STIHL Series 4144 Powerhead
Contents
1. 0 F 9 A gt q a pa D Block the piston 5 1 Apply wrench to hexagon arrow and unscrew the carrier 1 o E amp z 4 fs amp Free off the oil seal in its seat by tapping it with a suitable tube or a punch Apply puller 1 5910 890 4400 with No 3 1 jaws 0000 893 3706 Clamp the puller arms Pull out the oil seal Take care not to damage the crankshaft stub Clean the sealing face 9 Lubricate sealing lips of new oil seal with grease 9 o A S 5 8 e Fit the installing sleeve 1 4119 893 4600 Apply a thin coating of sealant to the outside diameter of the oil seal E19 Slip the oil seal closed side facing outwards over the installing sleeve Remove the installing sleeve 1 Series 4144 Powerhead Use press sleeve 1 1121 893 2400 to install the oil seal 2 Wait about one minute then rotate the crankshaft several times Install the engine see service manual for Series 4144 Components FS FC KM Tightening torques 3 3 6 3 the Engine The complete engine has to be removed for access to the piston cylinder and crankshaft See service manual for Series 4144 Components FS FC KM Series 4144 Powerhead o o A o lt a fe o Removing and Installing oO Fr 2 a 2 lt ir Q amp 6 4 Removing and Installing t2. o te fe lt a fie o Inspect and clean the sealing face arrow 9 The sealing face must be in perfect condition Always replace components with damaged sealing faces LO 4 3 Always use a new cylinder gasket when re installing the cylinder 938RA036 TG Line up the cylinder gasket 1 so that the tab and cutouts arrows match the contours of the crankcase Place the cylinder gasket 1 in position g u g 8 S Inspect the spacer flange 1 and replace it if necessary even very minor damage can result in engine running problems EJ 4 3 In a new cylinder is installed the spacer flange must be transferred from the old cylinder Series 4144 Powerhead 938RA038 TG Take out the screws arrow together with the connector tag Remove the spacer flange 1 545RA207 TG Remove the gasket 1 always install a new gasket o E gt ise lt a fe gt Inspect and clean the sealing faces arrows and remove any gasket residue 9 Check the sealing faces on the cylinder intake and exhaust ports Series 4144 Powerhead The sealing faces must be in perfect condition If the sealing faces are damaged install a new cylinder or spacer flange Inspect the piston and piston rings and replace if necessary 6 7 938RA040 TG Slide the wooden assembly block 1 1108 893 4800
3. 3 3 Reassemble all other parts in the reverse sequence 6 7 Piston Remove the engine see service manual for Series 4144 Components FS FC KM Remove the cylinder El 6 4 The piston has only one snap ring It is fitted at the carrier side short crankshaft stub 938RA062 TG e Use a suitable tool to grip the hookless snap ring at the recess arrow and ease it out oO Fr 2 amp S lt ir Q amp e Apply assembly drift 1 1130 893 4700 small diameter first to the ignition side of the piston Series 4144 Powerhead a SD Use the assembly drift 2 1130 893 4700 to push the piston pin 1 out of the piston 938RA064 TG If the piston pin is stuck release it by tapping the end of the drift lightly with a hammer Hold the piston steady during this process to ensure that no jolts are transmitted to the connecting rod oO F is lt a ise o Remove the piston 1 from the connecting rod Inspect the piston and replace it if necessary Inspect the piston ring and replace if necessary LJ 6 7 1 Series 4144 Powerhead 938RA066 TG e Check the needle cage 1 and clean it if necessary A new crankshaft must be installed if the needle cage is damaged 9 Lubricate the needle bearing with oil a 938RA067 TG Line up the piston as shown so that the arrow arrow on the piston crown faces
4. arrow faces up oO Fr a 5 lt ir 8 D 938RA013 TG e Position the wrench 1 4130 890 3600 on the crankshaft stub so that its pins engage the recesses arrows 938RA014 TG 1 e E WG n AS 938RA096 TG Tighten down the clutch 1 firmly Tightening torques 3 3 Remove the locking strip from the cylinder Reassemble all other parts in the reverse sequence Series 4144 Powerhead 6 Engine Removal and installation of the engine is described in the service manual for Series 4144 Components FS FC KM 6 1 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 upset the fuel air mixture This makes adjustment of the prescribed idle speed difficult if not impossible Moreover the transition from idle speed to part or full throttle is not smooth Always perform the vacuum test first and then the pressure test The engine can be checked thoroughly for leaks with the pump 0000 850 1300 The engine does not need to be removed for the leakage test Series 4144 Powerhead 6 1 1 Preparations Remove the fan housing see service manual for Series 4144 Components FS FC KM Remove the spark plug boot with cap Unscrew the spark plug 1 Set the piston to top dead center This can be checked through the spark plug hole Fit the s
