Instruction Manual
Page 2
... AV Spring on Fuel Tank 66 AV Spring on Handlebar 67 Stop Buffers 68 Buffers on Machines with Manual Fuel Pump 85 12.5 Carburetor 88 12.5.1 Leakage Test 89 RA_737_00_01_01 MS 231, MS 231 C, MS 251, MS 251 C q © ANDREAS STIHL AG & Co. Fuel System 81 12.1 Air Filter 81 12.2 Baffle 81 12.3 Filter Base 81 12...
... AV Spring on Fuel Tank 66 AV Spring on Handlebar 67 Stop Buffers 68 Buffers on Machines with Manual Fuel Pump 85 12.5 Carburetor 88 12.5.1 Leakage Test 89 RA_737_00_01_01 MS 231, MS 231 C, MS 251, MS 251 C q © ANDREAS STIHL AG & Co. Fuel System 81 12.1 Air Filter 81 12.2 Baffle 81 12.3 Filter Base 81 12...
Instruction Manual
Page 3
Servicing Aids 112 2 MS 231, MS 231 C, MS 251, MS 251 C Manual Fuel Pump 105 12.11.4 Manual Fuel Pump 107 12.11.5 Tank Housing 108 13. Special Servicing Tools 110 14. Contents 12.6 Servicing the Carburetor 90 12.6.1 Metering Diaphragm 90 12.6.2 ...
Servicing Aids 112 2 MS 231, MS 231 C, MS 251, MS 251 C Manual Fuel Pump 105 12.11.4 Manual Fuel Pump 107 12.11.5 Tank Housing 108 13. Special Servicing Tools 110 14. Contents 12.6 Servicing the Carburetor 90 12.6.1 Metering Diaphragm 90 12.6.2 ...
Instruction Manual
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... the individual components and assemblies. The meanings are listed in the chapter on "Troubleshooting" and the "STIHL Service Training System" for greater clarity. MS 231, MS 231 C, MS 251, MS 251 C 3 Introduction and Safety Precautions 2710RA320 TG 1.1 Introduction This service manual contains detailed descriptions of all assemblies. Engage the bar mounting stud in the outer bore in the...
... the individual components and assemblies. The meanings are listed in the chapter on "Troubleshooting" and the "STIHL Service Training System" for greater clarity. MS 231, MS 231 C, MS 251, MS 251 C 3 Introduction and Safety Precautions 2710RA320 TG 1.1 Introduction This service manual contains detailed descriptions of all assemblies. Engage the bar mounting stud in the outer bore in the...
Instruction Manual
Page 5
...explosive in this service manual. Other press fluids are heated for operations in all local and countryspecific safety regulations as well as necessary. They can be overstretched during removal. All work with the aid of repairs or maintenance work on to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C Always install new...lubricating oil in a clean container and dispose of it properly in accordance with the shroud mounted in the course of STIHL press fluid, b 14. Improper handling may appear alone on the fuel system and the engine. Do not cut open fuel hoses ...
...explosive in this service manual. Other press fluids are heated for operations in all local and countryspecific safety regulations as well as necessary. They can be overstretched during removal. All work with the aid of repairs or maintenance work on to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C Always install new...lubricating oil in a clean container and dispose of it properly in accordance with the shroud mounted in the course of STIHL press fluid, b 14. Improper handling may appear alone on the fuel system and the engine. Do not cut open fuel hoses ...
