Stihl MS 240 MS 260 MS 250 MS 250 C Brushcutters & Parts Workshop Service Repair Manual

STIH) STIHL MS 240, 260 2008-07

1 MS 240, MS 260, MS 260 C q © ANDREAS STIHL AG & Co. KG, 2008 RA_165_00_01_03 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. Cutting Attachment 19 5.1 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 Side Chain Tensioner 28 7.6.1 Front Chain Tensioner 29 7.6.2 Quick Chain Tensioner 29 7.7 Bar Mounting Studs 30 8. Engine 31 8.1 Muffler / Spark Arresting Screen 31 8.2 Leakage Test 32 8.2.1 Preparations 33 8.2.2 Vacuum Test 34 8.2.3 Pressure Test 34 8.3 Oil Seals 35 8.4 Removing and Installing the Shroud 36 8.5 Cylinder 37 8.6 Crankshaft 40 8.6.1 Removing and Installing 40 8.6.2 Bearings / Crankcase 45 8.7 Piston 47 8.7.1 Removal 47 8.7.2 Installing 48 8.8 Piston Rings 49 8.9 Decompression Valve 50 9. Ignition System 51 9.1 Ignition Timing 51 9.2 Ignition Module 51 9.2.1 Removing and Installing 51 9.3 Testing the Ignition Module 54 9.4 Spark Plug Boot / Ignition Lead 55 9.5 Flywheel 56 9.6 Short Circuit Wire 57 9.6.1 Testing 57 9.6.2 Removing and Installing 57 9.6.3 Ground Wire 60 9.7 Ignition System Troubleshooting 61 10. Rewind Starter 64 10.1 General 64 10.2 Removing and Installing 64 10.3 Pawl 64 10.4 Rope Rotor 65 10.5 Starter Rope / Grip 66 10.6 Tensioning the Rewind Spring 67 10.7 Replacing the Rewind Spring 68 11. Servicing the AV System 70 11.1 Annular Buffer on Chain Catcher 70 11.2 Annular Buffer at Clutch Side 70 11.3 Annular Buffer at Ignition Side 71 11.4 Stop Buffer 72 11.5 Handlebar 72 11.6 Handlebar with Handle Heating 73 12. Control Levers 76 12.1 Switch Shaft 76 12.1.1 Removing and Installing 76 12.2 Throttle Trigger/Interlock Lever 77 13. Chain Lubrication 80 13.1 Pickup Body 80 13.2 Oil Suction Hose 80 13.3 Oil Delivery Hose 81 13.4 Non-Adjustable Oil Pump 81 13.5 Adjustable Oil Pump 82 13.6 Valve 83 14. Fuel System 85 14.1 Air Filter 85 14.2 Removing and Installing the Carburetor 85 14.3 Leakage Test 86 14.4 Servicing the Carburetor 87 14.4.1 Inlet Needle 89 14.4.2 Fixed Jet 89 14.4.3 Pump Diaphragm 90 14.4.4 Choke Shaft / Choke Shutter 91 14.4.5 Adjusting Screws 91 14.5 Adjusting the Carburetor 92 14.5.1 Basic Setting 92 14.5.2 Standard Setting 93 Contents

2 MS 240, MS 260, MS 260 C Contents 14.6 Throttle Rod 94 14.6.1 Removing and Installing the Intake Manifold 94 14.6.2 Impulse Hose 96 14.7 Tank Vent 96 14.7.1 Testing 96 14.7.2 Removing and Installing 97 14.8 Fuel Intake 98 14.8.1 Pickup Body 98 14.8.2 Fuel Suction Hose 98 14.8.3 Removing and Installing the Tank Housing 99 15. Heating System 100 15.1 Carburetor Heating 100 15.1.1 Testing the Complete System 100 15.1.2 Testing the Heating Element 100 15.1.3 Thermostatic Switch 101 15.2 Carburetor Heating System Troubleshooting Chart 103 15.3 Handle Heating System 104 15.3.1 Troubleshooting 104 15.4 Removing and Installing the Heater Switch 104 15.4.1 Heater Switch Ground Wire 105 15.5 Removing and Installing Heating Element in Rear Handle 106 15.6 Removing and Installing the Heating Element in the Handlebar 108 15.7 Removing and Installing the Generator 108 15.7.1 Handle Heating and Generator Trouble- shooting Chart 110 15.7.2 Test Connections and Test Values 112 15.8 Wiring Harness 114 16. Special Servicing Tools 116 17. Servicing Aids 118

3 MS 240, MS 260, MS 260 C 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 @ 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 240, MS 260, MS 260 C Engage the bar mounting studs in the outer bores in the mounting plate and secure the saw in position with the nuts (arrows). The chain sprocket cover and cutting attachment have to be removed before mounting the saw to the assembly stand – pull the hand guard toward the handlebar. 165RA000 TG Versions with Quick Chain Tensioner There is only one bar stud on these versions. It is pushed through the upper hole (arrow) in the mounting plate and secured with the nut (1). The machine is held in position on the mounting plate by the screw heads on the crankcase. 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. 165RA468 TG 1