5. a right hand thread vu WV CG 75 AA Remove the cup spring 1 and washer 2 938RA006 TG Check the individual parts and replace if necessary If the clutch shoes are worn or damaged the entire clutch must be replaced together with the cup spring and washer see parts list Always replace worn or damaged clutch springs in pairs 938RA007 TG e Push the carrier 1 out of the clutch shoes 2 11 938RA008 TG Unhook the springs 1 from the clutch shoes Position the clutch shoes so that the markings arrows are visible Fit new clutch springs oO F D gt lt a oO o Position the carrier 1 so that the word OFF faces up The clutch shoes 2 must be connected by the springs 3 the springs 3 must be properly engaged in the clutch shoes Hold the carrier 1 against one clutch shoe 2 and hold the other clutch shoe at an angle against the carrier 1 pull the shoes slightly apart and push the carrier into position Push the carrier 1 into the clutch shoes 2 as far as stop 12 Installing Push the washer 2 and cup spring 1 onto the crankshaft stub 938RA010 TG 938RA011 TG The cup spring 1 must be properly seated in the carrier arrow and must not slip out of position while the clutch is being screwed home e Fit the clutch so that the word OFF
6. 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 Oil seals in crankcase damaged Crankcase leaking or damaged cracks Replace the oil seals Seal or replace the crankcase Engine does not deliver full power or runs erratically Piston ring worn or broken Muffler spark arresting screen carbonized Air filter dirty Fuel hose kinked or torn Fit new piston ring Clean the muffler inlet and exhaust replace spark arresting screen replace muffler if necessary Replace air filter Fit new hose or position it free from kinks Engine overheating Insufficient cylinder cooling Air inlets in rewind starter blocked or cooling fins on cylinder very dirty Thoroughly clean all cooling air openings and the cylinder fins Series 4144 Powerhead 5 Clutch 5 1 Clutch Drum Troubleshooting 4 1 Remove the engine see service manual for Series 4144 Components FS FC KM 545RA008 TG Pull boot 1 off the spark plug Unscrew the spark plug 1 10 545RA000 TG e Push the locking strip 1 0000 893 5904 into the spark plug hole until it butts against the cylinder wall arrow as shown 938RA001 TG Insert screwdriver bit 1 0812 540 1112 through the clutch drum arrow Loosen t
7. remove any gasket residue LJ 9 The sealing faces must be in perfect condition Always replace components with damaged sealing faces Apply sealant to the groove in the sealing face 9 e S z ir 8 amp The bead of sealant should be about 2 3 mm high a Make sure the sealant does not project into the crankcase Series 4144 Powerhead 938RA054 TG Line up the engine pan so that the lug 2 is on the same side as the crankcase contour arrow Place the engine pan 1 on the sealing face Press the engine pan carefully into position so that the sealant is evenly distributed o b i s irs is lt a ise o Insert the cylinder base screws arrows in the holes to hold the engine pan in position Series 4144 Powerhead 296RA033 TG Prepare the puller 1 5910 890 4400 Fit the No 2 jaws 2 0000 893 3700 Screw the bushing 3 1108 893 4500 onto the puller s spindle Take care not to damage the crankshaft stub o S re gt lt a Q o Apply the puller 1 5910 890 4400 with the jaws under the crankcase ribs arrows and line up the spindle 2 so that the bushing 3 is centered on the engine pan Turn the spindle 2 clockwise until the puller sits tightly Do not overtighten the spindle because the jaws may slip off or damage the crankcase ribs Install the cylinder 6 4 Tightening torqu
8. the spark plug 4 2 Remove the shroud see service manual for Series 4144 Components FS FC KM N S lt a fel amp The electronic breakerless ignition system basically consists of an ignition module 2 and flywheel 1 27 7 1 Ignition Module o N N S lt a e a The ignition module accommodates all the components required to control ignition timing There are two electrical connections on the coil body High voltage output 1 with ignition lead Connector tag 2 for the short circuit wire Testing in the workshop is limited to a spark test A new ignition module must be installed if no ignition spark is obtained after checking that wiring stop switch and flywheel are in good condition 7 1 1 Ignition timing is fixed and cannot be adjusted during repair work Since there is no mechanical wear in these systems ignition timing cannot get out of adjustment during operation 28 7 1 1 Removing and Installing Remove the engine see service manual for Series 4144 Components FS FC KM The air gap between the ignition module and flywheel can be adjusted only when the engine is removed 545RA008 TG 938RA078 TG COR EN g e Disconnect the short circuit wire 1 Take out the screws with washers arrows 938RA080 T The ignition module 1 and ignition lead 2 form a unit Check
9. the crankcase rib 1 and the short crankshaft stub 2 is on the right Place the piston on the connecting rod 938RA068 TG e Push the assembly drift 1 1130 893 4700 small diameter first through the piston and small end needle cage 938RA069 TG Fit the piston pin 2 on the assembly drift 1 and slide it into the piston o e N S lt a oS D N Remove the sleeve 1 5910 893 1708 from the installing tool 2 5910 890 2208 25 533RA128 TG e 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 arrow oO i S lt ia Ss D N e Push the large slotted diameter of the sleeve over the magnet and snap ring The inner pin 2 must point towards the flat face 3 of the tool s shank 26 Press the installing tool downwards into the sleeve until the magnet butts against the end of the guide slot Use a suitable base wooden board u 5 B Remove the sleeve and push it on to the other end of the shank as far as stop The inner pin arrow must again point toward the flat face 938RA070 TG Position the snap ring against the carrier side of the piston Apply the installing tool 5910 890 2208 with the sleeve s taper against the piston boss hold the piston steady center the tool shank exactly and press home until the snap ring slips into
10. the groove Make sure the tool shank is held square on the piston pin axis 938RA071 TG Fit the snap ring 1 so that its gap arrow points down it must not be near the recess 2 Check installed position of snap ring Series 4144 Powerhead 938RA072 TG Inspect the piston ring and replace if necessary W 6 7 1 Install the cylinder 6 4 Remove the engine see service manual for Series 4144 Components FS FC KM Tightening torques 3 3 Reassemble all other parts in the reverse sequence 6 7 1 Piston Ring Remove the piston 6 7 Remove the piston ring from the piston o E o R S lt ina fie D Use a piece of old piston ring to scrape the groove arrows clean Series 4144 Powerhead 938RA074 TG A ay Position the new piston ring in the groove so that the radii arrows at the ring gap face upwards oO F wo N S lt a N e Position the piston ring so that the radii at the ring gap meet at the fixing pin in the piston groove arrow Check correct installed position of the piston ring Install the piston 6 7 7 Ignition System Exercise extreme caution when troubleshooting and carrying out maintenance or repair work on the ignition system The high voltages which occur can cause serious or fatal accidents Troubleshooting on the ignition system should always begin at
11. the sealing plate Tighten down the muffler firmly Reassemble all other parts in the reverse sequence Tightening torques 3 3 6 2 Oil seals It is not necessary to disassemble the engine to replace the oil seals Ignition side Remove the engine see service manual for Series 4144 Components FS FC KM Remove the flywheel 7 5 x a is lt a oO ise a Free off the oil seal in its seat by tapping it with a suitable tube ora punch Apply puller 1 5910 890 4400 with No 3 1 jaws 0000 893 3706 Clamp the puller arms Pull out the oil seal Take care not to damage the crankshaft stub Clean the sealing face 9 Lubricate sealing lips of new oil seal with grease 9 15 F x A S lt ir 2 D Apply a thin coating of sealant to the outside diameter of the oil seal II 9 Carefully push the oil seal open side facing the engine over the crankshaft stub avoid touching the thread so as not to damage the rubber lip Use press sleeve 2 1129 893 2400 to install the oil seal 1 The seating face must be flat and free from burrs Wait about one minute then rotate the crankshaft several times Degrease the crankshaft taper 9 Reassemble all other parts in the reverse sequence 16 Carrier side Remove the engine see service manual for Series 4144 Components FS FC KM
12. 4 Test ignition system with ZAT 3 or ZAT 4 use ZAT 3 as main spark gap see TI 32 94 7 3 33 34 Powerful spark yes Air gap Check ignition module flywheel reset if necessary EJ 7 1 1 Check the flywheel Have pole shoes turned blue Install new flywheel if necessary 7 5 Check short circuit wire Wire damaged Connectors firmly seated Check continuity replace short circuit wire if necessary see service manual for Series 4144 Components FS FC KM Check the ignition lead Severe chafing Spark plug boot Holes cracks Resistance spark plug boot to ground spec 1 5 12kQ Check resistance of ignition lead spec lt 10 Q If necessary install new spark plug boot and or ignition module 7 4 7 1 1 Series 4144 Powerhead Check stop switch on control handle Short circuit wire chafed Operation of stop switch Idle position no connection Position 0 connection Replace short circuit wire if necessary see service manual for Series 4144 Components FS FC KM Powerful spark yes Install new ignition module 7 1 1 Machine runs trouble free no further action necessary Look for fault in fuel system or carburetor Check engine for leaks Check posit
13. Preparing puller 12 Press sleeve 1129 893 2400 Installing oil seals 13 Hook 5910 893 8800 Removing pickup body 14 Press sleeve 1121 893 2400 Installing oil seals 15 Installing sleeve 4119 893 4600 Protects oil seal at starter side No Part Name Part No Application Rem 16 Clamping strap 0000 893 2600 Clamping ring around piston 17 Assembly drift 1130 893 4700 Removing and installing piston pin 18 Wooden assembly block 1108 893 4800 Supporting the piston 19 Installing tool 8 5910 890 2208 Installing hookless snap rings in piston 36 Series 4144 Powerhead No Part Name Part No Application Rem 20 Torque wrench 5910 890 0302 0 5 to 18 Nm No Part Name Part No Application Rem 21 Torque wrench 5910 890 0312 6 to 80 Nm 22 Screwdriver bit T 27 x 125 0812 542 2104 Removing and installing spline socket screws with electric or pneumatic screwdrivers tighten down screws with torque wrench 4 mm 23 Screwdriver bit T 27 x 150 5910 890 2400 IS P screws 4 mm 24 Screwdriver Q SW 8 x 200 5910 890 2420 Hex screws and nuts 1 Remarks 1 Use for releasing only Series 4144 Powerhead 37 9 Servicing Aids No Part Name Part No Application 1 Lubricating grease 225 g tube 0781 120 1111 Oil seals sliding and bearing points 2 STIHL special lubricant 0781 417 1315 Bearing bore in rope rotor rewind spring in starter 3 Press fluid OH 723 0781 957 9000 Rubber elements of A
