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Release 00 - 03/2018

Engine TRE 352

page 33

Service manual

10. ENGINE BLOCK - External repairs

10.4 Overhauling the cylinder head and valves

NOTE - These paragraphs describe all the

operations for checking and overhauling the
cylinder head;

it is left to the operator to assess the advisabi-

lity of performing all the operations described

or only part of them, depending on the type

of engine problems encountered.

1 - Dismount the cylinder head

2 - Move the rocker arms (12); press down the spring

seal cap (17) and move it sideways to remove from

the valve stem (18).

IMPORTANT - The inlet and exhaust valves are diffe-

rent from each other and can be identified by the

marking «IN» (YI - inlet) and «EX» (YE - exhaust), on

the valve head.

3 -

Use an adequate tool to carry out the valve

removal procedure.

4 - Position the tool (19) onto the upper and lower

part of the valve as shown in the figure.

NOTE – The tool must be centered onto the

valve cup and stem part of the valve itself.

5 - Apply pressure with the tool onto the valve cup-

washer (17). The two half-cones (20) will pushed out

of their seat.

12

17

18

17

19

19

20

INDEX

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Summary of Contents for TRE 352

Page 1: ...s or duplication reproduction or translation even partial of the texts in this document may be made without explicit authorization IMPORTANT NOTICE The information contained herein is intended for Service Operations and professionals only able to competently perform the operations described herein using the appropriate equipment in order to safeguard se curity and performance of the machine The ma...

Page 2: ......

Page 3: ...IFICATIONS 9 3 1 Identification 9 3 2 Technical data 9 3 3 Adjustments 9 3 4 Expendable materials 9 3 5 Use limits 9 3 6 Tightening torques 10 3 7 Table of Tightening torques 11 3 8 Identification of engine units 12 4 ENGINE TUNING AND TESTING 13 4 1 Operating guidelines 13 4 2 Engine tuning program 13 4 3 Functional test 14 5 PETROL SUPPLY AND AIR INTAKE 15 5 1 Maintenance of filtering element 16...

Page 4: ...ad 32 10 4 Overhauling the cylinder head and valves 33 10 5 Dismantling and replacing the magneto flywheel 36 10 6 Checking the oil breather 37 10 7 Replacing the upper compression ring of the engine shaft flywheel side 38 10 8 Verify alternator charge 38 10 9 Replacing the lower compression ring of the engine shaft sump side 39 11 ENGINE BLOCK Overhauling internal parts 40 11 1 Remove the engine ...

Page 5: ...s valid B Reference to the chapter and the argument with the relative numbering C Presence of previous or following chapters from the present chapter D Issue date or possible audit E Audit number F Page progressive numbering INTRODUCTION A B C C D E F Certain symbols are used in the manual highlighting particularly important information risks warnings and prescriptions Warns of operations that sho...

Page 6: ...and made available to the manufacturer together with the replaced parts in case clients should make further complaints 1 3 Fault notification The manufacturer should be informed of all faults that recur frequently this allows it to carefully exa mine the problem and make corrections on the production line Similarly the manufacturer shall report any faults traced on its engines indicating the best ...

Page 7: ...ctive damaged or missing guards and covers replace illegible labels do not carry out operations or modifications on the lawnmower or on the engine that could af fect their performance or lead to an improper or different use from the one for which it has been designed and approved warn the customer that the failure to comply with the above points automatically voids the war ranty and the responsibi...

Page 8: ... connectors or cabling clamps Replace those that are damaged 2 Observe the instructions and warnings contained in the present manual and on the safety plates on the engine Inappropriate functioning and maintenance can result in serious injury or even death 3 Ventilation of closed areas In the event that it is necessary to start the engine in a closed environment or if petrol or cleaning oil is bei...

Page 9: ...35 C SAE 30 15W 40 Spark plug RC12YC Champion or equivalent 3 5 Use limits The following table gives the use limits of certain components subject to wear after which the com ponent must be replaced TRE 352 Brushes lenght starter push botton 7 5 11 mm Compression 4 2 bar Minimum inlet valve stem diameter 6 550 mm Minimum exhaust valve stem diameter 6 530 mm Minimum inlet valve head rim thickness 0 ...

