Stihl MS 270 Power Tool Service Manual

STIHL MS 270, 280 2005-10 STIH)

1 MS 270, MS 280 q © 2002 Andreas Stihl AG & Co., Waiblingen Contents 1 Introduction 3 2 Safety Precautions 4 3 Specifications 5 3.1 Engine 5 3.2 Fuel System 5 3.3 Ignition System 5 3.4 Chain Lubrication 5 3.5 Tightening Torques 6 4 Troubleshooting Chart 8 4.1 Clutch, Chain Drive, Chain Brake, Chain Tensioner 8 4.2 Rewind Starter 10 4.3 Chain Lubrication 11 4.4 Ignition System 12 4.5 Carburetor 13 4.6 Engine 16 5 Clutch, Chain Drive, Chain Brake and Chain Tensioner 17 5.1 Clutch Drum/Chain Sprocket 17 5.2 Replacing the Chain Catcher 18 5.3 Clutch 18 5.4 Chain Brake 20 5.4.1 Checking Operation 20 5.4.2 Removing 21 5.4.3 Installing 23 5.5 Chain Brake with QuickStop Super 25 5.5.1 Removing 25 5.5.2 Installing 26 5.5.3 Checking Play 28 5.5.4 Adjusting Play 29 5.5.5 Brake Cable 29 5.5.6 Checking Operation of Coasting Brake 30 5.6 Brake Spring Anchor Pin 30 5.7 Chain Tensioner 31 5.8 Bar Mounting Studs 32 6 Engine 33 6.1 Muffler/Spark Arresting Screen 33 6.2 Leakage Test 33 6.2.1 Preparations 33 6.2.2 Pressure Test 34 6.2.3 Vacuum Test 35 6.3 Oil Seals 36 6.4 Shroud 37 6.5 Cylinder and Piston 38 6.5.1 Removing 38 6.5.2 Installing 39 6.6 Piston Rings 42 6.7 Crankcase 43 6.7.1 Crankshaft 43 6.8 Decompression Valve 44 7 Ignition System 44 7.1 Ignition Module 45 7.1.1 Ignition Timing 45 7.1.2 Removing and Installing 45 7.1.3 Testing the Ignition Coil 46 7.2 Spark Plug Boot 48 7.3 Flywheel 48 7.4 Short Circuit Wire/ Ground Wire 49 7.5 Stop Contact 50 7.6 Ignition System Troubleshooting 51 8 Rewind Starter 54 8.1 General 54 8.2 Fan Cover 54 8.3 Pawls 54 8.4 Rope Rotor 55 8.5 Starter Rope 56 8.5.1 ElastoStart 57 8.5.2 Tensioning 57 8.6 Starter Rope Guide Bush 58 8.7 Replacing the Rewind Spring 59 9 AV Handle System 60 9.1 Handlebar 60 9.2 Replacing Annular Buffers 61 9.2.1 Crankcase 61 9.2.2 Tank Housing 62 9.3 Spring 63 10 Master Control/ Handle System 64 10.1 Switch Shaft 64 10.2 Throttle Trigger/ Interlock Lever 65 10.2.1 Machines without QuickStop Super 65 10.2.2 Machines with QuickStop Super 66 11 Chain Lubrication 67 11.1 Pickup Body/ Suction Hose 67 11.2 Delivery Hose 68 11.3 Valve 69 11.4 Oil Pump 70 11.5 Fan Housing 70 12 Fuel System 71 12.1 Air Filter 71 12.2 Carburetor 72 12.2.1 Removing and Installing 72 12.2.2 Leakage Test 73 12.3 Servicing the Carburetor 73 12.3.1 Metering Diaphragm 73 12.3.2 Inlet Needle 74 12.3.3 Fixed Jet 75 12.3.4 Pump Diaphragm 76 12.3.5 Accelerator Pump 77 12.4 Adjusting 79 12.4.1 Standard Setting 80 12.5 Tank Vent 81 12.6 Pickup Body 82 12.7 Fuel Hose 82

2 MS 270, MS 280 Contents 13 Special Servicing Tools 83 14 Servicing Aids 84

3 MS 270, MS 280 1 Introduction This service manual contains detailed descriptions of all the typical repair and servicing procedures for 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 an updated edition is issued. The special tools mentioned in the descriptions are listed in chapter "Special Servicing Tools" 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. 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: Pointer Direction of movement Service manuals and all technical Information bulletins are intended exclusively for the use of STIHL servicing dealers. They must not be passed to third parties. Servicing and repairs are made considerably easier if the clamp (1) 5910 890 2000 is used to mount the machine on assembly stand (2) 5910 890 3100 so that one clamp screw engages the outer 10 mm bore (3) in the assembly stand. The chainsaw can then be swivelled to the best position for the ongoing repair. To service the underside of the machine, turn it upside down and mount it in the assembly stand. Pull the hand guard back against the front handle for this purpose. Always use original STIHL replacement parts. They can be identified by the STIHL part number, the STIH) STIH) STIH) STIH) logo and the STIHL parts symbol ( This symbol may appear alone on small parts.

4 MS 270, MS 280 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 owner’s manual. Gasoline is an extremely flammable fuel and can be explosive in certain conditions. Improper handling may result in burns or other serious injuries. Warning! 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. 2 Safety Precautions

5 MS 270, MS 280 3 Specifications 3.1 Engine MS 270 MS 280 Displacement: 49.6 cm 3 54.2 cm 3 Bore: 44.0 mm 46.0 mm Stroke: 32.6 mm 32.6 mm Engine power to ISO 7293: 2.6 kW (3.54 HP) at 9,500 rpm 2.8 kW (3.81 HP) at 9,500 rpm Max. permissible engine speed (with bar and chain): 13,500 ± 150 rpm 13,500 ± 150 rpm Idle speed: 2,800 rpm 2,800 rpm Clutch: Three-shoe centrifugal clutch without linings Three-shoe centrifugal clutch without linings Clutch engages at: 3,300 rpm 3,300 rpm Crankcase leakage test – at gauge pressure: – under vacuum: 60 kPa (0.6 bar) 40 kPa (0.4 bar) 60 kPa (0.6 bar) 40 kPa (0.4 bar) 3.2 Fuel System Carburetor leakage test at gauge pressure: 80 kPa (0.8 bar) 80 kPa (0.8 bar) Tank vent operates at gauge pressure: 30 kPa (0.3 bar) 30 kPa (0.3 bar) Fuel: see owner’s manual see owner’s manual 3.3 Ignition System Air gap between ignition module and fanwheel: 0.20 – 0.30 mm 0.20 – 0.30 mm Spark plug (resistor type): NGK BPMR 7A NGK BPMR 7A Electrode gap: 0.5 mm 0.5 mm 3.4 Chain Lubrication Fully automatic speed-controlled oil pump with rotary piston Oil delivery rate: 10 cc/min at 10,000 rpm 10 cc/min at 10,000 rpm

6 MS 270, MS 280 3.5 Tightening Torques DG and P screws (Plastoform) are used in polymer and light-alloy 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 always use a torque wrench. Fastener Thread For component Torque Remarks size Nm Spline screw IS-M4x8 Cover plate, chain tensioner/crankcase 3.0 1) Countersunk screw IS-PT4x12 Cover plate/chain sprocket cover 2.5 2) Spline screw IS-B3.9x13 Cover plate/fan cover 1.5 Spline screw IS-M8x22 Brake band/crankcase 10.0 3) Spline screw IS-P4x10 Brake cable, support/tank housing 1.0 4) Collar screw IS-M10/M8 Guide bar/crankcase 30.0 2) 5) 6) Collar screw IS-M8x21.5 Guide bar/crankcase 23.0 7) 3) 8) Spline screw IS-DG4x16 Cover/crankcase 3.0 Decompression valve IS-M10x1 Decompression valvel 14.0 Collar nut M5 Filter base/baffle/carburetor 5.0 Spline screw IS-B4.2x9.5 Screen/muffler 2.0 9) Spline screw IS-DG5x24 Hand guard, sleeve/fan cover 4.0 Spline screw IS-DG5x24 Shroud/crankcase 4.5 Spline screw IS-DG5x24 Shroud/fan housing 4.5 Spline screw IS-DG5x18 Chain catcher/crankcase 9.0 Spline screw IS-DG5x18 Spiked bumper/crankcase 9.0 Spline screw IS-DG5x24 Fan cover/fan housing 4.0 Remarks: 1) Special accessory 2) Only machines with quick chain adjuster 3) Secure screw with Loctite 243 4) Only machines with QuickStop Super 5) Secure screw with Loctite 270 6) With quick chain adjuster 7) Only machines without quick chain adjuster 8) Without quick chain adjuster 9) Only muffler with spark arresting screen

7 MS 270, MS 280 Fastener Thread For component Torque Remarks size Nm Spline screw IS-DG5x24 Fan housing/crankcase 9.0 Spline screw IS-DG5x24 Fan housing/bearing plug 4.0 Clutch carrier M12x1L Carrier/crankshaft 50.0 Spline screw IS-DG5x18 Muffler/cylinder 9.0 Nut M8x1 Flywheel/crankshaft 28.0 Pan head screw M4x8 Inner side plate 3.0 1) Collar screw M8SK6 Dihedral sleeve/crankcase/bar guide 30.0 1) 6) Spline screw IS-M5x28 Cylinder/crankcase 9.0 Spark plug M14x1.25 Spark plug 25.0 Spline screw IS-DG4x20 Ignition module/cylinder 4.0 Spline screw IS-DG4x16 Oil pump/crankcase 3.0 Remarks: 1) Only machines with quick chain adjuster 6) Secure screw with Loctite 270 Screws secured with adhesive are easier to loosen if the adhesive is heated first with a hot air blower. Exercise caution on polymer components. Use the following procedure to fit a P (Plastoform) screw in an existing thread: – Place the P screw in the hole and rotate it counterclockwise until 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, which would weaken the assembly. Power screwdriver speed setting for polymer: – P screws: max. 500 rpm

8 MS 270, MS 280 4 Troubleshooting Chart 4.1 Clutch, Chain Drive, Chain Brake, Chain Tensioner Condition Cause Remedy Saw chain stops under load at full throttle Clutch shoes badly worn Replace clutch shoes or install new clutch Clutch drum badly worn Install new clutch drum Brake band stuck Check freedom of movement and function of brake band. If necessary, adjust brake cable of QuickStop Super (option) QuickStop Super brake cable broken (option) Replace the brake cable Saw chain rotates at idle speed Engine idle speed too high Readjust with idle speed screw (counterclockwise) Clutch springs stretched or fatigued Replace the clutch springs 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 Chain sprocket wears rapidly Chain not properly tensioned Tension chain as specified Wrong chain pitch Fit chain of correct pitch

9 MS 270, MS 280 Condition Cause Remedy Saw chain does not stop immediately when brake is activated Brake spring stretched or broken Fit new brake spring Brake band stretched/worn/broken Fit new brake band

Stihl MS 270 Power Tool Service Manual

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