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. Chain Lubrication 78 11.1 Pickup Body 78 11.2 Oil Suction Hose 78 11.3 Oil Pump...
... 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. Chain Lubrication 78 11.1 Pickup Body 78 11.2 Oil Suction Hose 78 11.3 Oil Pump...
Instruction Manual
Page 3
... 100 12.11 Fuel Intake 101 12.11.1 Pickup Body 101 12.11.2 Fuel Hose 101 12.11.3 Fuel Hoses - Special Servicing Tools 110 14. Manual Fuel Pump 105 12.11.4 Manual Fuel Pump 107 12.11.5 Tank Housing 108 13. Servicing Aids 112 2 MS 231, MS 231 C, MS 251, MS 251 C
... 100 12.11 Fuel Intake 101 12.11.1 Pickup Body 101 12.11.2 Fuel Hose 101 12.11.3 Fuel Hoses - Special Servicing Tools 110 14. Manual Fuel Pump 105 12.11.4 Manual Fuel Pump 107 12.11.5 Tank Housing 108 13. Servicing Aids 112 2 MS 231, MS 231 C, MS 251, MS 251 C
Instruction Manual
Page 4
... plate by the screw heads on "Special Servicing Tools" in the "STIHL Special Tools" manual. They must not project since they, depending on the machine may damage housings when the machine is clamped in the illustration above the text - MS 231, MS 231 C, MS 251, MS 251 C 3 Action to the assembly stand with the M 8 nut (arrow). 2310RA000 TG...
... plate by the screw heads on "Special Servicing Tools" in the "STIHL Special Tools" manual. They must not project since they, depending on the machine may damage housings when the machine is clamped in the illustration above the text - MS 231, MS 231 C, MS 251, MS 251 C 3 Action to the assembly stand with the M 8 nut (arrow). 2310RA000 TG...
Instruction Manual
Page 5
... assembly or disassembly. replace as the safety precautions and warnings in this service manual. The specifications must be explosive in accordance with the aid of heat near the...serious injuries. Always install new hoses - They can be tightened to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C Exercise extreme caution while carrying out maintenance and repair work with fuel must be...an extremely flammable fuel and can cause serious or fatal accidents. do not use original STIHL replacement parts. there is otherwise a risk of injury from the fanwheel and a risk ...
... assembly or disassembly. replace as the safety precautions and warnings in this service manual. The specifications must be explosive in accordance with the aid of heat near the...serious injuries. Always install new hoses - They can be tightened to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C Exercise extreme caution while carrying out maintenance and repair work with fuel must be...an extremely flammable fuel and can cause serious or fatal accidents. do not use original STIHL replacement parts. there is otherwise a risk of injury from the fanwheel and a risk ...
Instruction Manual
Page 6
... 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...gauge 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...gauge 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
... - left-hand thread. - 4. Remove and install the clutch drum, see instruction manual. - If there are signs of serious wear on the piston crown - Remove the locking strip from the cylinder. - Reassemble all other parts in the illustration. MS 231, MS 231 C, MS 251, MS 251 C 19 Install the clutch drum. : Hold the locking strip (1) 0000 893 5904...
... - left-hand thread. - 4. Remove and install the clutch drum, see instruction manual. - If there are signs of serious wear on the piston crown - Remove the locking strip from the cylinder. - Reassemble all other parts in the illustration. MS 231, MS 231 C, MS 251, MS 251 C 19 Install the clutch drum. : Hold the locking strip (1) 0000 893 5904...
Instruction Manual
Page 21
.... Remove the clutch drum, b 4.1 - With the chain brake activated (locked), open the throttle wide and activate the brake manually - to the eye. The braking time is in terms of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C A fatigued or stretched brake spring has the same negative effect. 5.2 Brake Band - Starting the engine 2 1 - Engage the...
.... Remove the clutch drum, b 4.1 - With the chain brake activated (locked), open the throttle wide and activate the brake manually - to the eye. The braking time is in terms of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C A fatigued or stretched brake spring has the same negative effect. 5.2 Brake Band - Starting the engine 2 1 - Engage the...
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 The insert must be flush with...
... 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 The insert must be flush with...
Instruction Manual
Page 33
...Remove the shroud, b 6.4 Before removing the muffler, set the piston to top dead center to line it up on the engine. - see instruction manual. Installing - make sure there is no dirt falls into the cylinder. - Position the new exhaust gasket (1) so that no gasket residue or dirt ... 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 Use a blunt tool to damage the plugs. Remove the exhaust gasket - Remove any gasket residue - Cover the exhaust port.
...Remove the shroud, b 6.4 Before removing the muffler, set the piston to top dead center to line it up on the engine. - see instruction manual. Installing - make sure there is no dirt falls into the cylinder. - Position the new exhaust gasket (1) so that no gasket residue or dirt ... 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 Use a blunt tool to damage the plugs. Remove the exhaust gasket - Remove any gasket residue - Cover the exhaust port.