14. STIHL Contents 1 3 1 3 3 w N gt 6 6 6 7 6 7 1 RA_938_01_01_01 Introduction Safety Precautions Specifications Engine Ignition System Tightening Torquese Troubleshooting Clutch Ignition System Engine Clutch Clutch Drum Clutch Engine Leakage Test Preparations Vacuum Test Pressure Test Oil seals Removing and Installing the Engine Removing and Installing the Cylinder Crankshaft Removing and Installing Bearings Crankshaft Piston Piston Ring Series 4144 Powerhead OND 10 10 11 17 17 21 21 23 27 7 1 7 1 1 7 2 7 3 7 4 7 6 Ignition System Ignition Module Removing and Installing Ignition Timing Testing the Ignition Module Spark Plug Boot Flywheel Ignition System Troubleshooting Special Servicing Tools Servicing Aids 27 28 28 29 30 32 33 36 38 STIHL ANDREAS STIHL AG amp Co KG 2008 1 Introduction This service manual contains detailed descriptions of all the repair and servicing procedures specific to this power tool You should make use of the illustrated parts lists while carrying out repair work They show the installed positions of the individual components and assemblies Refer to the latest edition of the relevant parts list to check the part numbers of any replacement parts A fault on the machine may have several causes To help locate the fault consult th
15. V system 4 STIHL multipurpose grease 0781 120 1109 High voltage output on ignition module 5 Dirko HT red sealant 0783 830 2000 Crankcase oil seals outside 5 Medium strength threadlocking 0786 111 2101 adhesive Loctite 242 6 High strength threadlocking 0786 111 2109 adhesive Loctite 270 7 High strength threadlocking 0786 111 2117 adhesive Loctite 648 8 Standard commercial solvent Cleaning sealing faces and carburetor based degreasant containing no crankshaft stubs and flywheel taper chlorinated or halogenated hydrocarbons 9 Mounting paste 0781 130 1014 Lubrication between crankshaft stub and clutch drum 38 Series 4144 Powerhead Series 4144 Powerhead 39 40 Series 4144 Powerhead
16. and fuels Collect fuel or lubricating oil in a clean container and dispose of it properly in accordance with local environmental regulations Series 4144 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 as well as the safety precautions and warnings in the instruction manual Gasoline is an extremely flammable fuel and can be explosive in certain conditions Always wear suitable protective gloves for operations in which components are heated for assembly or disassembly Improper handling may result in burns or other serious injuries Do not smoke or bring any fire flame or other source of heat near the fuel All work with fuel must be performed outdoors only Spilled fuel must be wiped away immediately Always perform leakage test after working on the fuel system and the engine Series 4144 Powerhead 3 Specifications 3 1 Engine FS 40 FS 50 56 FC 56 KM 56 Displacement 27 2 cm 27 2 cm Bore 34 mm 34 mm Stroke 30 mm 30 mm Engine power to ISO 8893 0 7 kW 1 0 bhp 0 8 kW 1 1 bhp at 8 500 rpm at 8 500 rpm Max permissible speed with cutting attachment 10 000 rpm 10 000 rpm Idle speed 2 800 rpm 2 800 rpm Clutch Centrifugal clutch without Centrifugal clutch without linings linings Clutch engages at 4 200 rpm 4 200 rpm Crankcase leakage test at gauge pressure 0 5 bar
17. ates a vacuum of 0 5 bar If the vacuum reading remains constant or rises to no more than 0 5 bar within 20 seconds it can be assumed that the oil seals are in good condition However if the pressure continues to rise reduced vacuum in the engine the oil seals must be replaced 6 2 After finishing the test push the ring to the right to vent the pump Continue with pressure test 6 1 3 Series 4144 Powerhead 6 1 3 Pressure Test 938RA020 TG Carry out the same preparations as for the vacuum test 6 1 2 Always carry out the vacuum test before the pressure test EI 6 1 2 e Connect pressure hose 1 of pump 0000 850 1300 to nipple arrow g A 8 5 8 Push ring 1 to the right Operate the lever 2 until the pressure gauge arrow indicates a pressure of 0 5 bar If this pressure remains constant for at least 20 seconds the engine is airtight If the pressure drops below 0 5 bar within 20 seconds the leak must be located and the faulty part replaced Series 4144 Powerhead To find the leak coat the suspect area with oil and pressurize the engine Bubbles will appear if a leak exists After finishing the test push the ring to the left to vent the pump disconnect the hose Remove the test flange Install the carburetor see service manual for Series 4144 Components FS FC KM Loosen the muffler and pull out
