Instruction Manual
Page 2
... 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 12.4 Air Guide Shroud 83 12.4.1 Air Guide Shroud - Troubleshooting 8 3.1 Clutch 8 3.2 Chain Drive, Chain Brake, Chain Tensioner 9 3.3 Chain ...24 5.4.1 Adjusting the brake cable 26 5.4.2 Brake cable Removing and Installing 27 5.5 Chain Tensioner 29 5.5.1 Quick Chain Tensioner 30 5.5.2 Chain Catcher 30 5.6 Bar Mounting Stud 31 6. Chain Brake 20 5.1 Checking Operation 20 5.2 Brake Band 20 5.3 Brake Lever 21 5.4...
... 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 12.4 Air Guide Shroud 83 12.4.1 Air Guide Shroud - Troubleshooting 8 3.1 Clutch 8 3.2 Chain Drive, Chain Brake, Chain Tensioner 9 3.3 Chain ...24 5.4.1 Adjusting the brake cable 26 5.4.2 Brake cable Removing and Installing 27 5.5 Chain Tensioner 29 5.5.1 Quick Chain Tensioner 30 5.5.2 Chain Catcher 30 5.6 Bar Mounting Stud 31 6. Chain Brake 20 5.1 Checking Operation 20 5.2 Brake Band 20 5.3 Brake Lever 21 5.4...
Instruction Manual
Page 5
... cover, saw chain and guide bar before re-installing - The specifications must be maintained when tightening down screws, nuts and other fasteners in line with STIHL press fluid and then push the new hoses on to the hose barbs, b 14. hose barb connectors Pull off or push on ... the safety precautions and warnings in position - Do not cut open fuel hoses with the aid of engine damage due to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C Other press fluids are heated for operations in certain conditions. there is an extremely flammable fuel and can be explosive in which occur ...
... cover, saw chain and guide bar before re-installing - The specifications must be maintained when tightening down screws, nuts and other fasteners in line with STIHL press fluid and then push the new hoses on to the hose barbs, b 14. hose barb connectors Pull off or push on ... the safety precautions and warnings in position - Do not cut open fuel hoses with the aid of engine damage due to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C Other press fluids are heated for operations in certain conditions. there is an extremely flammable fuel and can be explosive in which occur ...
Instruction Manual
Page 6
...: Crankcase leakage test at gauge pressure: under vacuum: 2.2 Fuel System 2.3 Ignition System 2.4 Chain Lubrication MS 231 40.6 cm3 41.5 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... (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 2.
...: Crankcase leakage test at gauge pressure: under vacuum: 2.2 Fuel System 2.3 Ignition System 2.4 Chain Lubrication MS 231 40.6 cm3 41.5 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... (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 2.
Instruction Manual
Page 7
... used in polymer and light metal components. 2.5 Tightening Torques DG and P (Plastoform) screws are installed for bar / engine housing 16.0 (repair solution) P 5x18 Cover, chain brake / engine housing 4.0 M 5 Filter base / baffle / carburetor 3.5 P 6x26.5 Handlebar / tank housing, right 6.0 M 5x16 Handlebar / tank housing, bottom 5.0 ...P 6x28 Engine housing / bearing plug 6.0 D 4x16 Oil pump 4.0 M 5x16 Muffler / cylinder 10.0 M 8x1 Flywheel / crankshaft 28.0 P 4x10 Retainer 1.0 Q B 2), 3) 2) 1), 3) 1), 3) 1), 3) 2), 3) 4) 6 MS 231, MS 231 C, MS 251, MS 251 C
... used in polymer and light metal components. 2.5 Tightening Torques DG and P (Plastoform) screws are installed for bar / engine housing 16.0 (repair solution) P 5x18 Cover, chain brake / engine housing 4.0 M 5 Filter base / baffle / carburetor 3.5 P 6x26.5 Handlebar / tank housing, right 6.0 M 5x16 Handlebar / tank housing, bottom 5.0 ...P 6x28 Engine housing / bearing plug 6.0 D 4x16 Oil pump 4.0 M 5x16 Muffler / cylinder 10.0 M 8x1 Flywheel / crankshaft 28.0 P 4x10 Retainer 1.0 Q B 2), 3) 2) 1), 3) 1), 3) 1), 3) 2), 3) 4) 6 MS 231, MS 231 C, MS 251, MS 251 C
Instruction Manual
Page 8
... for polymer: DG and P screws max. 500 rpm Do not use an impact wrench for releasing or tightening screws. MS 231, MS 231 C, MS 251, MS 251 C 7 Coat micro-encapsulated screws with and without binding heads. Fastener Thread size For component Torque Nm Remarks Screw Screw ... Remarks: 1) Screws with binding head 2) Micro-encapsulated screws 3) Waxed screws 4) Degrease crankshaft/flywheel and mount oil-free Q) QuickStop Super B) Quick chain adjuster Use the following procedure when refitting a DG or P screw in an existing thread: Place the screw in the existing thread and does not...
... for polymer: DG and P screws max. 500 rpm Do not use an impact wrench for releasing or tightening screws. MS 231, MS 231 C, MS 251, MS 251 C 7 Coat micro-encapsulated screws with and without binding heads. Fastener Thread size For component Torque Nm Remarks Screw Screw ... Remarks: 1) Screws with binding head 2) Micro-encapsulated screws 3) Waxed screws 4) Degrease crankshaft/flywheel and mount oil-free Q) QuickStop Super B) Quick chain adjuster Use the following procedure when refitting a DG or P screw in an existing thread: Place the screw in the existing thread and does not...
Instruction Manual
Page 9
... under full load Cause Clutch shoes badly worn Clutch drum badly worn Remedy Install new clutch Install new clutch drum Saw chain rotates at idle speed Engine idle speed too high Clutch springs stretched Clutch springs broken Readjust idle speed screw LA Replace the clutch springs or ... Clutch shoe retainer broken Clutch shoes and carrier worn Replace all clutch springs Fit new needle cage Install new retainer or clutch Install new clutch 8 MS 231, MS 231 C, MS 251, MS 251 C
... under full load Cause Clutch shoes badly worn Clutch drum badly worn Remedy Install new clutch Install new clutch drum Saw chain rotates at idle speed Engine idle speed too high Clutch springs stretched Clutch springs broken Readjust idle speed screw LA Replace the clutch springs or ... Clutch shoe retainer broken Clutch shoes and carrier worn Replace all clutch springs Fit new needle cage Install new retainer or clutch Install new clutch 8 MS 231, MS 231 C, MS 251, MS 251 C
Instruction Manual
Page 10
...drum badly worn Brake band blocked Install new clutch Install new clutch drum Check freedom of movement and operation of brake band Saw chain rotates at idle speed Engine idle speed too high Clutch springs stretched Clutch springs broken Readjust idle speed screw LA Replace the clutch... springs or install new clutch Replace the clutch springs Saw chain does not stop immediately when brake is activated Brake spring stretched or broken Fit new brake spring Brake band stretched or worn Clutch drum worn Fit new brake band Install new clutch drum MS 231, MS 231 C, MS 251, MS 251 C 9
...drum badly worn Brake band blocked Install new clutch Install new clutch drum Check freedom of movement and operation of brake band Saw chain rotates at idle speed Engine idle speed too high Clutch springs stretched Clutch springs broken Readjust idle speed screw LA Replace the clutch... springs or install new clutch Replace the clutch springs Saw chain does not stop immediately when brake is activated Brake spring stretched or broken Fit new brake spring Brake band stretched or worn Clutch drum worn Fit new brake band Install new clutch drum MS 231, MS 231 C, MS 251, MS 251 C 9
Instruction Manual
Page 12
... Install new engine housing Oil pump delivers insufficient oil Oil pump damaged or worn Worm driver is loose Install new oil pump Install new worm MS 231, MS 231 C, MS 251, MS 251 C 11 rectify other sources of trouble with the chain lubrication system, check and .
... Install new engine housing Oil pump delivers insufficient oil Oil pump damaged or worn Worm driver is loose Install new oil pump Install new worm MS 231, MS 231 C, MS 251, MS 251 C 11 rectify other sources of trouble with the chain lubrication system, check and .
Instruction Manual
Page 17
... - throttle shutter completely closed Tank vent faulty Clean the carburetor Reset low speed screw (L) correctly Reset idle speed screw (LA) correctly Replace tank vent Saw chain rotates at idle speed Leak on fuel hose from tank to carburetor Seal connections or install new fuel hose Engine idle speed too high Readjust... screw LA (counterclockwise) Clutch springs stretched or fatigued Replace the clutch springs or install new clutch Clutch spring hooks broken Replace the clutch springs 16 MS 231, MS 231 C, MS 251, MS 251 C
... - throttle shutter completely closed Tank vent faulty Clean the carburetor Reset low speed screw (L) correctly Reset idle speed screw (LA) correctly Replace tank vent Saw chain rotates at idle speed Leak on fuel hose from tank to carburetor Seal connections or install new fuel hose Engine idle speed too high Readjust... screw LA (counterclockwise) Clutch springs stretched or fatigued Replace the clutch springs or install new clutch Clutch spring hooks broken Replace the clutch springs 16 MS 231, MS 231 C, MS 251, MS 251 C
Instruction Manual
Page 21
... the throttle wide and let go of the lockout lever on the rear handle - the chain must come areas on the chain saw. the chain must not rotate. : Pry the brake band (2) out of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C The clutch drum must come to the eye. Troubleshooting, b 3.2 - Contamination (with QuickStop Super - Remove...
... the throttle wide and let go of the lockout lever on the rear handle - the chain must come areas on the chain saw. the chain must not rotate. : Pry the brake band (2) out of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C The clutch drum must come to the eye. Troubleshooting, b 3.2 - Contamination (with QuickStop Super - Remove...
Instruction Manual
Page 22
Disengage the chain brake : Hold the brake band (1) sideways, attach it to disconnect the brake spring (1) from the brake lever. 2310RA015 TG MS 231, MS 231 C, MS 251, MS 251 C 21 Reassemble all other checks, b 5.1 - Remove the brake spring from the anchor pin (arrow). - Remove the fan housing, b 8.2 1 - The... underside of the machine and tighten it in the direction of its seat. 2310RA009 TG 2310RA012 TG 1 The clutch drum must rotate freely when the chain brake is disengaged. 2 : Push the brake band (1) into its seat (arrow) as far as stop. - Remove the brake band, b ...
Disengage the chain brake : Hold the brake band (1) sideways, attach it to disconnect the brake spring (1) from the brake lever. 2310RA015 TG MS 231, MS 231 C, MS 251, MS 251 C 21 Reassemble all other checks, b 5.1 - Remove the brake spring from the anchor pin (arrow). - Remove the fan housing, b 8.2 1 - The... underside of the machine and tighten it in the direction of its seat. 2310RA009 TG 2310RA012 TG 1 The clutch drum must rotate freely when the chain brake is disengaged. 2 : Push the brake band (1) into its seat (arrow) as far as stop. - Remove the brake band, b ...
Instruction Manual
Page 25
... : Take the brake lever (2) out of the flat spring (1) into its seat (arrow) as far as stop. 2310RA020 TG 24 MS 231, MS 231 C, MS 251, MS 251 C Check the cam on Machines with QuickStop Super 2 2 - if it is now relaxed. : Use the assembly tool 1117 890 0900...the pivot pins, b 14 1 1 : Disconnect the spring (1) from the brake lever. 2 2310RA034 TG Installing - Remove the shroud, b 6.4 - Engage the chain brake. TOP 2310RA031 TG - Clean the pivot pins and disassembled parts, b 14 - Remove the brake spring from the anchor pin (arrow). - Remove the brake ...
... : Take the brake lever (2) out of the flat spring (1) into its seat (arrow) as far as stop. 2310RA020 TG 24 MS 231, MS 231 C, MS 251, MS 251 C Check the cam on Machines with QuickStop Super 2 2 - if it is now relaxed. : Use the assembly tool 1117 890 0900...the pivot pins, b 14 1 1 : Disconnect the spring (1) from the brake lever. 2 2310RA034 TG Installing - Remove the shroud, b 6.4 - Engage the chain brake. TOP 2310RA031 TG - Clean the pivot pins and disassembled parts, b 14 - Remove the brake spring from the anchor pin (arrow). - Remove the brake ...
Instruction Manual
Page 27
... the mark (a). If the groove in hand guard, b 14 - Troubleshooting, b 3.2 - Remove the chain brake cover, b 5.2 The brake cable must rotate freely. - Free travel . - Troubleshooting, b 3.2 TOP 2310RA043 TG : Attach the spring (1) to the brake lever (arrow). 26 MS 231, MS 231 C, MS 251, MS 251 C Adjust the brake cable, b 5.4.1 - If this is released. : Carefully press the lockout lever...
... the mark (a). If the groove in hand guard, b 14 - