STIHL 4180 Powerhead Service & Repair Manual

Online version - not for reprint 1 Series 4180 Powerhead © 2002 Andreas Stihl AG & Co., Waiblingen Contents 1 Introduction 2 2 Safety Precautions 3 3 Specifications 4 3.1 Engine 4 3.2 Spark Plug 4 3.3 Carburetor 4 3.4 Tightening Torques 5 4 Troubleshooting 6 4.1 Clutch 6 4.2 Rewind Starter 7 4.3 Ignition System 8 4.4 Carburetor 9 4.5 Engine 11 5 Rewind Starter / Shroud 13 5.1 General 13 5.2 Removing and Installing 13 5.3 Rope Rotor 13 5.4 Starter Rope 15 5.4.1 Tensioning 16 5.5 Pawl 17 5.6 Replacing the Rewind Spring 17 5.7 Removing the Shroud 17 6 Fuel System 18 6.1 Air Filter 18 6.2 Carburetor 18 6.2.1 Leakage Test 18 6.2.2 Removing and Installing 19 6.3 Servicing the Carburetor 20 6.3.1 Manual Fuel Pump 20 6.3.2 Metering Diaphragm 21 6.3.3 Inlet Needle 21 6.3.4 Fixed Jet 22 6.3.5 Pump Diaphragm 22 6.3.6 Adjusting Idle Speed 23 6.3.7 Factory Setting 24 6.4 Tank Vent 25 6.5 Pickup Body 25 6.6 Fuel Hoses 26 6.7 Fuel Tank 26 7 Engine 27 7.1 Compression Pressure 27 7.2 Checking / Adjusting Valve Clearances 27 7.3 Rocker Arms / Pushrods 29 7.4 Cam Followers 30 7.5 Cam Gear 30 7.5.1 Decompression System 31 7.6 Muffler / Spark Arresting Screen 31 7.7 Clutch 32 7.7.1 Removing and Disassembling 32 7.7.2 Assembling and Installing 33 7.7.3 Clutch Drum 34 7.7.4 Clutch Drum Bearing 35 7.8 Flywheel 35 7.9 Crankshaft 36 7.9.1 Replacing the Oil Seals 36 7.9.2 Crankcase, Lower Half 38 7.9.3 Crankshaft 39 7.9.4 Piston 40 7.9.5 Piston Rings 42 7.10 Valves / Valve Springs 42 7.11 Upper Half of Crankcase with Cylinder 43 8 Ignition System 44 8.1 Spark Plug Boot 44 8.2 Ignition Module 45 8.2.1 Ignition Timing 45 8.2.2 Removing and Installing 45 9 Throttle Control 46 9.1 Throttle Trigger, Interlock Lever 46 9.2 Tensioner 48 9.3 Adjusting Throttle Cable 48 9.4 Slide Control 48 10 AV System 49 11 Special Accessories 50 12 Special Servicing Tools 51

Online version - not for reprint 2 Series 4180 Powerhead This service manual contains detailed descriptions of all repair and servicing procedures specific to this powerhead. 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 or any replacement parts. 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 servicing tools mentioned in the descriptions are listed in the last chapter of this manual. Use the part numbers to identify the tools in the "STIHL Special Tools" manual. 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 machine is mounted on assembly stand (2) 5910 890 3100 with the aid of clamp (1) 5910 890 8800. The powerhead can then be swivelled to the best position for the ongoing repair. This leaves both VA 249RA!63 2 1 hands free. Always use original STIHL replacement parts. They can be identified by the STIHL part number, the 67,+logo and the STIHL parts symbol This symbol may appear alone on small parts. 1 Introduction

Online version - not for reprint 3 Series 4180 Powerhead 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

Online version - not for reprint 4 Series 4180 Powerhead 3 Specifications 3.1 Engine STIHL single cylinder four-stroke engine with gasoil mixture lubrication Displacement: 31.4 cm 3 Bore: 40 mm Stroke: 25 mm Engine power to ISO 8893 at 7,000 rpm: 1.0 kW Max. permissible engine speed without cutting attachment – with cut-off in ignition module: 10,500 ± 500 rpm Bearings: Crankshaft supported in heavy-duty ball bearings, needle cages on small and big ends, plain bearings on piston pin Piston pin diameter: 8 mm Clutch: Centrifugal clutch, two clutch shoes without linings Clutch engages at: 3,700 rpm 3.2 Spark Plug Type NGK CMR 6H Electrode gap: 0.7 mm 3.3 Carburetor Standard setting Low speed adjusting screw: Open one full turn High speed adjusting screw: Open two full turns Idle speed: 2,800 rpm Max. engine speed: 10,500 ± 500 rpm

Online version - not for reprint 5 Series 4180 Powerhead 3.4 Tightening Torques DG screws are used in polymer and lightmetal 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 Spline screw IS-M6x25 Cover washer/Clutch shoe/Flywheel 12 Spline screw IS-D4x18 Cover/Engine pan 4.5 Spline screw IS-D4x18 Cover/Cylinder 4.5 Spline screw IS-M5x21 Filter cover/Filter housing 3.5 Collar nut M8 Filter housing/Carburetor 3.5 Spline screw IS-M5x24 Shroud/Cylinder 6 Collar screw M5x16 Rocker lever collar screw/Cylinder 9 Spline screw IS-DG5x24 Engine pan/Cylinder 9 Spline screw IS-M5x24 Fan housing/Shroud/Engine pan 6 Spline screw IS-M5x24 Fan housing/Engine pan 6 Spline screw IS-DG5x24 Muffler/Cylinder 9 Nut M8x1 Flywheel/Crankshaft 17 Spline screw IS-DG5x24 Starter cover/Cover/Engine pan 6 Spline screw IS-DG5x24 Starter cover/Tank/Engine pan 6 Nut M8x1 Starter cup/Crankshaft 17 Spline screw IS-M5x30 Valve cover/Cylinder 3.5 Spline screw IS-D5x32 Spacer flange/Cylinder 9 Spark plug IS-M10x1 Spark plug 9 Spline screw IS-D4x18 Ignition module/Cylinder 4.5 Use the following procedure when refitting a DG 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. Note: Power screwdriver settings for polymer: DG screws max. 500 rpm

Online version - not for reprint 6 Series 4180 Powerhead 4 Troubleshooting 4.1 Clutch Condition Cause Remedy Tool stops at full throttle under load Clutch badly worn Fit new clutch Clutch drum badly worn Fit new clutch drum Tool runs at idle speed Idle speed too high Readjust idle speed screw (counterclockwise) Clutch springs stretched or fatigued Fit new clutch Spring hooks broken Fit new clutch

Online version - not for reprint 7 Series 4180 Powerhead 4.2 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 Rewind spring broken (starter rope does not rewind) Spring overtensioned – no reserve when rope is fully extended Fit new rewind spring Very dirty or corroded Clean rewind spring or fit a new one 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 Spring clip fatigued Fit new spring clip Starter rope is difficult to pull and rewinds very slowly Starter mechanism very dirty (dusty conditions) Thoroughly clean complete starter mechanism Lubricating oil on rewind spring becomes viscous at very low outside temperatures (spring windings stick together) Apply a few drops of kerosine (paraffin) to spring, then pull rope carefully several times until normal action is restored. Then coat with resin-free oil.

Online version - not for reprint 8 Series 4180 Powerhead 4.3 Ignition System Warning: Exercise extreme caution while carrying out maintenance and repair work on the ignition system. The high voltages which occur can cause serious or fatal injuries! Condition Cause Remedy Engine runs roughly, misfires, temporary low of power Spark plug boot is loose Press boot firmly onto spark plug, and fit a new leg spring if necessary Spark covered in soot, smeared with oil Install new spark plug Weak spark or no spark Faulty insulation on ignition lead or short circuit wire. Use ohmmeter to check ignition lead for break. If break is detected or resistance is high, fit new ignition lead. Wrong air gap between ignition coil and flywheel Reset air gap Flywheel cracked or damaged Install new flywheel Crankcase damaged (cracks) Install new crankcase Check operation of spark plug. Check slide control, ignition coil/ wire for damaged insulation and leakage current Replace or clean spark plug, replace damaged parts of ignition system No spark Check operation of slide control and ignition coil

Online version - not for reprint 9 Series 4180 Powerhead 4.4 Carburetor Condition Cause Remedy Carburetor floods, engine stalls Inlet needle not sealing. Foreign matter in valve seat or cone damaged Remove and clean or replace inlet needle, clean fuel tank, pickup body and fuel line if necessary Inlet control lever sticking on spindle Free off inlet control lever Helical spring not located on nipple of inlet control lever Remove inlet control lever and refit correctly Perforated disc on diamphragm is deformed and presses constantly against inlet control lever Fit new metering diaphragm Inlet control lever too high (relative to design position) Set inlet control lever flush with upper face of housing or bottom of metering chamber After five starting attempts with choke shutter closed Open choke shutter after no more than five starting attempts Poor acceleration Idle jet too lean Back off low speed screw slightly Main jet too lean Back off high speed screw slightly Inlet control lever too low (relative to design position) Set inlet control lever flush with upper face of housing or bottom of metering chamber Inlet needle sticking to valve seat Remove inlet needle and clean valve seat Connecting bore to atmosphere blocked Clean bore Diaphragm gasket leaking Fit new diaphragm gasket Metering diaphragm damaged or shrunk Fit new metering diaphragm

Online version - not for reprint 10 Series 4180 Powerhead Condition Cause Remedy Engine will not idle, idle speed too high Throttle shutter opened too wide by idle speed screw Reset idle speed screw (LA) Intake stub leaking Seal or replace intake stub Engine stalls at idle speed Idle jet bores or ports blocked Clean jet bores and ports and blow clear with compressed air Idle jet too rich Screw dow low speed screw (L) slightly Setting of idle speed screw incorrect – throttle shutter completely closed Set idle speed screw (LA) correctly Engine speed drops quickly under load – low power Air filter plugged Clean air filter Tank vent faulty Clean or replace tank vent if necessary Leak in fuel line between tank and fuel pump Seal or renew connections and fuel line Pump diaphragm damaged or fatigued Fit new pump diaphragm Main jet bores or ports blocked Clean bores and ports Fuel pickup body dirty Fit new pickup body Fuel strainers dirty Clean fuel strainers

STIHL 4180 Powerhead Service & Repair Manual

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