18. between the piston and crankcase E x lt a 8 D Lubricate the piston piston ring and cylinder wall with oil 9 Use the clamping strap 1 0000 893 2600 to compress the ring around the piston Check correct installed position of ring 6 7 1 Apply the clamping strap 1 so that the piston ring does not project beyond the cylinder wall 296RA046 TG Align the cylinder so that the recess in the cylinder engages the projection on the crankcase arrows Take care not to damage the cylinder gasket oO S x gt lt a ise o While sliding the cylinder over the piston hold the clamping strap tightly around the piston so that the ring does not project it might otherwise break Slide the cylinder over the piston the clamping strap moves downwards at the same time 19 938RA043 TG Remove the clamping strap 1 and wooden assembly block 2 Make sure the cylinder gasket is properly seated o x 3 8 Push the cylinder fully home Insert the screws arrows to hold the cylinder and gasket in position Tighten down the screws in an alternate pattern Remove the puller 20 545RA210 TG Fit the new gasket 1 over the guides arrows on the spacer flange 296RA274 TG e Position the spacer flange 1 with gasket against the cylinder intake port so the guides engage the openings arro
19. e troubleshooting charts for all assemblies and systems in this manual and the STIHL Service Training System Refer to the Technical Information bulletins for engineering changes which have been introduced since publication of this service manual Technical information bulletins also supplement the parts list until a revised edition is issued The special tools mentioned in the descriptions are listed in the chapter on Special Servicing Tools in this manual Use the part numbers to identify the tools in the STIHL Special Tools manual The manual lists all special servicing tools currently available from STIHL Symbols are included in the text and pictures for greater clarity The meanings are as follows In the descriptions e 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 gt Pointer gt Direction of movement 4 2 Reference to another chapter i e chapter 4 2 in this example Service manuals and all technical information bulletins are intended exclusively for the use of properly equipped repair shops They must not be passed to third parties Always use original STIHL replacement parts They can be identified by the STIHL part number the STIHL logo and the STIHL parts symbol 7 This symbol may appear alone on small parts Storing and disposing of oils
20. es 3 3 Remove the puller Clean the crankshaft stubs 9 Install the engine see service manual for Series 4144 Components FS FC KM Reassemble all other parts in the reverse sequence 6 6 Bearings Crankshaft Remove the crankshaft L 6 5 1 Pull off the oil seals 6 5 1 938RA057 TG Pull the ball bearing 1 off the tapered crankshaft stub 23 938RA058 TG Pull the ball bearing 1 off the straight crankshaft stub E D irs is lt a ie a The crankshaft 1 connecting rod 2 and needle bearing form an inseparable unit When fitting a replacement crankshaft always install new ball bearings and oil seals Before installing clean the crankshaft 9 24 938RA060 TG Use a firm base 2 to protect the crankshaft Apply a suitable sleeve 1 to the inner race of the ball bearing at the carrier side and press it home as far as stop o lt a gt Use a firm base 2 to protect the crankshaft e Apply a suitable sleeve 1 to the inner race of the ball bearing at the ignition side and press it home as far as stop Lubricate needle bearings in small end and on crankshaft with oil Install the piston 6 7 Fit new oil seals and install the crankshaft 6 5 1 Install the engine see service manual for Series 4144 Components FS FC KM Tightening torques
21. he Cylinder Before removing the piston decide whether or not the crankshaft clutch or carrier have to be removed as well Cylinder installed To remove the clutch or carrier block the crankshaft by inserting the locking strip in the spark plug hole Cylinder removed To remove the clutch or carrier block the crankshaft by resting the piston on the wooden assembly block 1108 893 4800 938RA029 TG Remove the engine and pull off the carburetor see service manual for Series 4144 Components FS FC KM 938RA030 TG Take out the screws arrows Remove the muffler 1 Remove the ignition module 2 7 1 1 296RA033 TG Prepare the puller 1 5910 890 4400 Fit the No 2 jaws 2 0000 893 3700 Screw the bushing 3 1108 893 4500 onto the puller s spindle 17 938RA031 TG Apply the puller 1 5910 890 4400 with the jaws under the crankcase ribs arrows and line up the spindle 2 so that the bushing 3 is centered on the engine pan Turn the spindle 2 clockwise until the puller sits tightly Do not overtighten the spindle because the jaws may slip off or damage the crankcase ribs g 8 8 5 8 Take out the cylinder screws arrows 18 A i 938RA033 TG e Carefully lift the cylinder 1 away Do not use pointed or sharp edged tools for this job Check the cylinder and replace if necessary 938RA034 TG