Instruction Manual
Page 72
..., b 12.3 : Push the switch lever (1) onto the filter base's shaft (2) as far as stop . - MS 231, MS 231 C, MS 251, MS 251 C 71 10. Remove the air filter, b 12.1 - Fit the contact spring, b 7.7.4 2310RA164 TG - Reassemble all other parts in the instruction manual. Check the filter base and replace 2 The positions of the Master Control it and...
..., b 12.3 : Push the switch lever (1) onto the filter base's shaft (2) as far as stop . - MS 231, MS 231 C, MS 251, MS 251 C 71 10. Remove the air filter, b 12.1 - Fit the contact spring, b 7.7.4 2310RA164 TG - Reassemble all other parts in the instruction manual. Check the filter base and replace 2 The positions of the Master Control it and...
Instruction Manual
Page 78
... hose (2) over the studs - Reassemble all other parts in the reverse sequence. Check the throttle rod and replace if necessary Installing 2 : Push the carburetor (1) with manual fuel pump 1 2310RA200 TG 2 1 2310RA295 TG 2310RA298 TG : Carefully pull the carburetor (1) off the studs - Check operation - All models 1 : Pass the throttle cable (1) through ... tank and engine housings and through the opening (arrow) in the direction of the rear handle. 1 2 : Fit the new fuel hose (1). Put the carburetor with manual fuel pump 1 - All models - MS 231, MS 231 C, MS 251, MS 251 C 77
... hose (2) over the studs - Reassemble all other parts in the reverse sequence. Check the throttle rod and replace if necessary Installing 2 : Push the carburetor (1) with manual fuel pump 1 2310RA200 TG 2 1 2310RA295 TG 2310RA298 TG : Carefully pull the carburetor (1) off the studs - Check operation - All models 1 : Pass the throttle cable (1) through ... tank and engine housings and through the opening (arrow) in the direction of the rear handle. 1 2 : Fit the new fuel hose (1). Put the carburetor with manual fuel pump 1 - All models - MS 231, MS 231 C, MS 251, MS 251 C 77
Instruction Manual
Page 82
... the filter base (1) out of the buffer (2). 2310RA195 TG : Pull the short circuit wire (1) and ground wire (2) out of engine power. - MS 231, MS 231 C, MS 251, MS 251 C 81 Check the air filter and clean or replace if necessary - Remove the air filter, b 12.1 2 : Pull the filter base (1) out...Filter 12.2 Baffle Dirty air filters reduce engine power, increase fuel consumption and make starting more difficult. see instruction manual. - Reassemble in the reverse sequence. - Reassemble in the reverse sequence. 12.3 Filter Base - Remove the contact spring, b 7.7.4 - Remove the switch shaft,...
... the filter base (1) out of the buffer (2). 2310RA195 TG : Pull the short circuit wire (1) and ground wire (2) out of engine power. - MS 231, MS 231 C, MS 251, MS 251 C 81 Check the air filter and clean or replace if necessary - Remove the air filter, b 12.1 2 : Pull the filter base (1) out...Filter 12.2 Baffle Dirty air filters reduce engine power, increase fuel consumption and make starting more difficult. see instruction manual. - Reassemble in the reverse sequence. - Reassemble in the reverse sequence. 12.3 Filter Base - Remove the contact spring, b 7.7.4 - Remove the switch shaft,...
Instruction Manual
Page 86
... : Pull the wiring harness and rubber grommet (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 Put the wiring harness with the wiring harness still attached, b 12.3 - Pull the filter base off the spark plug. : Take out the screw...
... : Pull the wiring harness and rubber grommet (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 Put the wiring harness with the wiring harness still attached, b 12.3 - Pull the filter base off the spark plug. : Take out the screw...
Instruction Manual
Page 89
..., b 12.3 - Stub (3) must engage bore in the reverse sequence. 2310RA351 TG Models with manual fuel pump - Install a new fuel hose, b 12.11.2 2310RA353 TG 88 MS 231, MS 231 C, MS 251, MS 251 C Collect the fuel in place. Check the components and replace as necessary. 2310RA352 TG Disconnect the... - Open the fuel tank cap and drain the fuel tank. position short circuit wire under the ground wire. 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 in place. 1 2 2310RA199 TG 12...
..., b 12.3 - Stub (3) must engage bore in the reverse sequence. 2310RA351 TG Models with manual fuel pump - Install a new fuel hose, b 12.11.2 2310RA353 TG 88 MS 231, MS 231 C, MS 251, MS 251 C Collect the fuel in place. Check the components and replace as necessary. 2310RA352 TG Disconnect the... - Open the fuel tank cap and drain the fuel tank. position short circuit wire under the ground wire. 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 in place. 1 2 2310RA199 TG 12...
Instruction Manual
Page 90
... After completing the test, push the ring (1) to the left to full throttle position, the throttle shutter must be tested for leaks with manual fuel pump 1 : Push the new fuel hose (1) onto the nipples (arrows). 2310RA356 TG 2310RA355 TG 2310RA354 TG 2310RA255 TG - Check... trigger to vent the system and then pull the fuel hose off the carburetor. - Reassemble all other parts in the reverse sequence. MS 231, MS 231 C, MS 251, MS 251 C 89 The inlet needle is airtight. Push the carburetor fully home. Metering diaphragm or gasket damaged, replace if necessary, b 12...
... After completing the test, push the ring (1) to the left to full throttle position, the throttle shutter must be tested for leaks with manual fuel pump 1 : Push the new fuel hose (1) onto the nipples (arrows). 2310RA356 TG 2310RA355 TG 2310RA354 TG 2310RA255 TG - Check... trigger to vent the system and then pull the fuel hose off the carburetor. - Reassemble all other parts in the reverse sequence. MS 231, MS 231 C, MS 251, MS 251 C 89 The inlet needle is airtight. Push the carburetor fully home. Metering diaphragm or gasket damaged, replace if necessary, b 12...
Instruction Manual
Page 91
...diaphragm (2) and gasket (1). : Position the gasket (1) and metering diaphragm (2) so that the stub (3) points in the tabs. 90 MS 231, MS 231 C, MS 251, MS 251 C Note installed positions of metering diaphragm and gasket, then tighten down yet. - 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 ...
...diaphragm (2) and gasket (1). : Position the gasket (1) and metering diaphragm (2) so that the stub (3) points in the tabs. 90 MS 231, MS 231 C, MS 251, MS 251 C Note installed positions of metering diaphragm and gasket, then tighten down yet. - 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 ...
Instruction Manual
Page 99
... engine running problems, b 3.7 - 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 in perfect condition. Remove the carburetor, b 12.5 - even very minor damage can result in the reverse sequence. 98 MS 231, MS 231 C, MS 251, MS 251 C Inspect the intake manifold and replace it...
... engine running problems, b 3.7 - 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 in perfect condition. Remove the carburetor, b 12.5 - even very minor damage can result in the reverse sequence. 98 MS 231, MS 231 C, MS 251, MS 251 C Inspect the intake manifold and replace it...
Instruction Manual
Page 100
... the tank vent and replace it if necessary. Remove the carburetor, b 12.5 MS 231, MS 231 C, MS 251, MS 251 C 99 Reassemble all other parts in the fuel tank. Close the tank cap. - 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 and connect the pump (2) 0000 850 1300 to the nipple (arrow) - Models with manual fuel pump, b 12.4.1 - Open the fuel tank cap and drain the fuel tank, b 1. - Clean the area around the tank vent. - create a...
... the tank vent and replace it if necessary. Remove the carburetor, b 12.5 MS 231, MS 231 C, MS 251, MS 251 C 99 Reassemble all other parts in the fuel tank. Close the tank cap. - 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 and connect the pump (2) 0000 850 1300 to the nipple (arrow) - Models with manual fuel pump, b 12.4.1 - Open the fuel tank cap and drain the fuel tank, b 1. - Clean the area around the tank vent. - create a...
Instruction Manual
Page 102
... in the reverse sequence. : Take out the screw (1). 1 2310RA371 TG 12.11 Fuel Intake 12.11.1 Pickup Body Any impurities mixed with manual fuel pump, b 12.4.1 2310RA374 TG MS 231, MS 231 C, MS 251, MS 251 C 101 2310RA372 TG 2310RA373 TG - Open the tank cap. 2310RA365 TG : Insert and tighten down the screw (1) firmly. - Open the tank...
... in the reverse sequence. : Take out the screw (1). 1 2310RA371 TG 12.11 Fuel Intake 12.11.1 Pickup Body Any impurities mixed with manual fuel pump, b 12.4.1 2310RA374 TG MS 231, MS 231 C, MS 251, MS 251 C 101 2310RA372 TG 2310RA373 TG - Open the tank cap. 2310RA365 TG : Insert and tighten down the screw (1) firmly. - Open the tank...
Instruction Manual
Page 105
.... : Insert and tighten down the screw (2) firmly. : Ease the handlebar (1) sideways and place it down firmly. : Fit the AV spring (1) in the reverse sequence. 104 MS 231, MS 231 C, MS 251, MS 251 C Machines with manual fuel pump, b 12.4.1 - Insert the screws and tighten them down the screw (2) firmly. -
.... : Insert and tighten down the screw (2) firmly. : Ease the handlebar (1) sideways and place it down firmly. : Fit the AV spring (1) in the reverse sequence. 104 MS 231, MS 231 C, MS 251, MS 251 C Machines with manual fuel pump, b 12.4.1 - Insert the screws and tighten them down the screw (2) firmly. -