Page 10: ... TECHNICAL DATA AND SPECIFICATIONS 3 6 Tightening torques TRE352 336862 10 ME1100004478 100 161860007 II 8 12 Nm 25 32 Nm 8 12 Nm 90 100 Nm 8 10 Nm 8 12 Nm 8 12 Nm 22 26 Nm 11 13 Nm 8 12 Nm 8 12 Nm 35 40 Nm 22 26 Nm 8 12 Nm 8 12 Nm 22 26 Nm 8 12 Nm INDEX BACK ...

Page 11: ...screws 4 6 5 Nm 7 Fixing nuts carburettor and filter 8 12 Nm 7 Fixing screw filter 8 12 Nm 8 Support screws governor assembly 8 12 Nm 9 10 Spark plug tightening torque 25 32 Nm 10 Screws valve cover 8 12 Nm 10 Cylinder head fixing screws M8 22 26 Nm M10 35 40 Nm 10 Screws small plate oil breather 8 12 Nm 10 Fixing screws alternator 8 12 Nm 11 Union screws under carter and sump 22 26 Nm 11 Fixing s...

Page 12: ...ed maintenance operations into different sections each of which refers to an engine component unit as indicated in the diagrams below 3 TECHNICAL DATA AND SPECIFICATIONS TRE352 336862 10 ME1100004478 100 161860007 II Air intake Carburation control Carburettor Ignition Turning off and stopping engine Engine block Starting system INDEX BACK ...

Page 13: ...ccordance with two intervention lines Tuning the engine whenever possible Recommending the client a routine maintenan ce program at set intervals e g at the end of the season or before a long period of inactivity 4 2 Engine tuning program As part of general engine tuning or any intervention on the machine it is recommended that the Service Centre performs a series of operations aimed at maintainin...

Page 14: ... with new petrol check the seal of the tank the cap and the car burettor pipe b Cold starting test With the throttle control in CHOKE start the engine a few times to check it runs normally c Check the engine rpm When the engine is hot enough check the engine speed with the throttle control set to SLO and FAST the readings should be equal to the speci fications 3 2 d Hot start test With the engine ...

Page 15: ...d by gravity and the volume of petrol taken from the tank as the engine runs is compensated by a breather pipe in the cap See the relevant section 14 for advice on resolving problems due to the malfunctioning of the petrol supply system WARNING All interventions on the supply system must be performed in safe conditions therefore do not smoke work in a ventilated environment away from naked flames ...

Page 16: ... air intake system An inefficient filter can let dust or debris enter the cylinder causing premature wear to the piston rings and cylinder The air filter is found on the left hand side of the engine and can be inspected without having to remove other parts 5 PETROL SUPPLY AND AIR INTAKE 2 2 1 3 3 4 5 1 Maintenance of filtering element WARNING Never run the engine without air filter The engine woul...

Page 17: ... prefilter with water and detergent and let it air dry IMPORTANT the prefileter MUST NOT be oiled 6 Refit the prefilter 4 on the cartridge 7 With a jet of compressed air clean inside the seat 5 of the filter by removing dust and remains of grass making sure that the intake pipe hole 6 is closed so that nothing gets inside the pipe 8 Install the foam element 3 in its housing and refit the cover 1 t...

Page 18: ...ning of the star ting system The starting motor is located on the right hand side of the engine For maintenance operations it is neces sary to dismantle the motor from the machine observing the instructions provided in section 11 1 Then proceed with the operations described below 6 STARTING SYSTEM 6 1 Replacement of brushes 1 Remove the screws 1 and lift out the starting motor 2 2 Loosen the screw...

Page 19: ... 11 mm If the length is shorter the brushes must be replaced as indicated below 7 Insert new brushes in the appropriate seats Pay particular attention to the correct positioning of the brushes and springs 8 Re assemble the starter motor securing the screws 3 to the indicated couple 9 Fix the starter button with the screws 1 to the indicated couple 6 2 Replacement of starting motor Perform operatio...