Instruction Manual
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... mm 30.0 mm 2.0 kW (2.7 bhp) at 9,500 rpm 13,000 rpm 2,800 rpm Centrifugal clutch without linings 3,500 rpm 0.5 bar 0.5 bar MS 251 45.6 cm3 44.0 mm 30.0 mm 2.2 kW (3.0 bhp) at 9,500 rpm 13,000 rpm 2,800 rpm Centrifugal clutch without linings 3,500 rpm Carburetor... pressure: Fuel: 0.8 bar 0.5 bar as specified in instruction manual Air gap between ignition module and fanwheel: Spark plug (resistor type): Electrode gap: 0.30 (+ 0.05/- 0.10) mm NGK CMR 6 H 0.5 mm Speed-controlled Ematic oil pump Oil delivery rate: 8.0 (+/3.0) cm3/min at 10,000 rpm MS 231, MS 231 C, MS 251, MS 251 C 5
... mm 30.0 mm 2.0 kW (2.7 bhp) at 9,500 rpm 13,000 rpm 2,800 rpm Centrifugal clutch without linings 3,500 rpm 0.5 bar 0.5 bar MS 251 45.6 cm3 44.0 mm 30.0 mm 2.2 kW (3.0 bhp) at 9,500 rpm 13,000 rpm 2,800 rpm Centrifugal clutch without linings 3,500 rpm Carburetor... pressure: Fuel: 0.8 bar 0.5 bar as specified in instruction manual Air gap between ignition module and fanwheel: Spark plug (resistor type): Electrode gap: 0.30 (+ 0.05/- 0.10) mm NGK CMR 6 H 0.5 mm Speed-controlled Ematic oil pump Oil delivery rate: 8.0 (+/3.0) cm3/min at 10,000 rpm MS 231, MS 231 C, MS 251, MS 251 C 5
Instruction Manual
Page 20
... strip (1) 0000 893 5904 so that the raised hexagon (arrow) faces outwards. : Fit the clutch (2) and tighten it down firmly - MS 231, MS 231 C, MS 251, MS 251 C 19 Remove and install the clutch drum, see instruction manual. - Inspect the clutch drum (1) for signs of the original thickness, install a new clutch drum. - as shown in the reverse...
... strip (1) 0000 893 5904 so that the raised hexagon (arrow) faces outwards. : Fit the clutch (2) and tighten it down firmly - MS 231, MS 231 C, MS 251, MS 251 C 19 Remove and install the clutch drum, see instruction manual. - Inspect the clutch drum (1) for signs of the original thickness, install a new clutch drum. - as shown in the reverse...
Instruction Manual
Page 21
...) - The clutch drum must come to a complete standstill. Install a new brake band if there are noticeable signs of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C Remove the clutch drum, b 4.1 - With the chain brake activated (locked), open the throttle wide and let go of the most ...(1) from the brake lever (2). 2310RA008 TG 2310RA006 TG - With the chain brake released, open the throttle wide and activate the brake manually - the chain must rotate freely when the lockout lever is depressed. The braking time is imperceptible to one of the lockout lever on...
...) - The clutch drum must come to a complete standstill. Install a new brake band if there are noticeable signs of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C Remove the clutch drum, b 4.1 - With the chain brake activated (locked), open the throttle wide and let go of the most ...(1) from the brake lever (2). 2310RA008 TG 2310RA006 TG - With the chain brake released, open the throttle wide and activate the brake manually - the chain must rotate freely when the lockout lever is depressed. The braking time is imperceptible to one of the lockout lever on...
Instruction Manual
Page 29
... fuel hose (3) or, on versions with a manual fuel pump, to the right of the fuel hose (3) and fuel return hose (2). : Push the brake cable (1), short hook (4) first, through the bore (arrow) in the engine housing. 1 2 : Push the insert (1) with the housing ribs. 28 MS 231, MS 231 C, MS 251, MS 251 C Disassembling the brake cable and retainer...
... fuel hose (3) or, on versions with a manual fuel pump, to the right of the fuel hose (3) and fuel return hose (2). : Push the brake cable (1), short hook (4) first, through the bore (arrow) in the engine housing. 1 2 : Push the insert (1) with the housing ribs. 28 MS 231, MS 231 C, MS 251, MS 251 C Disassembling the brake cable and retainer...
