handle/front handle/screw (2-man saw) 6.0 Screw M 5x20 Shroud/crankcase 7.0 4) Nut M 5 Shroud/cylinder 3.5 Nut M 5 Chain catcher/spiked bumper/crankcase 6.0 Nut M 6 Spiked bumper/chain sprocket cover 7.5 Screw M 6x16 Spiked bumper/crankcase, top/locknut 7.5 4) Screw M 6x18 Spiked bumper/crankcase, top/locknut 7.5 4) Screw M 6x16 Spiked bumper/crankcase, bottom 7.5 1), 4 Screw M 6x18 Spiked bumper/crankcase, bottom (Z version) 7.5 1), 4) Screw M 5x25 Crankcase (old MS 880) 11.5 4) Screw M 5x28 Crankcase (MS 780/new MS 880) 10.0 4) Screw P 4x19 Bearing, switch shaft/tank housing 1.0 Screw M 5x20 Fan housing/crankcase 7.0 4) Carrier M 14x1 L Carrier / crankshaft 80.0 6) Screw M 4x12 Oil oump/crankcase, front top 3.5 4), 7) Screw M 4x12 Oil pump/crankcase, front bottom and rear 3.5 4)

8 MS 780, MS 880 Fastener Thread size For component Torque Nm Remarks Screw M 6x40 Annular buffer, left top/retainer/tank housing 7.0 1), 4) Screw P 6x19 Annular buffer, bottom/tank housing 5.5 Screw M 5x12 Annular buffer plate, left top/crankcase 9.0 1), 4) Screw M 4x12 Rewind spring, fan housing 4.0 4) Screw M 5 Muffler/collar stud with spring washer (MS 780/new MS 880) 10.0 Screw M 5x16 Muffler/cylinder (MS 780/new MS 880) 10.0 1), 4), 5) Screw M 5x6 Muffler casing, top (MS 780/new MS 880) 6.5 1), 4) Crankshaft M 10x1 Flywheel/crankshaft 45.0 6) Screw M 4x12 Segment/fan housing 2.0 4) Screw M 4x8 Side plate/crankcase 3.0 4) Screw M 3x20 Clamp/manifold (MS 780/new MS 880) 0.5 Stud M 5x8.5 Stud/cylinder 3.5 3) Screw M 5x16 Support/crankcase (old MS 880) 10.0 4) Screw M 5x16 Support/muffler (old MS 880) 10.0 4) Screw P 4x19 Tank housing/handle molding 1.0 Spark plug M 14x1.25 Spark plug 25.0 Screw M 5x25 Ignition module/crankcase (old MS 880) 9.0 1), 4) Screw M 5x20 Ignition module/crankcase 8.0 5) Screw M 6x30 Cylinder/crankcase 15.0 4) Remarks: 1) Loctite 242 or 243, medium strength 2) Loctite 649, high strength 3) Loctite 270, high strength 4) Screws with binding head 5) Micro-encapsulated screws 6) Degrease joint and mount oil-free 7) Use Hylomar HYL sealant 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. Coat micro-encapsulated screws with medium strength Loctite 242 or 243 before reinstalling. 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.

9 MS 780, MS 880 4. Troubleshooting 4.1 Clutch Condition Cause Remedy Saw chain stops under load at full throttle Clutch shoes badly worn Install new clutch Clutch drum badly worn Install new clutch drum Saw chain rotates at idle speed Engine idle speed too high Check carburetor settings and readjust properly if necessary Clutch springs stretched or fatigued Replace the clutch springs or install new clutch Clutch spring hooks broken Replace the clutch springs Loud noises Clutch springs stretched or fatigued Replace all clutch springs Needle cage damaged Fit new needle cage Clutch shoe retainer broken Install new retainer or clutch Clutch shoes and carrier worn Install new clutch

Stihl MS 880 Service Manual

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