Page 20: ...moke always empty the tank if petrol is not strictly necessary for the operation to be carried out work in a ventilated environment away from naked flames or unprotected sources of heat collect petrol in a suitable container with a cap using a funnel and avoid spilling it on the work bench remove all traces of spilt petrol immediately check you have connected the pipes before pouring petrol back i...

Page 21: ... 8 and the heat guard 9 5 Remove the tie engine shaft 10 of the accele rator throttle lever 6 Remove tie engine shaft 11 of the starter throt tle lever 7 Loosen the central screw 12 fastening the flo at chamber 13 remove the relative gasket 14 and carefully collect all the petrol left in the float chamber 10 9 7 8 INDEX BACK ...

Page 22: ...or following the previous points 9 8 7 in reverse order remembering that It is always advisable to replace the washer 17 and the gasket 14 of the float chamber the float 16 must oscillate freely on the pin 15 the jet 18 should never be modified or replaced with others even if they seem to have the same specifications the choke 21 must open and close regularly the float chamber drain screw 22 must ...

Page 23: ...chieve a stable minimum speed within the above values 7 4 Adjusting maximum speed NOTE This operation is carried out by adju sting the governor system 8 2 7 5 Adjusting the carburation NOTE The carburation is set in the factory and does not normally need changing In the event of irregular functioning clean the carburettor as indicated in section 7 1 Tightening torques 2 Fixing nuts carburettor and...

Page 24: ...e spring that would keep it open the balance between the spring loading and the thrust of the counterweights on the control lever modifies the butterfly opening and adapts the flow of fuel to the engine so that the revolution speed is kept constant with engine load changes See the relevant section 14 for advice on resolving problems related to the governor system 8 1 Adjusting of accelerator cable...

Page 25: ...indicator 6 4 Act on the regulation screw 7 to establish the correct value of the maximum turn system NOTE The engine s maximum speed must be between 2800 100 rpm if you do not read this value proceed as follows 5 Check that the springs are intact that the tie engine shaft 8 is intact and unda maged that the levers are not bent or misshapen and if necessary replace them as a block with their sup p...

Page 26: ...turn pin 12 clockwise to the end of its stroke and then lock the nut 10 8 3 Replacing the lever support 1 Disconnect the accelerator cable 3 and the spring 11 2 Remove the two screws 13 that secure the levers support 14 to the motor 3 Disconnect the tie engine shaft 15 from the starter throttle 4 Perform the above operations in reverse order when assembling 5 Adjust the maximum speed 8 2 Tightenin...

Page 27: ...st 2 Connect the tester 3 to the spark plug cap 4 and to earth on the engine 5 Activate the starter and see in the instrument if the spark jumps 3 If the test has a positive result clean the electro des 2 with compressed air and adjust the distance to 0 6 0 8 mm Remount the spark plug and tighten it to the specified levels Unless otherwise required proceed to verify system components as indicated ...

Page 28: ... any cracks or signs of deterioration or burns which reduce its efficiency and insulation level 5 Loosen the studs 14 securing the coil 12 re lease the brake manually and rotate the flywheel 15 until the magnetic inserts are lined up with the poles of the coil core 6 Insert a 0 35 mm thickness gauge 16 betwe en the flywheel 15 and the coil poles 12 Push the coil until the poles come in contact wit...

Page 29: ...Replacing the coil 1 Remove the cowl and the fan 9 2 2 Disconnect the faston of the earth cable 11 3 Unscrew the studs 14 and remove the coil 12 4 Mount the new coil and regulate the air gap according to the procedure indicated in points 5 and 6 in section 9 2 5 Connect the faston of the earth cable 11 6 Refit the fan and close the nut to the indicated couple and the cowl 9 2 Tightening torques 7 ...

Page 30: ...ect the supply pipe to a compressed air socket with a pressure of approximately 4 2 Bars 60 psi 4 On opening the air tap 4 the manometer gauge on the engine side should position itself in the green zone and remain there for about 30 se conds If the gauge falls rapidly it means that the compression is poor NOTE Lack of compression could be due to incorrect valve clearance 10 2 cylinder head loose o...

Page 31: ... are closed 5 Use a 0 10 mm inlet or a 0 15 mm exhaust feeler gauge 8 to check the gap between the rocker arm and the tip of the valve stem the gauge should pass between without forcing and without a further gap 6 The gap is adjusted by slackening off the nut 9 and suitably adjusting the register nut 10 until the above condition is reached 7 Following adjustment check that the pushrods 11 are prop...

Page 32: ...ur faces 15 4 Carefully clean the inside of the combustion chamber and remove possible deposits from the valve seats 5 Turn the flywheel manually to move the piston and clean inside the cylinder 15 6 When mounting the gasket 16 must always be replaced Remount the cylinder head 14 screwing the seven screws 13 without fully tightening then tighten them to the given torque values using a cross over s...

Page 33: ...ve the rocker arms 12 press down the spring seal cap 17 and move it sideways to remove from the valve stem 18 IMPORTANT The inlet and exhaust valves are diffe rent from each other and can be identified by the marking IN YI inlet and EX YE exhaust on the valve head 3 Use an adequate tool to carry out the valve removal procedure 4 Position the tool 19 onto the upper and lower part of the valve as sh...

Page 34: ... points and replace the valve if it is less than the following even if only in one point 6 550 mm inlet IN YI 6 530 mm exhaust EX YE NOTE The valve seats must be ground by hand using a special grinding tool with an angle of 45 9 Insert the pin 23 in the cylinder head valve guide and then the grinding tool 24 NOTE Grinding must be done taking care to remove as little material as possible 10 Use a c...

Page 35: ... grind the seat and rim of the valve 13 Remove the valve and use clean petrol to carefully clean all traces of paste or metal residues from the valve seat and rim 14 Check the free length of the spring 21 and replace the spring of it is less than 48 50 mm 15 When mounting carefully clean the valve guides and housings of any foreign body apply a film of oil on the valve stems before inser ting them...

Page 36: ...e the correct position of the inlet valve and the exhaust valve marked respectively with YI and YE on the valve head 16 Remount the cylinder head 10 3 and fix the screws to the indicated couple 17 The valve clearances must be checked whe never the cylinder head is removed and refitted 10 2 10 5 Dismantling and replacing the magneto flywheel 1 Remove the cowl 9 2 2 Using a pneumatic wrench unscrew ...

Page 37: ... if it s damaged as semble the Air gap flywheel 28 and the fan 27 Close the nut to the indicated couple 26 and utilize a gun 7 Remount the cowl 9 2 10 6 Checking the oil breather 1 Remove the cowl 9 2 2 Unscrew the three screws 33 fixing the closing plate 34 3 Check that the pad 35 is not damaged or deformed Replace it if necessary If necessary wash with water and neutral deter gents 4 If necessar...

Page 38: ...roximately 44 48 mm taking care not to damage the sealing lip 5 Refit the key 32 10 5 and fix the alternator screws 37 and 39 to the indicated couple 6 Refit the magneto flywheel 10 5 10 8 Verify alternator charge When there isn t a battery charger it s necessary to perform a generator check 1 Remove the magneto flywheel 10 5 2 Disconnect the connectors from the governor and remove the alternator ...

Page 39: ...htening torques 2 Spark plug tightening torque 25 32 Nm 6 Screws valve cover 8 12 Nm 13 Cylinder head fixing screws M8 22 26 Nm M10 35 40 Nm 26 Flywheel fixing nut 90 100 Nm 30 Prigionieri fissaggio bobina 8 12 Nm 33 Screws small plate oil breather 8 12 Nm 37 Fixing screws alternator 8 12 Nm Technical information Compression 4 2 bar Inlet valve clearance 0 10 0 15 mm Exhaust valve clearance 0 15 0...

Page 40: ... four screws anchoring the engine to the machine 4 Hold the engine in points with a firm grip remembering that it weighs approx 24 kg 11 2 Carter opening 1 Position the engine onto a stable support re move the spark plug and collect all the oil present in the sump 2 Turn the engine up side down and position it so that the shaft projects upwards 3 Open the crankcase sump by unscrewing the eight scr...