Instruction Manual
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... check and, if necessary, repair the fuel system, carburetor, air filter and ignition system before looking for faults on the cylinder. 32 MS 231, MS 231 C, MS 251, MS 251 C make sure there is no dirt falls into the cylinder. - take care not to push home the new plugs squarely and uniformly ... Before removing the muffler, set the piston to top dead center to line it up on the engine. - Remove any gasket residue - see instruction manual. do not re-use plugs that the tabs (arrows) point towards the cylinder. : Fit the new exhaust gasket (1) and use the tabs (arrows)...
... check and, if necessary, repair the fuel system, carburetor, air filter and ignition system before looking for faults on the cylinder. 32 MS 231, MS 231 C, MS 251, MS 251 C make sure there is no dirt falls into the cylinder. - take care not to push home the new plugs squarely and uniformly ... Before removing the muffler, set the piston to top dead center to line it up on the engine. - Remove any gasket residue - see instruction manual. do not re-use plugs that the tabs (arrows) point towards the cylinder. : Fit the new exhaust gasket (1) and use the tabs (arrows)...
Instruction Manual
Page 72
... TG - Reassemble all other parts in the instruction manual. 10. short circuit wire's terminal sleeve must touch the contact spring (arrow) in the carburetor box. - Installing 1 10.1.1 Removing and Installing - Remove the contact spring, b 7.7.4 1 2310RA162 TG 2 : Position the switch lever (1) in position "0". - MS 231, MS 231 C, MS 251, MS 251 C 71 Remove the air filter, b 12.1 - Pull...
... TG - Reassemble all other parts in the instruction manual. 10. short circuit wire's terminal sleeve must touch the contact spring (arrow) in the carburetor box. - Installing 1 10.1.1 Removing and Installing - Remove the contact spring, b 7.7.4 1 2310RA162 TG 2 : Position the switch lever (1) in position "0". - MS 231, MS 231 C, MS 251, MS 251 C 71 Remove the air filter, b 12.1 - Pull...
Instruction Manual
Page 78
... TG : Carefully pull the carburetor (1) off the studs - Check operation - Check the throttle rod and replace if necessary Installing 2 : Push the carburetor (1) with manual fuel pump 1 - MS 231, MS 231 C, MS 251, MS 251 C 77 Install the filter base, b 12.3 - take care not to overstretch the fuel hose (2). - Install the throttle trigger, b 10.2 1 1 2310RA294 TG 2310RA297 TG...
... TG : Carefully pull the carburetor (1) off the studs - Check operation - Check the throttle rod and replace if necessary Installing 2 : Push the carburetor (1) with manual fuel pump 1 - MS 231, MS 231 C, MS 251, MS 251 C 77 Install the filter base, b 12.3 - take care not to overstretch the fuel hose (2). - Install the throttle trigger, b 10.2 1 1 2310RA294 TG 2310RA297 TG...
Instruction Manual
Page 82
... ground wire (2) out of the buffer (2). - See also Troubleshooting, b 3.6, b 3.7 1 - Remove the contact spring, b 7.7.4 - Remove the switch shaft, b 10.1 - 2310RA198 TG 12. see instruction manual. - Remove the choke rod, b 10.3.3 - Fuel System 12.1 Air Filter 12.2 Baffle Dirty air filters reduce engine power, increase fuel consumption and make starting more.... - Remove the shroud, b 6.4 1 : Pull the filter base (1) off the studs (arrows). 2310RA313 TG 1 : Unscrew the nuts (arrows). 1 : Remove the baffle (1). 2310RA312 TG - MS 231, MS 231 C, MS 251, MS 251 C 81
... ground wire (2) out of the buffer (2). - See also Troubleshooting, b 3.6, b 3.7 1 - Remove the contact spring, b 7.7.4 - Remove the switch shaft, b 10.1 - 2310RA198 TG 12. see instruction manual. - Remove the choke rod, b 10.3.3 - Fuel System 12.1 Air Filter 12.2 Baffle Dirty air filters reduce engine power, increase fuel consumption and make starting more.... - Remove the shroud, b 6.4 1 : Pull the filter base (1) off the studs (arrows). 2310RA313 TG 1 : Unscrew the nuts (arrows). 1 : Remove the baffle (1). 2310RA312 TG - MS 231, MS 231 C, MS 251, MS 251 C 81
Instruction Manual
Page 86
... (1). : Remove the connector (2) and disconnect it to one side with Manual Fuel 2 Pump 1 - Remove the throttle rod, b 10.3.4 : Pull the fuel return hose (1) out of the cylinder and pull the air guide shroud away at the same time. 2310RA338 TG MS 231, MS 231 C, MS 251, MS 251 C 85 Remove the carburetor, b 12.5 - Models with the wiring...
... (1). : Remove the connector (2) and disconnect it to one side with Manual Fuel 2 Pump 1 - Remove the throttle rod, b 10.3.4 : Pull the fuel return hose (1) out of the cylinder and pull the air guide shroud away at the same time. 2310RA338 TG MS 231, MS 231 C, MS 251, MS 251 C 85 Remove the carburetor, b 12.5 - Models with the wiring...
Instruction Manual
Page 89
... is in the reverse sequence. 2310RA351 TG Models with manual fuel pump - Check the carburetor and service or replace if necessary. - Install a new fuel hose, b 12.11.2 2310RA353 TG 88 MS 231, MS 231 C, MS 251, MS 251 C Open the fuel tank cap and drain the fuel ... place. - 2310RA286 TG 2 1 3 1 2310RA350 TG : Push the rubber grommet (1) into the guides (arrows) - All models 1 - Install filter base with manual fuel pump 1 - Install new fuel intake hose, b 12.11.3 Installing 1 Make sure the washer (1) is open. : Remove the carburetor (1). Models with wiring ...
... is in the reverse sequence. 2310RA351 TG Models with manual fuel pump - Check the carburetor and service or replace if necessary. - Install a new fuel hose, b 12.11.2 2310RA353 TG 88 MS 231, MS 231 C, MS 251, MS 251 C Open the fuel tank cap and drain the fuel ... place. - 2310RA286 TG 2 1 3 1 2310RA350 TG : Push the rubber grommet (1) into the guides (arrows) - All models 1 - Install filter base with manual fuel pump 1 - Install new fuel intake hose, b 12.11.3 Installing 1 Make sure the washer (1) is open. : Remove the carburetor (1). Models with wiring ...
Instruction Manual
Page 90
...parts in the - Metering diaphragm or gasket damaged, replace if necessary, b 12.6.1 1 2. Test the tank vent if necessary, b 12.10.1 - MS 231, MS 231 C, MS 251, MS 251 C 89 Install the filter base, b 12.3 - After completing the test, push the ring (1) to the left to the nipple (2) 0000 855 9200.... : Push the fuel hose with manual fuel pump 1 : Push the new fuel hose (1) onto the nipples (arrows). 2310RA356 TG 2310RA355...
...parts in the - Metering diaphragm or gasket damaged, replace if necessary, b 12.6.1 1 2. Test the tank vent if necessary, b 12.10.1 - MS 231, MS 231 C, MS 251, MS 251 C 89 Install the filter base, b 12.3 - After completing the test, push the ring (1) to the left to the nipple (2) 0000 855 9200.... : Push the fuel hose with manual fuel pump 1 : Push the new fuel hose (1) onto the nipples (arrows). 2310RA356 TG 2310RA355...
Instruction Manual
Page 91
...b 3.6 - If the gasket and diaphragm are stuck to be replaced. - Reassemble all other parts in the tabs. 90 MS 231, MS 231 C, MS 251, MS 251 C The diaphragm material is subjected to damage the Oring (arrow). - Check the metering diaphragm for signs of the choke shutter... end cover (1). Remove the metering diaphragm, b 12.6.1 2310RA257 TG 2310RA259 TG 1 : Check the O-ring (1) and replace it if necessary : On versions with a manual fuel pump, check the nipple (2) and replace the end cover if necessary. - Install a new gasket. Installing 1 2 : Position the end cover (1) so that ...