22. he crankcase and sealing faces arrows for the engine pan and cylinder clean and remove gasket residue if necessary 9 The sealing faces must be in perfect condition Always replace components with damaged sealing faces 938RA037 TG Check the spacer flange 1 and replace if necessary LQ 6 4 In a new cylinder is installed the spacer flange must be transferred from the old cylinder always install a new gasket 6 4 21 938RA050 TG Fit the installing sleeve 1 4119 893 4600 Push the new oil seals open side facing the ball bearings on to the crankshaft stubs At the ignition side carefully slip the oil seal over the crankshaft stub without touching the thread to avoid damaging the rubber lip g 3 8 8 Position the crankcase 1 so that the bearing seats face up e Before fitting the crankshaft in the crankcase line it up so that the short stub 2 is at the same side as the recesses arrows 22 938RA052 TG Apply thin coating of sealant to outside diameter arrows of the oil seals EI 9 o b o fe is lt a ise o Position the crankshaft connecting rod first in the crankcase Place the crankshaft with bearings and oil seals in the bearing seats making sure the oil seals are firmly against their stops arrows in the crankcase 296RA059 TG Inspect and clean the sealing faces on the engine pan and
23. he screw take care not to damage the screw head Pull off the clutch drum 2 The mounting screw is inside the clutch drum If the screw is damaged the clutch drum must be replaced 165RA029 TG lt 80 Inspect the clutch drum 1 for signs of wear If there are signs of serious wear on the inside diameter of the clutch drum 1 check the remaining wall thickness If it is less than about 80 of the original thickness install a new clutch drum Air Clean away old mounting paste Coat crankshaft stub 1 with mounting paste a about 10 mm 9 Series 4144 Powerhead G oO a Ss S lt ir Q amp Remove the clutch 5 2 e Push clutch drum 1 onto crankshaft stub arrow at ignition side o S z 4 fs amp Coat thread of mounting screw with Loctite LQ 9 Insert screwdriver bit 1 0812 540 1112 through the clutch drum arrow Insert and tighten down the screw firmly take care not to damage the screw head Reassemble all other parts in the reverse sequence Tightening torques 3 3 Series 4144 Powerhead 5 2 Clutch Block the piston 5 1 Remove the clutch drum 5 1 8 5 8 e Position the wrench 1 4130 890 3600 on the crankshaft stub so that its pins engage the recesses arrows 938RA005 TG Unscrew the clutch 1 The clutch has
24. ignition tester 5910 850 4520 Before starting the test install a new spark plug in the cylinder and tighten it down firmly Tightening torques 3 3 Connect spark plug boot to the terminal 2 Attach the ground terminal 1 to the spark plug Use adjusting knob 3 to set the spark gap to about 2 mm o F wo amp 38 While using the ZAT 3 hold it only by the handle 4 or position it in a safe place Keep fingers or other parts of your body at least 1 cm away from the spark window 3 high voltage connection 2 ground connection 5 and the ground terminal 1 High voltage risk of electric shock Crank the engine quickly with the rewind starter 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 the ignition system with the aid of the troubleshooting chart 7 6 Series 4144 Powerhead 7 4 Spark Plug Boot The ignition module 1 and ignition lead 2 form a unit A new ignition module must be installed if the ignition lead is damaged The engine does not need to be removed 938RA087 TG Pull the cap 1 off the spark plug boot 2 Remove the shroud see service manual for Series 4144 Components FS FC KM Pull the boot off the spark plug amp S z d 8 am
25. ion of flywheel on crankshaft 6 1 7 5 Series 4144 Powerhead 35 8 Special Servicing Tools New Special Tools No Part Name Part No Application Rem 1 Test flange 5910 850 4200 Crankcase leakage test 2 Sleeve with 20 chamfer 5910 893 1708 for intstalling tool 8 3 Puller 5910 893 0800 Removing flywheel Existing Special Tools No Part Name Part No Application Rem 1 Locking strip 0000 893 5904 Blocking the piston 2 Carburetor and engine tester 0000 850 1300 Testing engine and carburetor for leaks 3 Puller 5910 890 4501 Removing limiter caps 4 Screwdriver 5910 890 2305 Adjusting carburetor with limiter cap Setting disk 5910 893 6600 Add on for screwdriver adjusting carburetor 5 Screwdriver bit 0812 540 1112 Removing and installing spline socket screws with electric or pneumatic screwdrivers tighten down screws with torque wrench releasing clutch drum 6 Wrench 4130 890 3600 Loosening clutch 7 Hook 5910 890 2800 Detaching springs on clutch shoes 8 Setting gauge 1127 890 6400 Adjusting air gap between the ignition module and flywheel 9 Ignition system tester ZAT 4 5910 850 4503 Testing ignition system 10 Ignition system tester ZAT 3 5910 850 4520 Testing ignition system 11 Puller 5910 890 4400 Removing oil seals Jaws No 3 1 4 0000 893 3706 Removing oil seal s Jaws No 2 0000 893 3700 Holding engine pan on crankcase Threaded bushing 1108 893 4500