Page 41: ...s correctly adjusted 8 1 7 Following reassembly it is advisable to check the engine s peak rpm 8 2 11 3 Dismantling and checking the camshaft and counterweight governor 1 Bring the piston to the TDC Top Dead Centre 2 Remove the camshaft 9 3 Measure seat A of the camshaft checking for wear and tear The value must not be lower than 15 916 mm 4 Measure the cams B checking for wear and tear The value ...

Page 42: ...or irregular operation of the centrifugal masses you need to replace the entire unit secured by the support 15 and by the screw 16 9 After the verification reassemble the centrifugal regulator assemble the washer 17 on the inside and insert the pin 14 between the fins of the cen trifugal masses pressing down forcefully so as to block the adjustment system 10 Secure the regulator with the support 1...

Page 43: ... checking and overhauling the thermal components of the engine it is left to the operator to assess the advisability of performing all the operations described or only part of them depending on the type of engine problems encountered 1 Remove the engine from the machine 11 1 2 Remove the cowl 9 2 3 Remove the fan and the flywheel 10 5 4 Dismount the cylinder head 10 3 5 Open the cover 11 2 6 Remov...

Page 44: ...with a feeler gauge 28 the rings must be replaced if the gap is more than 0 60 mm NOTE If a gap of more than 0 6 mm is measu red with new rings it means that the cylinder is worn beyond the acceptable limits and must be replaced The cylinder must be replaced if it shows striping due to a seizure 13 Use a section of an old ring 29 to carefully clean the inside of the piston 25 ring housings ensurin...

Page 45: ... 90 mm even at a single point 17 Check the diameters of the gudgeon pin hou sings A on the piston 25 and replace the piston if they are more than 20 01 mm even at a single point 18 Fit the cap 22 to the connecting rod 23 and check the diameter from the gudgeon pin side and the crank side replace the connecting rod if the values are greater than B 20 02 mm on the gudgeon pin side 11 ENGINE BLOCK Ov...

Page 46: ... To check the alignment between the mani folds and the protruding part of the shaft place the engine shaft on two prismatic guides 34 and with the help of a comparator 35 placed at the end check the displacement by rotating the shaft The shaft must be replaced if the displacement exceeds 0 10 mm IMPORTANT A bent shaft must never be re paired WARNING DANGER A bent shaft causes ab normal vibrations ...

Page 47: ...it Piston marking must point towards the exhaust 23 Put the piston into the ring compression tool 39 24 Oil the inside of the piston liberally and insert the piston with the marking facing the exhaust 25 Mount the engine shaft 33 and the connecting rod cap 22 with the relative screws 24 taking care with the position references 40 so as to avoid inverting the mounting direction of the cap Close the...

Page 48: ...membe ring to replace the washer 6 between the sump and the housing Tightening torques 5 Union screws under carter and sump 22 26 Nm 30 Fixing screws lower connecting rod cap 11 13 Nm Technical information Oil sump capacity 0 8 litri Diameter seat of camshaft 15 916 mm Diameter aspiration cam 32 40 mm Diameter discharge cam 31 90 mm Maximum segments gap in the cylinder 0 60 mm Max compression ring...

Page 49: ...NGINE For maintenance operations relating to this section refer to the manual specific to the machine on which the engine is mounted 13 EXHAUST SYSTEM For maintenance operations relating to this section refer to the manual specific to the machine on which the engine is mounted INDEX BACK ...

Page 50: ...e valve 7 1 or replace the carburettor 7 2 Choke blocked Check and clean the carburettor and the choke 7 1 The spark plug is badly connected or faulty Check spark 9 1 or replace spark plug Blocked air filter Execute the filter cleaning 5 1 Fouling in the combustion chamber Dismount the cylinder head and re move fouling 10 3 Insufficient pressure Check tightness of cylinder head screws replace wash...

Page 51: ...oorly adjusted Adjust the air gap 9 2 and if the problem persists replace the coil 9 3 Oxidation or loosening of spark plug connections Perform spark test 9 1 or repla ce spark plug The engine overreved Governor blocked due to breakage of centrifugal assembly or breakage of external governor springs It is pos sible that the governor is dirty Check the entire governor system 8 and 11 The engine jud...

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