...b 3.6 - If the gasket and diaphragm are stuck to be replaced. - Reassemble all other parts in the tabs. 90 MS 231, MS 231 C, MS 251, MS 251 C The diaphragm material is subjected to damage the Oring (arrow). - Check the metering diaphragm for signs of the choke shutter... end cover (1). Remove the metering diaphragm, b 12.6.1 2310RA257 TG 2310RA259 TG 1 : Check the O-ring (1) and replace it if necessary : On versions with a manual fuel pump, check the nipple (2) and replace the end cover if necessary. - Install a new gasket. Installing 1 2 : Position the end cover (1) so that ...
Instruction Manual
Page 99
... snaps into position. - Always replace components with manual fuel pump, b 12.4.1 : Inspect and clean the sealing faces (arrows), b 14 The sealing faces must be clear, clean if necessary - a dirty bore can cause engine running problems, b 3.7 1 2310RA292 TG 2310RA358 TG A damaged intake manifold can result in the reverse sequence. 98 MS 231, MS 231 C, MS 251, MS 251 C
... snaps into position. - Always replace components with manual fuel pump, b 12.4.1 : Inspect and clean the sealing faces (arrows), b 14 The sealing faces must be clear, clean if necessary - a dirty bore can cause engine running problems, b 3.7 1 2310RA292 TG 2310RA358 TG A damaged intake manifold can result in the reverse sequence. 98 MS 231, MS 231 C, MS 251, MS 251 C
Instruction Manual
Page 100
... fuel tank cap and drain the fuel tank, b 1. - Reassemble all other parts in the fuel tank. Remove the carburetor, b 12.5 MS 231, MS 231 C, MS 251, MS 251 C 99 Install the air guide shroud, b 12.4 Models with manual fuel pump 1 2 : Use a suitable plug (2) to seal the fuel suction hose (1). 2310RA362 TG 1 : Push the ring (1) to the left...
... fuel tank cap and drain the fuel tank, b 1. - Reassemble all other parts in the fuel tank. Remove the carburetor, b 12.5 MS 231, MS 231 C, MS 251, MS 251 C 99 Install the air guide shroud, b 12.4 Models with manual fuel pump 1 2 : Use a suitable plug (2) to seal the fuel suction hose (1). 2310RA362 TG 1 : Push the ring (1) to the left...
Instruction Manual
Page 102
... tank if necessary. - Pour a small amount of dirt. Remove the pickup body, b 11.1 - Dispose of the filter eventually become clogged with manual fuel pump, b 12.4.1 2310RA374 TG MS 231, MS 231 C, MS 251, MS 251 C 101 The fine pores of fuel properly in the reverse sequence. : Take out the screw (1). 1 2310RA371 TG 12.11 Fuel Intake 12...
... tank if necessary. - Pour a small amount of dirt. Remove the pickup body, b 11.1 - Dispose of the filter eventually become clogged with manual fuel pump, b 12.4.1 2310RA374 TG MS 231, MS 231 C, MS 251, MS 251 C 101 The fine pores of fuel properly in the reverse sequence. : Take out the screw (1). 1 2310RA371 TG 12.11 Fuel Intake 12...
Instruction Manual
Page 105
... (arrow). : Lift the tank housing (2). - Insert the screws and tighten them down the screw (2) firmly. - Insert screw and tighten it in the reverse sequence. 104 MS 231, MS 231 C, MS 251, MS 251 C Do not overstretch the fuel suction hose. - Close the tank cap. - Machines with manual fuel pump, b 12.4.1 - Fit the pickup body, b 12.11.1 2 2 1 1 -
... (arrow). : Lift the tank housing (2). - Insert the screws and tighten them down the screw (2) firmly. - Insert screw and tighten it in the reverse sequence. 104 MS 231, MS 231 C, MS 251, MS 251 C Do not overstretch the fuel suction hose. - Close the tank cap. - Machines with manual fuel pump, b 12.4.1 - Fit the pickup body, b 12.11.1 2 2 1 1 -