5 MS 240, MS 260, MS 260 C 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.

6 MS 240, MS 260, MS 260 C 3. Specifications 3.1 Engine MS 240 MS 260, MS 260 C Displacement: 41.6 cm 3 50.2 cm 3 Bore: 42 mm 44.7 mm Stroke: 30 mm 32 mm Engine power to ISO 7293: 2.1 kW (2.85 bhp) at 9500 rpm 2.6 kW (3.5 bhp) at 9500 rpm Maximum permissible engine speed (with bar and chain): 13000 rpm 14000 rpm Versions with catalytic converter Maximum permissible engine speed (with bar and chain): 13000 rpm Idle speed: 2800 rpm 2800 rpm Clutch: Centrifugal clutch without linings Centrifugal clutch without linings Clutch engages at: 3600 rpm 3600 rpm Crankcase leakage test at gauge pressure: 0.5 bar under vacuum: 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 BPMR 7 A Electrode gap: 0.5 mm 3.4 Chain Lubrication Speed-controlled oil pump with reciprocating piston and manual flow control Oil pump without adjustable delivery rate: 7.5 (+/- 2.5) cm 3 /min at 10000 rpm Oil pump with adjustable delivery rate: 4.5...11.5 cm 3 /min at 10000 rpm

7 MS 240, MS 260, MS 260 C 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 Letter Countersunk screw P 4x12 Cover plate/sprocket cover (quick chain tensioner) 2.5 Screw M 4x8 Cover plate/chain tensioner 3.0 4) Collar screw M 8x21.5 Bar mounting 23.0 1) Collar screw M10/M 8 Bar mounting/quick chain tensioner 30.0 1) Screw M 4x12 Cover, chain brake/crankcase 3.0 4) M 10x1 Decompression valve (MS 260) 14.0 Screw B 4.9x9.5 Spark arresting screen/muffler 2.0 Screw M 3.5x12 Generator/crankcase 2.0 1) Screw P 6x32.5 Handlebar, top (polymer)/tank housing 5.0 Screw P 6x21.5 Handlebar, bottom (polymer)/tank housing 5.0 Screw P 6x19 Handlebar, top and bottom/tank housing (version with handle heating) 7.0 Screw P 4x19 Handle molding 1.6 Screw M 5x12 Retaining plate/annular buffer 8.0 4) Screw M 4x16 Hand guard/crankcase (micro-encapsulated) 4.0 4) Nut M 5 Slotted nut, shroud/stud, cylinder 3.5 Screw P 6x19 Chain catcher/plug 2.8 Screw M 5x12 Spiked bumper (with self-locking nut) 7.5 4) Screw M 5x20 Crankcase 9.0 Collar nut M 5 Air filter/tank housing 2.0 Screw M 4x16 Fan housing 4.0 4) M 12x1L Carrier (clutch) 50.0 Screw M 4x12 Oil pump/crankcase 3.0 4) Screw P 6x26.5 Annular buffer, tank housing/crankcase (ignition side) 5.0 Screw M 5x12 Annular buffer plate/crankcase (ignition side) 8.0 4) Screw P 6x19 Annular buffer, tank housing/crankcase (clutch side) 5.5 Screw M 5x16 Muffler/crankcase/cylinder (version with catalytic converter and MS 260) 10.0 1), 4)

8 MS 240, MS 260, MS 260 C Fastener Thread size For component Torque Nm Remarks Screw M 5x12 Muffler/crankcase/cylinder (MS 240) 10.0 1), 4) Nut M 8x1 Flywheel 33.0 3) Screw M 4x8 Side plate/crankcase 3.0 4) Screw M 4x16 Side plate/crankcase (quick chain tensioner) 3.0 Screw M 3x20 Clamp/manifold 0.5 M 5x8.5 Stud/cylinder 1.4 2) Nut M 5 Carburetor 3.5 Screw M 5x20 Cylinder/crankcase 11.0 2), 4) M 14x1.25 Spark plug 25.0 Screw M 5x20 Ignition module/crankcase (micro- encapsulated) 7.0 4) Remarks: 1) Loctite 242 or 243, medium strength 2) Loctite 270, high strength 3) Degrease crankshaft/flywheel and mount oil-free 4) Screws with binding head 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 240, MS 260, MS 260 C 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 Readjust with idle speed screw LA (counterclockwise) 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 Fit new retainer Clutch shoes and carrier worn Install new clutch

Stihl MS 240 MS 260 MS 250 MS 250 C Brushcutters & Parts Workshop Service Repair Manual

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