26. ncorrect air gap between ignition module and flywheel Flywheel cracked or has other damage or pole shoes have turned blue Ignition timing wrong flywheel out of adjustment key on crankshaft has sheared off Weak magnetization in flywheel Irregular spark Crankcase damaged cracks Press boot firmly onto spark plug and fit new spring if necessary Clean the spark plug or replace if necessary If sooting keeps recurring check air filter Use correct mixture of fuel and oil Set air gap correctly Install new flywheel Locate flywheel properly or install new flywheel Install new flywheel Check operation of switch shaft contact springs and ignition module Faulty insulation or break in ignition lead or short circuit wire Check ignition lead ignition module and replace ignition module if necessary Check operation of spark plug Clean the spark plug or replace if necessary Install new crankcase Series 4144 Powerhead Condition Cause Remedy No spark Spark plug faulty Faulty insulation or short in short circuit wire Break in ignition lead or insulation damaged Ignition module faulty Install new spark plug Check short circuit wire for short circuit to ground Check ignition lead replace ignition module if necessary Install new ignition module Series 4144 Powerhead 4 3 Engine Always check and if necessary repair the following parts before looking for faults
27. p Use suitable pliers to pull the leg spring out of the spark plug boot Unhook the leg spring from the ignition lead Series 4144 Powerhead Pull the boot off the ignition lead 938RA094 TG Remove the protective tube 1 Check for damage and replace if necessary 938RA101 TG Use a pointed tool to pierce the center of the new ignition lead s insulation 100 mm from the end of the lead dimension a Fit the protective tube on the ignition lead 938RA095 TG Pinch the hook of the leg spring into the center of the lead arrow o a is lt a ise a Coat inside of spark plug boot with press fluid 9 Hold the ignition lead and leg spring together and push them into the spark plug boot 31 545RA004 TG Make sure the leg spring arrow locates properly inside the spark plug boot Do not use either graphite grease or silicone insulating paste Reassemble all other parts in the reverse sequence 7 5 Flywheel 545RA000 TG Remove the engine see service manual for Series 4144 Components FS FC KM Unscrew the spark plug Use locking strip 1 to block the piston 5 1 32 938RA090 TG Remove the clutch GQ 5 1 If the flywheel is stuck use a puller o Fr a S lt ir 8 amp Screw the puller 1 5910 893 0800 clockwise on to the crankshaft as far a
28. park plug 1 and tighten it down firmly Tightening torques LQ 3 3 o E v 5 lt a S ha 3 Loosen the screws arrows Lift the muffler 1 938RA016 TG Fit the sealing plate 1 0000 855 8106 between the cylinder exhaust port and muffler and tighten down the screws moderately The sealing plate must completely fill the space between the two screws Remove the carburetor see service manual for Series 4144 Components FS FC KM Check that the gasket 1 is in position 13 The new flange 5910 850 4200 replaces the previous flange 1128 850 4200 The new flange has an additional recess arrow in its sealing face The previous flange 1128 850 4200 can be modified accordingly 296RA009 TG Modify the test flange 1128 850 4200 as shown Fit the test flange 1 5910 850 4200 14 e Fit the nuts arrows and tighten them down firmly 6 1 2 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 counterpressure A test can be carried out with pump 0000 850 1300 to detect this kind of fault a N o E o A 2 ise o e Connect suction hose 1 of pump 0000 850 1300 to nipple arrow 938RA021 TG Push ring 1 to the left Operate the lever 2 until the pressure gauge arrow indic
29. s stop then back it off a 1 4 turn Tap the end of the puller a few times to release the flywheel take care not to damage the crankshaft stub or ball bearing Unscrew the puller and remove the flywheel The flywheel and magnet poles arrows must not be damaged or have turned blue Replace flywheel if necessary Before assembly degrease the bore in the flywheel hub and the crankshaft stub 9 g o z a kd 8 a Make sure the key arrow engages the slot in the crankshaft stub Check the air gap between the ignition module and flywheel and adjust if necessary 7 1 1 Reassemble all other parts in the reverse sequence Tightening torques 3 3 Series 4144 Powerhead 7 6 Ignition System Troubleshooting Troubleshooting can be performed with the engine installed Refer to service manuals of Series 4144 Powerhead or Series 4144 Components FS FC KM for descriptions of procedures Series 4144 Powerhead Engine does not run Knob on carburetor in position I Check the spark plug Smeared with oil black Sooted Electrode gap correct Contacts shorted Clean readjust or replace the plug 7 3 Check the 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 7
30. the ignition module 1 and lead 2 and replace if necessary E z z 4 8 amp Remove the insulator 1 Check the insulator and replace if necessary Check the spark plug boot and replace if necessary W 7 4 Troubleshooting 4 2 Series 4144 Powerhead 938RA082 TG Position the insulator 1 so that the connecting bar 2 points towards the carburetor e Attach the lugs arrows of the insulator 1 to the bosses o F 2 S lt ir 8 Place the ignition module 1 in position so that the ignition lead 2 faces the muffler and insert the screws arrows with washers do not tighten down yet Series 4144 Powerhead 7 FF Push the ignition module 1 back Slide the setting gauge 2 1127 890 6400 between the arms of the ignition module and the flywheel magnet FA 4h 1 aA AS Push the ignition module 1 back the flywheel must turn freely The setting gauge is not shown in the illustration Hold the setting gauge and rotate the flywheel until the magnet poles arrows are next to the ignition module Press the ignition module against the setting gauge Tighten down the screws firmly Tightening torques 3 3 Remove the setting gauge Check operation rotate the flywheel and make sure it does not touch the ignition module 938RA086 TG e Push the boot on to
31. the spark plug Reassemble all other parts in the reverse sequence 7 2 Ignition Timing Ignition timing is fixed and cannot be adjusted during repair work Since there is no mechanical wear in these systems ignition timing cannot get out of adjustment during operation 29 7 3 Testing the Ignition Module 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 Remove the shroud see service manual for Series 4144 Components FS FC KM The following tests are performed on the installed engine 165RA183 TG 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 Tightening torques 3 3 Connect spark plug boot to the input terminal 1 Push the tester s output terminal 3 on to the spark plug High voltage risk of electric shock 30 Crank the engine quickly with the rewind starter 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 the ignition system with the aid of the troubleshooting chart 7 6 o E o S z D N Using the ZAT 3
32. under vacuum 0 5 bar 3 2 Ignition System Air gap between the ignition module and flywheel 0 30 mm Spark plug Suppressed NGK CMR 6 H NGK6H Electrode gap 0 5 mm Series 4144 Powerhead 3 3 Tightening Torquese DG and P Plastoform screws are used in polymer and light metal components These screws form a permanent thread when they are installed for the first time They can be removed and installed as often as necessary without impairing the strength of the screwed assembly providing the specified tightening torque is observed For this reason it is essential to use a torque wrench Fastener Thread size For component Torque Remarks Nm Screw UNC 8 32 Clutch drum crankshaft 3 5 Carrier 3 8 24 Carrier clutch crankshaft 20 0 5 Carrier M 8x1 Carrier starter side crankshaft 17 0 Screw D 5x20 Muffler cylinder 9 0 Screw D 5x20 Spacer flange cylinder 6 0 Screw D 4x20 Ignition module cylinder with washer 45 M 10x1 Spark plug 12 0 Screw D 5x60 Engine pan crankcase cylinder 9 0 Remarks 1 Loctite 242 or 243 medium strength 2 Loctite 270 high strength 3 Loctite 649 high strength 4 Loctite 272 high strength up to 250 C 5 Degrease crankshaft flywheel and mount oil free Use the following procedure when refitting a DG or P screw in an existing thread Place the screw in the hole and rotate it counterclockwise until it drops down slightly Tighten the screw clockwise to the specified torque This procedure ens
33. ures that the screw engages properly in the existing thread and does not form a new thread and weaken the assembly Coat micro encapsulated screws with medium strength Loctite 242 or 243 before reinstalling Power screwdriver setting for polymer DG and P screws max 500 rpm Do not use an impact wrench for releasing or tightening screws Do not mix up screws with and without binding heads Series 4144 Powerhead 4 Troubleshooting 4 1 Clutch Condition Cause Remedy Cutting attachment stops under Clutch shoes badly worn Install new clutch load at full throttle Clutch drum badly worn Install new clutch drum Cutting attachment runs at idle Engine idle speed too high Readjust idle speed screw LA speed Clutch springs stretched or fatigued Replace the clutch springs or install new clutch Clutch spring hooks broken Replace the clutch springs Loud noises Clutch springs stretched or fatigued Replace all clutch springs Clutch shoe retainer broken Install new clutch Clutch shoes and carrier worn Install new clutch 6 Series 4144 Powerhead 4 2 Ignition System Exercise extreme caution while carrying out maintenance and repair work on the ignition system The high voltages which occur can cause serious or fatal accidents Condition Cause Remedy Engine runs roughly misfires temporary loss of power Spark plug boot is loose Spark plug sooted smeared with oil Fuel oil mixture too much oil I
34. ws re C aw ie nn ao 938RA046 TG DM Fit the connector tag 1 Insert screws arrows and tighten them down firmly 545RA055 TG Use a new exhaust gasket Insert the screws e Push the exhaust gasket 1 over the screws K 545RA056 TG Carefully place the muffler 1 in position Fit the screws with washers and check correct position of exhaust gasket again Insert screws and tighten them down firmly Tightening torques 3 3 Install the ignition module 7 1 1 Reassemble all other parts in the reverse sequence Series 4144 Powerhead 6 5 Crankshaft 6 5 1 Removing and Installing Remove the engine see service manual for Series 4144 Components FS FC KM The puller is not necessary for removal of the crankshaft 9 a S 5 8 Block the piston 5 1 Remove the flywheel 2 7 5 Apply wrench to hexagon arrow and unscrew the carrier 1 Remove the cylinder 6 4 Remove the piston 6 7 Series 4144 Powerhead 938RA047 TG Loosen the engine pan 1 at the lug arrow Remove the engine pan 938RA048 TG Release the crankshaft from the bearing seats arrows and take it out of the crankcase Pull the oil seals arrows off the crankshaft stubs Check the crankshaft and ball bearings and replace if necessary LH 6 5 1 296RA053 TG Inspect t
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