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STIHL Series 4180 Powerhead

1. Turn engine over several times and then check valve clearance again Assemble all parts in the reverse sequence Thoroughly clean the sealing faces on the cylinder and cover Apply thin coating of sealant to cylinder sealing face Follow maker s instructions Tighten down cam gear cover screws in crosswise pattern 3 4 Install new gasket for valve cover Use new sealing ring for spline socket head screw Tighten down valve cover screw firmly 3 4 Tighten down nut on starter cup m 3 4 Tighten down spark plug 3 4 34 7 3 Rocker Arms Pushrods 249RA053 VA Remove the valve cover and cam gear cover L 7 2 Set piston to T D C 7 2 Remove the locknut 1 249RA054 VA Remove the sleeve 1 249RA055 VA Remove the rocker arm Take out the pushrod 1 Reassemble in the reverse sequence Make sure that the pushrod is firmly seated in the rocker arm and cam follower Adjust valves 7 2 Series 4180 Powerhead 7 4 Cam Followers Cam Gear N ANY 249RA057 VA Remove the pushrods 7 3 Pull out the pin 1 Remove the cam followers 2 a A Pull out the pin 1 Remove the cam gear 2 Inspect the removed parts and replace as necessary Install in the reverse sequence Check the length
2. Remove the sleeve and slip it onto the other end of the shank Inner pin must point towards flat face 249RA149 VA Apply the installing tool to the piston boss hold the piston steady center the tool shank exactly and press home until the snap ring slips into the groove Series 4180 Powerhead Fit the snap ring so that its gap is on the piston s vertical axis it must point either up or down Install the crankshaft 7 8 3 7 8 5 Piston Rings Remove rings from piston 249RA090 VA Use a piece of old piston ring to scrape the grooves clean Install new piston rings Check that piston ring gaps are offset 120 degrees Install the piston 7 8 4 47 7 9 Valves Valve Springs Valves are distinguished by the mark 1 on the valve head and the head diameter d Valves marked AM and BK or o may be used for the inlet side only If used valves are reinstalled take care not to mix up the inlet and exhaust valves Only valves marked E or I are available as replacements These valves may be installed at either the inlet or exhaust side also in older engines Assignment of valves to machines 3 1 Remove the valves as follows Remove rocker arms pushrods 17 3 Remove the crankshaft 7 8 3 48 Press valve spring retainer 1 down and move it sideways so that the valve stem is in the large
3. D o S z ira 5 Use the assembly drift 2 1110 893 4700 to push the piston pin 1 out of the piston If the piston pin is stuck tap the end of the drift lightly with a hammer if necessary Hold the piston steady to ensure that no jolts are transmitted to the connecting rod lt x o 3 q oc D A Inspect piston rings and replace if necessary 7 8 5 Reassemble in the reverse sequence 45 249RA091 VA 249RA144 VA Indentation arrow in piston crown faces the spark plug hole Use the assembly drift 1114 893 4700 to push the piston pin through the piston and connecting rod 46 Use installing tool 5910 890 2206 to fit the snap ring 11 If installing tool 5910 890 2208 is available it can equipped with a new sleeve 5910 893 1703 and used for this operation Remove sleeve from the tool lt gt its st lt oc a A Attach the snap ring 1 to the magnet 2 so that the snap ring gap is on the flat side of the tool s shank Push the large slotted diameter of the sleeve over the magnet and snap ring Position the sleeve so that the inner pin 1 points towards the flat face 2 of the tool s shank 249RA147 VA Stand the installing tool sleeve downward on a flat surface wooden board and press vertically downwards until the sleeve butts against the tool s shoulder Series 4180 Powerhead ae 249RA148 VA
4. Reassemble in the reverse sequence 22 6 2 4 Metering Diaphragm 249RA112 VA Remove the flange 6 2 3 Remove metering diaphragm 1 and gasket 2 from the carburetor body If the gasket and diaphragm are stuck together separate them carefully Check the diaphragm and gasket and replace if necessary The diaphragm is the most delicate part of the carburetor It is subjected to continuous alternating stresses and the material eventually shows signs of fatigue i e the diaphragm distorts and swells and has to be replaced Reassemble in the reverse sequence lt gt o T 5 Place the gasket 1 on the carburetor body The cutout in the gasket 2 must line up with the compensating bore in the carburetor 249RA114 VA Place the metering diaphragm 1 on the gasket The cutout in the metering diaphragm 2 must line up with the compensating bore in the carburetor and the gasket Assemble all other parts 6 2 3 Series 4180 Powerhead 6 2 5 Inlet Needle 249RA126 VA 6 2 6 Fixed Jet 249RA128 VA 6 2 7 Pump Diaphragm Remove the metering diaphragm 6 2 4 Remove the round head screw 1 Carefully remove the inlet control lever 1 with spindle Reassemble in the reverse sequence Engage clevis of inlet control lever in groove on inlet needle Helical spring must locate in inlet control lever s recess Make su
5. Remove handle molding 58 Remove the torsion spring Remove the trigger 1 with attached throttle cable 2 from the pivot 2 TON a gt o oO lt x oc Ss D A Disconnect throttle cable from the trigger 250RA130 VA 249RA104 VA Take the tensioner 1 out of the guide and remove the throttle cable 392RA085 VA Lift the interlock lever 1 a little and turn it to the side until the torsion spring 2 is relieved of tension Pull the interlock lever off the pivot Series 4180 Powerhead Remove the torsion spring Reassemble in the reverse sequence Make sure the throttle cable and protective tube are correctly positioned Tighten down the screws LQ 3 4 Open the throttle fully several times so that the slide automatically adjusts throttle cable tension Series 4180 Powerhead 9 2 Tensioner 249RA122 VA Remove the carburetor 6 2 2 Swing tensioner 1 vertically upwards and pull it off forwards Reassemble in the reverse sequence 9 3 Adjusting Throttle Cable 9 3 1 Control Handle with Slide Remove the shroud 5 7 Adjust idle speed screw correctly 249RA197 BL Screw the tensioning screw 1 into the tensioner 2 until equal lengths of thread arrows are visible above and below the tensioner 249RA198 BL Check that the slide on the control handle is
6. hole Remove the retainer 1 with valve spring 2 Take the valves out of the cylinder N 249RA204 BL Inspect seats on valve heads 1 and 2 and replace parts as necessary Inspect valve seats in cylinder head and valve heads for any damage Replace if necessary Valve spring retainer must engage properly in groove of valve stem Reassemble in the reverse sequence When installing check the valves again 3 1 Series 4180 Powerhead 7 10 Upper Half of Crankcase with Cylinder Remove the valves 7 9 Remove the cam gear 7 4 Remove the muffler 7 5 Remove the carburetor GJ 6 2 2 Remove gasket 1 from the cylinder head Reassemble in the reverse sequence Use a new gasket Take out the screws 1 and 2 Remove spacer flange 3 and tensioner for throttle cable 4 q gt fe A 3 lt x oc D A Take screws 1 and 2 out of the spacer flange Series 4180 Powerhead Tighten down the screws 1 and 2 013 4 Screw heads 1 and 2 must be completely recessed in the spacer flange after installation 7 11 Leakage Test Defective oil seals and gaskets or cracks in castings are the usual causes of leaks Such faults allow supplementary air to enter the engine and change the fuel air mixture This may upset the lubricating process or cause it to fail completely The engine can be
7. on the pawl and point it counterclockwise Handle the spring clip with care The rewind starter may not function properly if the spring clip is deformed Fit the starter rope 5 4 Tension the rewind spring 5 4 1 15 5 4 Starter Rope Remove the rewind starter 5 2 Remove the remaining rope from the rope rotor and starter grip Thread end of new rope through the underside of the starter grip and pull it out Secure the end of the rope with one of special knots shown Pull the rope back into the starter grip 16 249RA028 VA Thread the other end of the rope through the guide bush 2 from outside Thread the rope through the hole in the side of the rope rotor 1 Pull out the rope and secure it with a simple overhand knot 249RA029 VA Pull the rope back into the rotor so that the knot locates in the recess 1 Tension the rewind spring 5 4 1 Series 4180 Powerhead 5 4 1 Tensioning Remove the rewind starter 5 2 Make a loop in the starter rope lt x gt ite lt q a D Q Engage the rope in the notch on the rotor Grip the rope close to the rotor and use it to turn the rope rotor six full turns clockwise Series 4180 Powerhead 249RA155 VA Hold the rope rotor steady Pull out the rope with the starter grip and straighten it out Hold the starter grip firmly to keep the r
8. DG5x24 Starter cover tank engine pan 6 0 Nut M8x1 Starter cup crankshaft 17 0 Spline socket screw IS M5x30 Valve cover cylinder 3 5 Screw plug M11x10 Screw plug gearbox 10 0 Spark plug IS M10x1 Spark plug 9 0 Spline socket screw IS DG4x18 Ignition module cylinder 4 5 Spline socket screw IS DG5x32 Spacer flange cylinder 9 0 Spline socket screw IS P5x14 Ball bearing fan housing 4 0 Remarks 1 Version with bike handle 2 Version with loop handle 3 CombiEngine 4 FS 100 RX 5 FS 90 100 KM 90 100 FC 90 95 100 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 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 for polymer DG and P screws max 500 rpm Do not use an impact screwdriver for releasing or tightening screwed assemblies Do not mix up screws with and without binding heads Series 4180 Powerhead 4 Troubleshooting 4 1 Clutch Condition Cause Remedy Tool stops at full throttle under load Clutch badly worn Clutch drum badly worn Fit new clutch Fit new clutch drum Tool runs at idle speed Idle speed too high Clutch springs stretched or fatigued Spring hooks broken Readjust idle speed screw counterclo
9. E 12 3 2 Spark Plug Type BOSCH USR 7AC BOSCH USR 7AC NGK CMR 6H Electrode gap 0 5 mm 0 5 mm 0 7 mm Air gap between ignition module and fanwheel 0 15 0 30 mm 0 15 0 30 mm 0 15 0 30 mm 3 3 Fuel System Crankcase leakage test at gauge pressure 0 5 bar 0 5 bar 0 5 bar under vacuum 0 5 bar 0 5 bar 0 5 bar Carburetor leakage test at gauge pressure 0 8 bar 0 8 bar 0 8 bar Function of tank vent at gauge pressure 0 3 bar 0 3 bar 0 3 bar Fuel as specified in instruction manual Remarks 1 install at inlet side only may be installed at inlet and exhaust sides Series 4180 Powerhead 3 4 Tightening Torques DG and P screws Plastoform 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 Spline socket screw IS M6x25 Cover washer clutch shoe flywheel 12 0 Spline socket screw IS DG4x18 Cover engine pan 4 5 Spline socket screw 1S M5x30 Control handle locknut with washer 2 0 1 Spline socket screw IS P4x16 Control handle inner outer moldings 1 3 1 Spline socket screw IS P4x16 Control handle inner outer moldings 1 32 Spline socket screw IS M5x12 Clamp contro
10. as follows Pressure die cast fan housing Remove the retaining ring 1 Press out the ball bearing 2 in the direction of the engine a 3 S A Polymer fan housing Take out the screw 1 Use a suitable arbor to press the ball bearing 2 out of its seat All models Replace all damaged parts Reassemble in the reverse sequence Install new ball bearing with press arbor 4119 893 7200 Polymer fan housing Fit the screw 1 3 4 39 7 7 Flywheel Crankshaft 1 and flywheel 2 are an interference fit The crankshaft and flywheel are pressed together with such force that the flywheel cannot turn on the crankshaft For this reason the mating surfaces must be free from grease and oil The conical interference fit ensures the flywheel is exactly centered and runs smoothly with a minimum of runout The key 3 is used only to position the flywheel in relation to the crankshaft correct ignition timing Nut 4 pushes the flywheel 2 onto the crankshaft 1 to achieve the required interference fit 40 249RA071 VA Remove the clutch 7 6 1 Remove the hex nut 1 249RA072 VA Installing the flywheel Clean the stub of the crankshaft and the flywheel hub bore with a standard commercial solvent based degreasant containing no chlorinated or halogenated hydrocarbons EJ 12 Check Woodruff key or integrally cast
11. checked for leaks with the carburetor and crankcase tester 1106 850 2905 and the vacuum pump 0000 850 3501 Preparations Set the slide control to STOP Remove the shroud 5 7 Remove the filter cover and air filter 6 1 Remove the filter housing and gasket 6 1 Open the tank cap to release pressure and then close it again Disconnect the fuel hoses and impulse hose from the carburetor GJ 6 2 2 Disconnect the throttle cable 6 2 2 Remove the carburetor 6 2 2 49 oe A Le CC 249RA191 BL Push the test flange 1 1119 850 4201 into position Fit the sleeves 2 0000 963 1008 and secure them in position with the nuts 3 Seal the impulse hose 4 with a suitable plug 5 Loosen the muffler mounting screws a gt S a Fit the sealing plate 1 0000 855 8106 between the muffler and cylinder exhaust port the sealing plate must completely cover the opening in the muffler 50 Tighten down the screws firmly Vacuum test Oil seals tend to fail when subjected to a vacuum i e the sealing lip lifts away from the crankshaft during the piston s induction stroke because there is no internal counter pressure lt XN 249RA193 BL Connect suction hose 1 of vacuum pump 000 850 3501 to nipple 2 Close the vent screw on the pump Operate the pump until the pre
12. fuel tanks with a 5 2 mm shoulder a Check function of tank vent by carrying out pressure and vacuum tests on fuel tank via the fuel hoses Perform the following operations Pull both fuel hoses 1 and 2 off the carburetor Seal fuel hose 1 with a suitable plug 27 Vacuum test Connect hose 2 to vacuum pump 0000 850 3501 and test fuel tank under vacuum Equalization of pressure takes place via the tank vent There must be no build up of vacuum in the tank If the tank vent does not operate properly replace it together with the O ring 6 5 2 Pressure test Connect the carburetor and crankcase tester 1106 850 2905 to fuel hose 2 GQ 6 2 1 Pump air into the tank with the rubber bulb until the pressure gauge shows a reading of approx 0 5 bar If this pressure remains constant for at least 20 seconds the tank and tank vent are airtight If the pressure drops find the leak and replace either the tank 6 6 3 or the tank vent EQ 6 5 2 After completing the test disconnect the tester and reassemble all parts 28 6 5 2 Replacing Tank Vent Remove the faulty tank vent Pull both fuel hoses off the carburetor 6 5 1 Tank vent with return line Pull hose 1 of tank vent 2 off the filter housing 3 Both tank vent systems Carefully pry the tank vent out of the tank Do not reuse the old tank vent Fit a new O ring on t
13. high speed screw H 2 turns counterclockwise Open the low speed screw L 3 turns counterclockwise FS KM 130 C1Q S98 Open the high speed screw H 4 turns counterclockwise Open the low speed screw L 2 3 8 turns counterclockwise Series 4180 Powerhead 249RA166 VA All models Place the new limiter caps on the screws 1 and 2 so they are positioned against the rich stop arrow Push limiter caps onto the screws to the second noticeable stop until dimension a is 5 mm Limiter caps must not butt against the carburetor body Adjust engine idle speed 6 4 Series 4180 Powerhead 6 5 Tank Vent 6 5 1 Checking Operation Correct operation of the carburetor is only possible if atmospheric pressure and internal fuel tank pressure are equal at all times This is ensured by the tank vent In the event of trouble with the carburetor or the fuel supply system always check the tank vent There are two types of tank vents Tank vent A without return line Tank vent B with connection to return line on the clean air side of the air filter 249RA173 BL Only tank vent A without return line may be installed in fuel tanks with a 2 2 mm shoulder a 249RA174 BL A tank vent with return line B may be installed or retrofitted in
14. of idle speed screw incorrect throttle shutter completely closed Clean jet bores and ports and blow clear with compressed air Screw down low speed screw slightly Set idle speed screw LA correctly Engine speed drops quickly under load low power Air filter plugged Tank vent faulty Leak in fuel line between tank and fuel pump Pump diaphragm damaged or fatigued Main jet bores or ports blocked Fuel pickup body dirty Fuel strainers dirty Clean air filter Clean the tank vent replace if necessary Seal or renew connections and fuel line Fit new pump diaphragm Clean bores and ports Fit new pickup body Clean fuel strainers Series 4180 Powerhead 11 4 5 Engine Always check and if necessary repair the following parts before looking for faults on the engine Air filter Fuel system Carburetor Ignition system Condition Cause Remedy Engine does not start easily stalls at idle speed but operates normally at full throttle Check compression Gasket on carburetor spacer flange leaking Decompression lever sticking Muffler carbonized Crankcase damaged cracks Check combustion chamber for excessive build up of combustion deposits check condition of valves and valve clearances Install new gasket Install new cam gear Clean muffler or replace if necessary Replace the crankcase Engine does not deliver full power or runs erratically S
15. of sealant to outside diameter of oil seal 12 Slip the installing sleeve 4112 893 2400 1 over the end of the crankshaft q gt e 4 oc D A Push the oil seal 1 over the installing sleeve and up against the crankcase Note installed position Closed side of the oil seal 1 must face rewind starter 41 Press home the oil seal 1 with press sleeve 1115 893 4600 2 so that it is flush with the crankcase Remove the installing sleeve 2 and press sleeve 1 Fit the starter cup on the crankshaft Tighten down hex nut 3 4 Remove the locking screw 4180 890 2700 Fit spark plug and tighten down firmly EQ 3 4 Install the rewind starter 5 2 Install the shroud 5 7 Flywheel side Remove the rewind starter 5 2 Remove the shroud 5 7 Remove complete clutch 7 6 1 Remove the flywheel 7 7 42 Apply puller 4112 890 4400 1 with No 3 1 jaws 2 and clamp the arms Pull out the oil seal Take special care not to damage the crankshaft stub Installing oil seal at flywheel side Inspect crankshaft running face for scores Clean the sealing face in the crankcase and lubricate sealing lip of oil seal with grease 12 Slip installing sleeve 4112 893 2400 1 over the end of the crankshaft Lubricate sealing lips of oil seal with grease 12 App
16. 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 4 2 Reference to another chapter i e chapter 4 2 in this example I Situation applies from serial No Situation applies up to serial No In the illustrations P Pointer map Direction of movement Service manuals and technical information bulletins are intended exclusively for the use of properly equipped repair shops They must not be passed to third parties lt Pa 2 Lg lt x a D A Servicing and repairs are made considerably easier if the powerhead 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 hands free Always use original STIHL replacement parts They can be identified by the STIHL part number the S TZ L logo and the STIHL parts symbol amp 2 This symbol may appear alone of small parts Series 4180 Powerhead 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
17. 3 7200 Installing clutch drum bearing Series 4180 Powerhead 63 12 Special Accessories No Part Name Part No Application 1 Lubricating grease 225 g tube 0781 1201111 Oil seals 2 Press fluid OH 723 0781 957 9000 Rubber elements of AV system 50 ml and 100 ml bottle Fuel line connector Grommet on molded hose one part system 3 STIHL special lubricant 0781 417 1315 Bearing bore in rope rotor rewind spring in rope rotor 4 Dirko HT red sealant 0783 830 2000 Crankcase sealing faces 90 g tube 5 Electrician s repair kit 5910 007 1050 Electrical system 6 Set of screws 5910 007 1060 Screwed joints 7 Standard commercial solvent Cleaning crankshaft stub and based degreasant containing no flywheel taper chlorinated or halogenate hydrocarbons 64 Series 4180 Powerhead
18. 5910 890 2208 Snap ring on piston pin 9 with sleeve 5910 893 1703 10 Carburetor and crankcase tester 1106 850 2905 Testing crankcase and carburetor for leaks 11 Vacuum pump 0000 850 3501 Testing crankcase for leaks 12 Feeler gauge 4180 893 6400 Adjusting valve clearance 13 Puller 4119 890 4501 Removing fanwheel 14 Puller 5910 890 4400 Universal puller Jaws with No 2 profile Removing AV element Jaws with No 3 1 profile Removing oil seals 15 Installing sleeve 4112 893 2400 Installing oil seal 16 Press sleeve 4112 893 2401 Installing oil seal at starter side 17 Press sleeve 1115 893 4600 Installing oil seal at clutch side 18 Wrench 13mm 5910 893 5608 Removing starter cup fanwheel 19 Combination wrench 4180 890 3400 Spark plug 20 Assembly drift 1108 893 4700 Removing piston pin 21 Assembly drift 1114 893 4700 Installing piston pin 22 Setting gauge 4118 890 6401 Setting air gap for ignition 23 Screwdriver 5910 890 2301 Screws 24 Test line 1110 141 8600 Carburetor leakage test 25 Nipple 0000 855 9200 Carburetor leakage test 26 Removing tool 5910 890 4602 Removing clutch drum 27 Puller 5910 890 4501 Removing limiter cap 28 Test flange 1119 850 4201 Leakage test 29 Sleeve 0000 963 1008 Leakage test 30 Sealing plate 0000 855 8106 Sealing exhaust port 31 Ignition system tester ZAT 4 5910 850 4503 Testing ignition 32 Ignition system tester ZAT 3 5910 850 4520 Testing ignition 33 Press arbor 4119 89
19. 7 6 2 Assembling and Installing IES ans Re AEN T TSO NI PERPAR LA WS CY Cn A ay 235RA005 VA Attach spring to clutch shoes Kay 249RA067 VA Fit corrugated washers 1 and 2 YY Fit screws 1 and 2 and tighten them down firmly 3 4 Place cover plate 1 with 1 facing up on the flywheel RER Q Fit sleeves 1 and 2 on cover plate and press into the flywheel 249RA066 VA 38 Fit clutch shoes with lettering facing up Fit the cover plate with 2 facing up Fit the fan housing on the engine Tighten down the screw 1 firmly 1 3 4 Series 4180 Powerhead 7 6 3 Clutch Drum and Bearing lt x gt ite Ge lt x oc a A Remove the engine 7 6 1 Removing the retaining ring 1 Different fan housings are fitted to the powerhead Pressure die cast fan housing Polymer fan housing Differences in removal and installation procedures are described below a a q w a t Polymer fan housing Support the ball bearing at the clutch drum 2 side with removal tool 5910 890 4602 1 Series 4180 Powerhead Turn the removal tool and fan housing over so that the fan housing rests on the removal tool All models 249RA136 VA Insert extension 4180 893 4400 1 in square hole and use bench press to push out clutch drum in direction of engine Remove the bearing
20. 9RA004 VA Remove the rewind starter 5 2 Take out the screws 1 and 2 Carefully pull off the spark plug boot 3 vertically Take out the screw 1 Remove the shroud upwards and pull the spark plug boot through the shroud at the same time Install in the reverse sequence Tighten down the screws 3 4 Series 4180 Powerhead 6 Fuel System 6 1 Air Filter Dirty and clogged air filters reduce engine power increase fuel consumption and make starting more difficult The air filter must be cleaned when there is a noticeable loss of engine power Close the choke shutter Clean away any loose dirt from around the filter and filter cover mT x7 249RA005 VA Loosen the slotted screw 1 and lift away the filter cover 249RA006 VA Remove the filter 1 The filter element is not washable If itis heavily loaded with dirt fit anew one Series 4180 Powerhead Take out the screws 1 and 2 Remove the air filter housing Remove the paper gasket 1 and fit a new one When reassembling check that the air filter housing is of the right type 249RA183 BL Air filter housing A without stub for tank vent without return line 6 5 Air filter housing B with stub arrow for tank vent with return line to clean air side 6 5 Install air filter housing B with stub only with connecting hose to
21. FC 90 FC 95 FC 100 FC 110 FS 90 FS 100 FS 110 FS 130 STIHL HL 100 HT 100 HT 101 KM 90 KM 100 KM 110 KM 130 Contents 1 Introduction Safety Precautions Specifications Engine Spark Plug Fuel System Tightening Torques Troubleshooting Clutch Rewind Starter Ignition System Carburetor Engine Rewind Starter Shroud General Removing and Installing Rope Rotor Starter Rope Tensioning Pawl Replacing the Rewind Spring Removing the Shroud Fuel System Air Filter Carburetor Leakage Test Removing and Installing Manual Fuel Pump Metering Diaphragm Inlet Needle Fixed Jet Pump Diaphragm Accelerator Pump Adjusting Idle Speed Basic Setting Series 4180 Powerhead N AAA A n NOOO ON 6 5 6 5 1 6 5 2 6 6 1 6 6 2 6 6 3 7 1 7 2 7 3 7 4 7 4 1 7 5 7 6 7 6 1 7 6 2 7 6 3 7 7 7 8 1 7 8 2 78 3 784 785 7 10 7 11 Tank Vent Checking Operation Replacing Tank Vent Fuel Supply Cleaning the Fuel Tank Fuel Hoses and Pickup Body Fuel Tank Engine Compression Pressure Checking Adjusting Valve Clearance Rocker Arms Pushrods Cam Followers Cam Gear Decompression System Muffler Spark Arresting Screen Clutch Removing and Disassembling Assembling and Installing Clutch Drum and Bearing Flywheel Crankshaft Replacing the Oil Seals Crankcase Lower Half Crankshaft Piston Piston Rings Valves Valve Springs Upper Half
22. 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 Improper handling may result in burns or other serious injuries If parts are heated during servicing work always wear suitable protective gloves Do not bring any fire flame spark or other source of heat near the fuel All work with fuel must be performed outdoors only Spilled fuel must be wiped away immediately Check for leaks after performing any work on the fuel system or engine Series 4180 Powerhead 3 Specifications 3 1 Engine Displacement Bore Stroke Engine power to ISO 8893 Max permissible engine speed with cut off by ignition module FS 90 FC 90 95 KM 90 FS 100 110 FC 100 110 HT 100 101 HL 100 KM 100 110 FS 130 KM 130 STIHL single cylinder four stroke engine with mixture lubrication 28 4 cm 38 mm 25 mm 0 95 kW at 7 000 rpm 10 500 500 rpm 31 4 cm 40 mm 25 mm 1 05 kw at 7 000 rom 10 500 500 rpm 36 3 cm 43 mm 25 mm 1 4 kw at 8 500 rpm 10 500 500 rpm Idle speed 2 800 rpm 2 800 rpm 2 800 rom Clutch Centrifugal clutch two clutch shoes without linings Clutch engages at 3 700 rpm 3 700 rpm 3 700 rpm Valve clearance Inlet valve 0 10 mm 0 10 mm 0 10 mm Exhaust valve 0 10 mm 0 10 mm 0 10 mm Valve diameter 13 5 mm 13 5 mm 15 5 mm Marking A A Bor E 2
23. at the bottom end of the slot arrow If the slide is not at the end of the slot 59 Use a screwdriver to push the slide to the bottom end of the slot 249RA200 BL Push down the interlock lever 1 and squeeze the throttle trigger 2 as far as stop full throttle position Throttle cable tension is adjusted automatically in this process 249RA201 BL The slide arrow moves away from the bottom of the slot Check the adjustment 9 3 3 60 If the lever does not butt against the stop Readjust tensioner until the lever butts against the respective stops Adjust the throttle cable and check the adjustment again 9 3 3 Fit the shroud Control Handle without Slide 9 3 2 Remove the shroud 5 7 Adjust idle speed screw correctly 249RA197 BL Screw the tensioning screw 1 into the tensioner 2 until equal lengths of thread arrows are visible above and below the tensioner Check the adjustment 9 3 3 If the lever does not butt against the stop Adjust the tensioning screw 1 on the tensioner 2 and check the adjustment again Repeat this procedure until the lever butts against the respective stops when the throttle trigger is in the idle and full throttle positions Fit the shroud Series 4180 Powerhead 9 3 3 Checking Adjustment Throttle lever must butt against the stop o
24. buretor air filter and ignition system before looking for faults on the engine Lubricate all moving parts of the engine with oil Exceptions are described separately 31 7 1 Compression Pressure 249RA138 VA Pull off the spark plug boot Unscrew the spark plug Screw compression tester 5910 850 2000 1 into the spark plug hole Move slide control to STOP 0 Set choke shutter to open Pull starter rope vigorously and quickly several times Note compression pressure If the compression pressure is below 6 bar check valve clearance and readjust if necessary 7 2 If this produces no improvement check the cylinder valve seat piston and piston rings for scores or other damage The design specification is 6 7 bar Reassemble in the reverse sequence 32 7 2 Checking Adjusting Valve Clearance Check and adjust valve clearances only when engine is cold Remove the rewind starter 5 2 Remove the shroud 5 7 Take out the screw 1 Remove the sealing ring Unscrew the spark plug Remove the valve cover 1 Remove the gasket 2 gt o a q oc a Rotate the crankshaft until the arrow 1 is in line with the screw 2 on the right hand side of the ignition module Observe rocker arms while rotating the fanwheel up to the mark If the valves are operated by the rocker arms in this positio
25. ckwise Fit new clutch Fit new clutch 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 Normal wear Fit new starter rope Fit new starter rope Rewind spring broken starter rope does not rewind Spring overtensioned no reserve when rope is fully extended Very dirty or corroded Fit new rewind spring 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 Spring clip fatigued Fit new pawl Fit new spring clip Starter rope is difficult to pull and rewinds very slowly Starter mechanism very dirty dusty conditions Lubricating oil on rewind spring becomes viscous at very low outside temperatures spring windings stick together Thoroughly clean complete starter mechanism 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 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 does not run No spark Spark plug dirty or
26. e clutch drum 2 side with removal tool 5910 890 4602 1 62 Turn the removal tool and fan housing over so that the fan housing rests on the removal tool All models 249RA187 BL Remove the sleeves 1 together with rubber mounting Insert extension 4180 893 4400 2 in square hole in clutch drum 249RA133 VA Apply puller 59010 890 4400 1 with No 2 jaws and clamp the arms Jaws must engage cutouts in the clamp 1 Pull clamp 1 with rubber element 2 out of fan housing Coat rubber element and rubber mounting of sleeves with press fluid 12 Push rubber element into clamp first then press it into the fan housing The rubber element with clamp is recessed about 2 mm in the fan housing It is therefore necessary to use press sleeve 4119 893 2400 for this operation Reassemble all other parts in the reverse sequence Series 4180 Powerhead 11 Special Servicing Tools No Part Name Part No Application 1 Assembly stand 5910 890 3100 Holding powerhead for servicing repairs 2 Clamp 5910 890 8800 for No 1 3 Compression tester 5910 850 2000 Testing valves and piston rings for leaks 4 Locking screw 4180 890 2700 Blocking the crankshaft 5 Extension 4180 893 4400 Removing AV element and clutch drum 6 Press arbor 4119 893 2400 Removing installing clutch drum bearing 7 Installing tool 5910 890 2206 Snap ring on piston pin 8 Installing tool
27. eakerless ignition system basically consists of an ignition module 1 and flywheel 2 Series 4180 Powerhead Use suitable pliers to pull the leg spring out of the spark plug boot Unhook the leg spring from the ignition lead Push the spark plug boot back a little in the direction of the ignition module Take about 10 mm off the end of the ignition lead Coat end of ignition lead with oil Pull the lead back into the boot so that the leg spring locates properly inside it Reassemble in the reverse sequence lt gt fe lt a S ire N Check if spark plug has a detachable adapter nut arrow If so make sure it is properly fitted and firmly tightened 51 8 2 Ignition Module A lt ite a lt x D A The ignition module accommodates all the components required to control ignition timing There are three electrical connections on the coil body High voltage output with ignition lead 1 Connector tag 2 for the short circuit wire Connector tag 3 for the ground wire Accurate testing of the ignition module is only possible with special test equipment For this reason it is only necessary to carry out a spark test in the workshop A new ignition module must be installed if no ignition spark is obtained after checking that wiring and stop switch are in good condition 52 8 2 1 Ignition Timing Igniti
28. econdary air seepage through faulty gaskets on spacer flange Piston rings worn or broken Muffler spark arresting screen carbonized Air filter element dirty Fuel impulse line kinked or cracked Pump diaphragm torn Decompression lever sticking Install new gaskets Install new piston rings Clean muffler inlet and exhaust openings replace spark arresting screen if fitted Fit new air filter element Fit new lines or position without kinks Install new pump diaphragm Install new cam gear 12 Series 4180 Powerhead Condition Cause Remedy Engine overheating Insufficient cylinder cooling Air inlets in fan housing blocked or cooling fins on cylinder very dirty Thoroughly clean all cooling air passages and cooling fins Series 4180 Powerhead 13 5 Rewind Starter Shroud 5 1 General If the action of the starter rope becomes very stiff and the rope rewinds very slowly or not completely it can be assumed that the starter mechanism is in order but plugged with dirt At very low outside temperatures the lubricating oil on the rewind spring may thicken and cause the spring windings to stick together This has a detrimental effect on the function of the starter mechanism In such a case it is sufficient to clean the rewind spring with a standard commercial cleaner and then coat it with resin free oil Pull out the starter rope several times and allow it to rewind until i
29. esting screen if fitted and clean or replace as necessary The limiter caps must not be removed for the standard setting Corrections to the high speed screw H 1 and low speed screw L 2 are only possible within fine limits Unscrew the high speed screw H counterclockwise as far as stop no more than 3 4 turn Unscrew the low speed screw L counterclockwise as far as stop no more than 3 4 turn Start the engine and allow it to warm up Use the idle speed screw LA 3 to adjust engine idle speed Turn clockwise to increase engine speed turn counterclockwise to reduce engine speed 25 Adjust engine idle speed with the aid of a tachometer 3 1 note that there is an ignition spark on every revolution of the crankshaft Check idling behavior by opening the throttle several times Make sure engine idles and accelerates smoothly If the engine stops while idling Turn the idle speed screw clockwise until the tool begins to move Then turn the screw back one quarter of a turn from that position If the tool runs while the engine is idling Turn idle speed screw counterclockwise until the tool stops running Then turn the screw about another quarter turn in the same direction A slight correction of the setting of the high speed screw H may be necessary no further than stop if engine power is not satisfactory when ope
30. faulty Faulty insulation or break in ignition coil ignition lead or short circuit wire Check operation of slide control and ignition module replace damaged parts Clean or replace spark plug Use ohmmeter to check ignition coil and lead for break If break is detected or resistance is high fit new ignition coil and ignition lead check short circuit wire for ground contact in run position Engine runs roughly misfires temporary loss of power Spark plug boot is loose Spark covered in soot smeared with oil Weak spark or no spark Wrong air gap between ignition coil and flywheel Flywheel cracked or damaged Check operation of spark plug Check slide control ignition coil wire for damaged insulation and leakage current Press boot firmly onto spark plug and fit a new leg spring if necessary Install new spark plug 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 Reset air gap Install new flywheel Clean or replace spark plug replace damaged parts of ignition system 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 Inlet control lever sticking on spindle Helical spring not located on nipple of inlet control lever Perforated disc o
31. fit the fuel hoses Reassemble all other parts in the reverse sequence However if the pressure drops there are two possible causes 1 The inlet needle is not sealing foreign matter in valve seat or sealing cone of inlet needle is damaged or inlet control lever sticking 2 The metering diaphragm is damaged In either case the carburetor must be removed and serviced 6 2 After completing test open the vent screw on the carburetor and crankcase tester and disconnect the test hose from the carburetor Series 4180 Powerhead 6 2 2 Removing and Installing Remove the air filter 6 1 Pull the fuel hoses 1 and 2 off the elbow connectors Disconnect throttle cable nipple 1 from slotted pin 2 on the throttle lever Pull the impulse hose 1 off the metering diaphragm Series 4180 Powerhead e Pull carburetor off the studs Remove the gasket 1 Disconnect the cable 2 If spacer flange shows signs of damage or cracks install a new one 7 10 Reassemble in the reverse sequence 249RA017 VA 6 2 3 Manual Fuel Pump 249RA108 VA Remove the shroud 5 7 Perform leakage test 6 2 1 Take out the screws 1 Remove end cover together with rubber pump bulb Remove rubber bulb from the end cover 21 249RA110 VA Remove the flange Examine the metering diaphragm and sealing ring Replace if necessary 6 2 4
32. gnition system before looking for faults on the engine 4 1 Remove the lower half of the crankcase 7 8 2 Lift the crankshaft 1 and pull the piston out of the cylinder at the same time Pull off the oil seals 2 and 3 Inspect cylinder running face for signs of damage and serious scores Install new cylinder if necessary Q 7 10 eH N is lt oc a A Examine ball bearings 1 connecting rod 2 and gear 3 f one of these parts is damaged install a new crankshaft assembly Coat piston and piston rings with oil Fit piston rings so that their gaps are offset 120 degrees Use new oil seals Lubricate sealing lips of oil seal with grease 12 Apply thin coating of sealant to outer diameter of oil seal 12 Fit oil seals over crankshaft with their open sides facing inwards Carefully fit piston in the cylinder Install the crankshaft with new oil seals Fit lower half of crankcase 7 8 2 Fit the flywheel 7 7 Series 4180 Powerhead lt x gt o v lt x oc a iN Rotate flywheel until mark 1 isin line with screw head 2 Adjust valve timing 7 4 Series 4180 Powerhead 7 8 4 Piston Remove the crankshaft 7 8 3 Important Wear safety glasses when working with spring washers and snap rings Ease the hookless snap ring out of the groove i lt gt
33. he tank vent Coat O ring and bead of new tank vent with press fluid 12 Center the new tank vent in the bore and push it home as far as stop it must snap into position Tank vent with return line Push hose 1 onto stub on filter housing 3 Installing tank vent with return line in a machine that has a filter housing without stub Pull hose 1 off the tank vent Both tank vent systems Test new tank vent for leaks 6 5 1 Fit both fuel hoses on the carburetor Series 4180 Powerhead 6 6 Fuel Supply The diaphragm pump draws fuel out of the tank and into the carburetor via the fuel hose Any impurities mixed with the fuel are retained by the pickup body The fine pores of the pickup body eventually become clogged with minute particles of dirt This restricts the passage of fuel and results in fuel starvation In the event of trouble with the fuel supply system always check the fuel tank and the pickup body first Clean the fuel tank if necessary 6 6 1 After completing servicing work on the fuel system Test the fuel system for leaks 6 5 1 Series 4180 Powerhead 6 6 1 Cleaning the Fuel Tank lt gt oO ise q lt aa a A Unscrew the filler cap 1 and drain the tank Pour a small amount of clean gasoline into the tank and shake the unit vigorously Open the tank again and drain it Dispose of fuel properly at an ap
34. ide the setting gauge 4118 890 6401 2 between the arms of the ignition module 1 and the flywheel 3 Press the ignition module against the setting gauge Tighten down the screws 3 4 Reassemble all other parts in the reverse sequence To test the ignition module use either the ZAT 4 ignition system tester 5910 850 4503 or the ZAT 3 ignition system tester 5910 850 4520 The ignition test refers only toa spark test not to ignition timing 53 8 3 Testing the Ignition System 208RA053 VA 208RA054 VA Using the ZAT 4 ignition tester 5910 850 4503 Before starting the test install a new spark plug in the cylinder and tighten it down firmly EQ 3 4 Pull the boot off the spark plug and connect it to the input terminal 1 Push the tester s output terminal 3 onto the spark plug Crank the engine quickly with the rewind starter min 1 000 rpm and check spark in the tester s window 2 The engine may start and accelerate during the test If a spark is visible the ignition system is in order If no spark is visible in the window 2 Check ignition system with aid of troubleshooting chart 8 4 54 Using ZAT 3 ignition system tester 5910 850 4520 Before starting the test install a new spark plug in the cylinder and tighten it down firmly G2 3 4 Pull the boot off the spark plug and connect it to terminal 2 Attach ground terminal 1 to
35. k Check air gap and reset if necessary Check flywheel Have pole shoes turned blue Install new flywheel Disconnect short circuit wire from ignition module Check ignition lead Severe chafing Spark plug boot Holes cracks Resistance spark plug boot to ground spec 1 5 12kO Check resistance of ignition lead spec lt 10 Q If necessary install new spark plug boot and or ignition lead if ignition lead is molded to ignition module Install new ignition module Series 4180 Powerhead Check operation of slide control or separate stop switch Short circuit wire chafed Contact gap contact springs If necessary install new ignition lead and or contact springs microswitch Re connect short circuit wire Powerful spark Install new ignition module Check I STOP O function on slide control or separate stop switch Series 4180 Powerhead Look for fault in fuel system or carburetor check engine for leaks check position of flywheel on crankshaft 57 9 Throttle Control Throttle Trigger Interlock Lever 9 1 Use a screwdriver to push the slide if fitted to the bottom end of the slot arrow To avoid the risk of electrocution do not start the unit while the control handle is open Take out the screws arrows
36. key for damage and replace key or flywheel if necessary Mount puller 1 4119 890 4501 to the flywheel with M6 x 25 screws 2 and 3 and pull off the flywheel q gt a N S q a A Flywheel 1 and magnet poles 2 must show no signs of cracks or other damage If this is the case install a new flywheel Fit the flywheel in position Check that flywheel is properly seated Key 1 in flywheel must engage slot in crankshaft stub 249RA071 VA Fit the hex nut 1 and tighten it down firmly G2 3 4 Install the clutch 7 6 2 Series 4180 Powerhead 7 8 Crankshaft 7 8 1 Replacing the Oil Seals It is not necessary to disassemble the complete engine to replace leaking oil seals Starter side Remove the rewind starter m 5 2 Use combination wrench 4180 890 3400 to remove the spark plug Fit locking screw 4180 890 2700 1 Rotate crankshaft counter clockwise until the piston butts against the locking screw Series 4180 Powerhead Remove the hex nut 1 Remove the starter cup 2 Apply puller 5910 890 4400 1 with No 3 1 jaws and clamp the arms Pull out the oil seal Take special care not to damage the crankshaft stub Installing oil seal at starter side Inspect crankshaft running face for scores Clean sealing face in crankcase Lubricate sealing lips of oil seal with grease 12 Apply thin coating
37. l handle 5 0 2 Spline socket screw IS DG4x18 Cover cylinder 4 5 Spline socket screw IS M5x21 Filter cover filter housing 3 5 Collar nut M8 Filter housing carburetor 3 5 Spline socket screw IS D5x24 Gear housing drive tube 8 0 Spline socket screw IS M4x9 5 Screen muffler 2 0 Spline socket screw IS M5x24 Shroud cylinder 6 0 Collar screw M5x16 Rocker lever collar screw cylinder 9 0 Spline socket screw 1S M6x30 Clamp drive tube handle support 8 0 1 Screw M6x30 Coupling sleeve wingscrew 6 0 3 Spline socket screw 1S M6x25 Coupling sleeve nut clamp 9 0 3 Spline socket screw IS DG5x24 Engine pan cylinder 9 0 Spline socket screw IS M6x25 Clamp loop handle nut 4 5 2 Spline socket screw IS P5x14 Fan housing axial location of clutch drum bearing 4 0 Spline socket screw IS DG5x24 Fan housing shroud engine pan 6 0 Spline socket screw IS DG5x24 Fan housing engine pan 6 0 Screw P3 5x9 Detent spring slide control 11 Spline socket screw IS M5x23 Loop handle clamp drive tube 6 0 4 Spline socket screw IS DG5x24 Muffler crankshaft 9 0 Spline socket screw IS DG5x24 Muffler cylinder 9 0 Spline socket screw IS M5x16 Cutting tool deflector gear housing 4 5 Nut M8x1 Flywheel crankshaft 17 0 Spline socket screw IS M6x14 Clampj carrying ring 45 Spline socket screw IS M5x12 Clamp drive tube fan housing 6 0 Spline socket screw IS DG5x24 Starter cover cover engine pan 6 0 Series 4180 Powerhead Fastener Thread size For component Torque Spline socket screw IS
38. ly thin coating of sealant to outside diameter of oil seal 12 e Push on the oil seal as far as the crankcase Note the installed position Closed side of the oil seal must face flywheel Series 4180 Powerhead Press home the oil seal 1 with press sleeve 4112 893 2401 2 so that it is flush with the crankcase Remove the installing sleeve Fit the flywheel 7 7 Install the clutch G2 7 6 2 Remove the locking screw 4180 890 2700 Fit spark plug and tighten it down firmly GQ 3 4 Fit the shroud 5 7 Fit the rewind starter 5 2 Series 4180 Powerhead 7 8 2 Crankcase Lower Half Remove the tank 6 6 3 Remove the muffler 7 5 Remove the flywheel 7 7 Take out the screws arrows Lift away the lower half of the crankcase lt x gt o N S q lt a a SA A Do not take the crankshaft out of the bearings because this will alter cam gear timing 7 4 Install in the reverse sequence Clean the sealing face 1 of the upper half of the crankcase and the oil seals Clean the sealing face of the lower half of the crankcase Check oil seals for leaks damage and cracks 43 Apply thin coating of sealant to gaskets faces 12 Tighten down screws arrows in crosswise pattern 3 4 44 7 8 3 Crankshaft Always check and if necessary repair the fuel system carburetor air filter and i
39. n valve overlap rotate the crankshaft another turn until the valves are idle and the arrow 1 lines up with the screw 2 Make sure the valves are not operated in this position by turning the crankshaft back and forth If there is no noticeable valve overlap proceed as follows Series 4180 Powerhead Fit locking screw 1 4180 890 2700 in spark plug hole Take out the screws arrows Carefully lift away the cam gear cover 1 Marks arrows on 2 and 3 must line up with the notches 1 and 4 in the cylinder Rotate crankshaft counter clockwise until the piston butts against the locking screw Remove the hex nut 1 Remove the starter cup 2 Remove the locking screw Series 4180 Powerhead Rotate crankshaft clockwise until cam lobe points downward lt gt o z lt x a a Check that arrow 1 lines up with the right hand screw 2 on the ignition module Cam gear cover must be fitted before checking and adjusting valve clearances Insert feeler gauge 4180 893 6400 2 between rocker arm and valve stem The feeler gauge must slip through with a certain resistance Inlet valve 1 0 10 0 02 mm Exhaust valve 3 0 10 0 02 mm 33 Adjusting Valves Valve clearance is adjusted with the locknuts 1 and 2 To increase valve clearance Turn nut counterclockwise To reduce valve clearance Turn nut clockwise
40. n diaphragm is deformed and presses constantly against inlet control lever Inlet control lever too high relative to design position After more than five starting attempts with choke shutter closed Remove and clean or replace inlet needle clean fuel tank pickup body and fuel line if necessary Free off inlet control lever Remove inlet control lever and refit correctly Fit new metering diaphragm Set inlet control lever flush with upper face of housing or bottom of metering chamber Open choke shutter after no more than five starting attempts Poor acceleration Idle jet too lean Main jet too lean Inlet control lever too low relative to design position Inlet needle sticking to valve seat Connecting bore to atmosphere blocked Diaphragm gasket leaking Metering diaphragm damaged or shrunk Back off low speed screw slightly Back off high speed screw slightly Set inlet control lever flush with upper face of housing or bottom of metering chamber Remove inlet needle and clean valve seat Clean bore Fit new diaphragm gasket Fit new metering diaphragm 10 Series 4180 Powerhead Condition Cause Remedy Engine will not idle idle speed too high Throttle shutter opened too wide by idle speed screw Intake stub leaking Reset idle speed screw LA Seal or replace intake stub Engine stalls at idle speed Idle jet bores or ports blocked Idle jet too rich Setting
41. n the carburetor cover when the throttle trigger is squeezed as far as stop full throttle and butt against the idle speed screw LA when the throttle trigger is in the idle position Check as follows 249RA202 BL Let go of throttle trigger idle position The lever 1 must butt against the idle speed screw arrow 249RA203 BL Push down the interlock lever and pull the throttle trigger all the way full throttle position The lever 1 must butt against the stop arrow Series 4180 Powerhead 9 4 Slide Control Remove the interlock lever 9 1 Pull slide control off the handle molding Remove screws arrows from clamps Remove the handle molding from the drive tube 249RA10 Remove the torsion spring from the pivot 249RA107 VA Take out the switch 1 Reassemble in the reverse sequence Position wire for switch in the guide 2 61 10 AV System LA E 249RA131 V Remove the engine 7 6 1 Take screw 1 out of fan housing Remove the fan housing Different fan housings are fitted to the powerhead Pressure die cast fan housing Polymer fan housing Differences in removal and installation procedures for the clutch drum and bearing are described in the appropriate chapter a a a a yt Polymer fan housing Support the ball bearing at th
42. of Crankcase with Cylinder Leakage Test 29 31 31 32 32 34 35 36 36 37 37 38 48 49 49 8 Ignition System 8 1 Spark Plug Boot 8 2 Ignition Module 8 2 1 Ignition Timing 8 2 2 Removing and Installing 8 3 Testing the Ignition System 8 4 Ignition System Troubleshooting 9 Throttle Control 9 1 Throttle Trigger Interlock Lever 9 2 Tensioner 9 3 Adjusting Throttle Cable 9 3 1 Control Handle with Slide 9 3 2 Control Handle without Slide 9 3 3 Checking Adjustment 9 4 Slide Control 10 AV System 11 Special Servicing Tools 12 Special Accessories STIHL 51 51 52 52 52 54 55 58 63 64 ANDREAS STIHL AG amp Co KG 2006 1 Introduction 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 of 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
43. on timing is not adjustable Since there is no mechanical wear in these systems ignition timing cannot get out of adjustment However an internal fault in the circuit can alter the switching point in such a way that a spark test will still show the system to be in order although timing is outside the permissible tolerance This will impair engine starting and running behavior 8 2 2 Removing and Installing Remove the shroud 5 7 Disconnect throttle cable nipple 1 from the slotted pin 2 on the throttle lever Pry the cable 1 out of the spacer flange Pull the short circuit wire 2 and ground wire 3 off the ignition module Series 4180 Powerhead lt x gt o q oc a A Take out screw 1 on fan housing and lift away the engine Support the engine while removing the screw Release and remove screw 1 with connector tag Take out the screw 2 with washer Remove the ignition module Series 4180 Powerhead Depending on the type of cylinder the ignition module is mounted to the cylinder with or without washers The height of the cylinder bosses for mounting the ignition module are different a 6 7 mm Mount ignition module without washers a 4 7 mm Mount ignition module with washers E a 8 rd S In this case fit the washers 1 between the cylinder and ignition module Both models Sl
44. ope tensioned Let go of the rope rotor and slowly release the starter grip so that the rope winds itself onto the rotor ma 249RA156 VA The starter grip must sit firmly in the rope guide bush without drooping to one side If this is not the case tension the spring by one additional turn When the starter rope is fully extended it must still be possible to rotate the rope rotor at least another half turn before maximum spring tension is reached If this is not the case pull the rope out hold the rope rotor steady and take off one turn of the rope Install the rewind starter 5 2 17 Ease the spring clip 1 off the starter post Do not take the rope rotor off the starter post Pull the pawl 2 out of the rope rotor Lubricate peg of new pawl with grease 12 18 5 6 Replacing the Rewind Spring Remove the rope rotor 5 3 The pieces of broken spring may still be under tension and may fly apart unexpectedly when you remove them Wear face protection and gloves to reduce the risk of injury Remove the spring housing and parts of the spring Lubricate the new spring with a few drops of resin free oil Position the new spring housing bottom plate must face up as shown arrows and push it home Install the rope rotor 5 3 Fit the starter rope 5 4 Reassemble all other parts in the reverse sequence 5 7 Removing the Shroud 24
45. oremove the muffler take out the screws arrows Remove the exhaust gasket 1 Reassemble in the reverse sequence Use a new exhaust gasket Tighten down muffler mounting screws 3 4 Tighten down the cover screws 3 4 Series 4180 Powerhead 7 6 Clutch 7 6 1 Removing and Disassembling Troubleshooting chart 4 1 Remove the shroud 5 2 Remove the throttle cable and wiring of ignition module 8 2 2 lt gt f lt oc a A Take the screw 1 out of the fan housing and remove the engine Support the engine so that it does not drop when the screw is removed Series 4180 Powerhead 148RA101 VA Inspect the clutch drum 1 There should be no scores or signs of excessive wear If there are signs of serious wear on the inside diameter of the clutch drum check the remaining wall thickness If it is less than about 80 of the original thickness fit a new clutch drum 7 6 3 249RA061 VA Take out the clutch shoe screws 1 and 2 Remove the cover plate 3 Remove the clutch shoes 1 together with the spring 2 and lower cover plate Remove the spark plug Fit the locking screw 4180 890 2700 Rotate the crankshaft counter clockwise until the piston butts against the locking screw Tilt the clutch shoes and unhook the spring Clutch shoes must always be replaced in pairs 37
46. proved disposal site 6 6 2 Fuel Hoses and Pickup Body Depending on the type of fuel tank two different fuel supply systems are installed One part system molded hose grommet and fuel hoses are in one piece Multi part system connector and fuel hoses are available as separate items Differences in removal and installation procedures are described below Pull the fuel hoses off the carburetor 6 2 2 a z3 BESA A One part system Carefully pry the grommet 1 out of the fuel tank taking care not to damage the tank lt x gt o ise q lt oc a FA A Remove the fuel hoses with the pickup body 29 249RA176 BL Multi part system Carefully pry the tab 1 of the connector upwards take care not to damage the fuel 249RA177 BL Pull the connector 1 with hoses 2 3 molded hose 4 and pickup body out of the tank All systems i a 2 S a Pull the pickup body 1 off the molded hose 2 Replace damaged parts Make sure the new fuel supply system suits the machine s fuel tank 30 Install in the reverse sequence Attach pickup body with molded hose to connector f Press Fluid lt E OH 723 Coat O ring 1 and bead of connector or grommet on molded hose one part system with press fluid 12 One part system Mark on fuel hose grommet must line up with mark on tank a a
47. q A Multi part system Center the connector in the fuel tank s opening and turn it so that the tab 1 fits in the cutout 2 Push home the connector as far as stop it must snap into position All systems Check that hoses are properly connected 249RA182 BL Suction hose 1 from hose connector with choke symbol to fuel intake stub 2 Hose 3 from connector 4 to return stub 5 Series 4180 Powerhead 6 6 3 Fuel Tank Drain the fuel tank Remove the rewind starter 5 2 Remove the shroud 5 7 Remove the air filter 6 1 Pull the fuel hoses off the carburetor 6 2 2 Pry the fuel hose with pickup body out of the tank 6 6 2 Pry the tank vent out of the tank 6 5 2 Unscrew the fuel filler cap and remove it together with the cap retainer q gt o ise lt ac a a A Pull out the fuel tank with sleeves 1 and 2 Series 4180 Powerhead lt x gt i t gt q oc D A Remove the sleeves 1 and 2 Reassemble in the reverse sequence The new fuel tank is supplied with a tank vent with return line and the required hose If the new fuel tank is combined with an original filter housing without stub for the return line 6 1 pull the hose off the tank vent 6 5 2 Test the fuel tank for leaks 6 5 1 7 Engine Always check and if necessary repair the fuel supply car
48. rating at high altitude sea level or after changing the cutting tool Turn the high speed screw H clockwise leaner at high altitude or counterclockwise richer at sea level The limiter caps only need to be removed from the screws if it is necessary to replace the high speed screw H or low speed screw L clean the carburetor or carry out the basic setting 6 4 1 26 6 4 1 Basic Setting lt gt lt ira 5 Dt a Remove the limiter caps to carry out the basic setting Push the puller 5910 890 4501 1 with the groove facing you between the limiter cap 2 and carburetor body Pry off the cap If the limiter cap is stuck on the adjusting screw turn the puller over so that its groove faces the carburetor body Pry off the limiter cap The basic setting must be carried out after removing the limiter caps Do not re install used caps because they may have been damaged during the removal process 249RA165 VA Carefully screw the high speed screw H 1 and low speed screw L 2 clockwise down onto their seats The basic setting is carried out with the high speed screw H and the low speed screw L as follows FS 90 FC 90 95 KM 90 C1Q S110 Open the high speed screw H 1 turn counterclockwise Open the low speed screw L 3 5 turns counterclockwise FS FC KM 100 110 HT 100 101 C1Q S72 C1Q S81 C1Q S88 Open the
49. re the inlet needle and spring are properly seated Series 4180 Powerhead Remove the metering diaphragm 6 2 4 Use a suitable screwdriver to unscrew the fixed jet 1 Reassemble in the reverse sequence Take care not to damage the fixed jet with the screwdriver during assembly and installation Remove the carburetor 6 2 2 Take out the screws 1 Remove the end cover 2 Remove the spring 1 and spring retainer 2 from the diaphragm 23 Remove the gasket 1 and pump diaphragm 2 If the gasket and diaphragm are stuck together separate them carefully Check diaphragm and gasket and replace if necessary The diaphragm is the most delicate part of the carburetor It is subjected to continuous alternating stresses and the material eventually shows signs of fatigue i e the diaphragm distorts and swells and has to be replaced lt gt S g Remove flange body 1 with idle speed screw 24 Remove the gasket 1 and pump diaphragm 2 Reassemble in the reverse sequence The pump diaphragm 1 and gasket 2 are held in position by the cast pegs on the flange body with idle speed screw 3 Gasket 1 and pump diaphragm 2 are held in place by the cast pegs on the end cover 5 Install the spring 4 and spring retainer 3 in the housing base 5 Fit the diaphragm 2 and gasket 1 and screw the assembly
50. s of the pins 1 Different lengths of pins have to be installed to suit the type of cylinder Cylinders have bearing bores of different depths Series 4180 Powerhead Permissible combinations are as follows Bore Length of pin a 12 2 mm 28 mm b 5 7 mm a 10 7 mm 26 5 mm b 4 2 mm Set crankshaft to T D C 7 8 3 Fit the cam gear so that the marks 1 and 2 and 3 and 4 are in alignment Install the pin 1 The marks must not move out of position while the cam gear is being fitted Install the left hand cam follower first It controls the inlet valve 35 7 4 1 Decompression System Remove cam gear cover 7 2 Check free movement and function of decompression system lever arrow Lever must project about 2 mm from cam Push decompression system lever counterclockwise The lever must move freely and retract fully If the lever is difficult to move worn or not visible install a new cam gear 36 7 5 Muffler Spark Arresting Screen lt gt o irs is lt oc a A Remove the rewind starter 5 2 Remove the shroud 5 7 Take out the screws arrows Remove the cover 1 lt gt vey 3 lt ira S Take out the screw if fitted lift up the spark arresting screen 1 and pull it out Clean the spark arresting screen or if necessary install a new one T
51. ssure gauge indicates a vacuum of 0 5 bar If the vacuum reading remains constant or drops to no more than 0 3 bar within 20 seconds it can be assumed that the oil seals are in good condition If the vacuum drops to less than 0 3 bar within 20 seconds the oil seals are defective and have to be replaced 7 8 1 249RA193 BL Pressure test Connect pressure hose 1 of tester 1106 850 2905 to nipple 2 on test flange Close vent screw on the rubber bulb Pump air into the crankcase with rubber bulb until the gauge indicates a pressure of 0 5 bar If this pressure remains constant for at least 20 seconds the crankcase is airtight If the pressure drops the leak must be located and the faulty part replaced To find the leak coat the suspect area with oil and pressurize the crankcase Bubbles will appear if a leak exists Series 4180 Powerhead 8 Ignition System Exercise extreme caution when carrying out maintenance and repair work on the ignition system The high voltages which occur can cause serious or even fatal accidents Troubleshooting on the ignition system should always begin at the spark plug 4 3 8 1 Spark Plug Boot Remove the shroud 5 7 The ignition lead is molded to the ignition module 176RA159 VA 176RA160 VA Pinch the hook of the leg spring into the center of the lead i e about 15 mm from the end of the lead The electronic br
52. tank vent Unfiltered air would be sucked in if the connecting hose is not fitted This would result in an increased rate of wear and a risk of engine damage Reassemble all other parts in the reverse sequence Tighten down screws on air filter housing 3 4 Tighten down screw air on filter cover LA 3 4 19 6 2 Carburetor 6 2 1 Leakage Test Troubleshooting chart 4 4 In the event of trouble with the carburetor first check the fuel supply 6 6 and tank vent 6 5 The carburetor can be tested for leaks with the carburetor and crankcase tester 1106 850 2905 Remove the air filter 6 1 Open the tank filler cap to relieve pressure Close the tank filler cap z 1 Wa We Vgc 7 gt eae 2 2 QU ir wwz g Pull fuel hose 1 off carburetor s elbow connector lt x gt a N lt a G Push the fuel hose 1 1110 141 8600 onto the nipple 2 0000 855 9200 20 ty 1 CI Push the fuel hose 1 with nipple 2 onto the carburetor elbow connector Push the pressure hose of tester 1106 850 2905 onto the nipple Close the vent screw 1 on the rubber bulb Pump air into the carburetor with the rubber bulb 2 until the pressure gauge 3 shows a reading of approx 0 8 bar If this pressure remains constant the carburetor is airtight Disconnect pressure hose and carburetor tester Re
53. the spark plug Use adjusting knob 3 to set spark gap to about 2 mm When using the ZAT 3 hold it only by the handle 4 or position it ina safe place Keep fingers or other parts of body at least 1 cm away from the spark window 3 the high voltage connection 2 ground connection 5 and the ground terminal 1 High voltage risk of electrocution Crank the engine quickly with the rewind starter min 1 000 rpm and check spark in the tester s window 3 The engine may start and accelerate during the test If a spark is visible the ignition system is in order If no spark is visible in the window 3 Check ignition system with aid of troubleshooting chart 8 4 Reassemble in the reverse sequence Series 4180 Powerhead 8 4 Ignition System Troubleshooting Series 4180 Powerhead Engine does not run Slide control in position J or stop switch in position Check the spark plug Smeared with oil black Sooted Electrode gap correct Contacts shorted Clean the plug reset or replace Check spark plug boot Firmly seated on plug leg spring Leg spring hook in center of ignition lead Boot damaged If necessary install new spark plug boot and or leg spring Test ignition system with ZAT 3 or ZAT 4 use ZAT 3 as main spark gap see TI 32 94 55 56 Powerful spar
54. to the carburetor The spring retainer s integrally cast guide points toward the spring 4 Fit the screws and tighten them down firmly Series 4180 Powerhead 6 3 Accelerator Pump 249RA168 VA The carburetor is equipped with an accelerator pump The piston 1 is located in the bore a behind the throttle shaft 2 and is held in the idle position by the spring 3 Filter 4 is fitted in the bore a in front of the throttle shaft 2 to help prevent the ingress of dust Perform the following operations to strip down and clean the accelerator pump Series 4180 Powerhead 249RA169 VA Take out the screw 1 Remove the throttle shutter 2 Remove the E clip 3 Take out the strainer 5 Cover the bore a with one finger Push back the throttle shaft with lever 4 at least 15 mm until the end of the shaft is visible in the choke tube Slowly expose the bore a take out the piston 6 with sealing ring 7 and spring 8 Remove the filter 9 check it for damage and contamination clean it or replace if necessary Inspect piston 6 and spring 8 for damage and replace if necessary Install a new sealing ring 7 in the piston s groove Reassemble all other parts in the reverse sequence 6 4 Adjusting Idle Speed Standard Setting Shut off the engine Check the air filter and replace if necessary Check the spark arr
55. ts normal smooth action is restored 14 5 2 Removing and Installing lt gt S z ira 5 F Remove the screws arrows from the rewind starter Lift away the rewind starter Reassemble in the reverse sequence Tighten down the screws 3 4 5 3 Rope Rotor Remove the rewind starter 5 2 Relieving tension of rewind spring The spring will not be under tension if the starter rope is broken Pull out the starter rope about 20 cm and hold the rope rotor steady lt S z fid g F Engage the rope in the notch on the rotor and make a loop Use the starter rope to turn the rotor clockwise until tension is relieved Series 4180 Powerhead 249RA025 VA To remove the rope rotor ease the spring clip 1 out of the groove in the starter post Remove the washer 2 and pawl 3 Carefully pull the rope rotor 1 off the starter post To replace the rope rotor remove the starter rope 5 4 Series 4180 Powerhead Installing Coat bore in rope rotor with STIHL special lubricant 12 Fit the rope rotor on the starter post so that the driver 1 on the rotor slips behind in the inner spring loop 2 Turn the rope rotor a little and let it go It must spring back Fit the pawl and washer Engage spring clip in the groove on the starter post The spring clip 1 must engage the guide peg 2

STIHL Series 4180 Powerhead

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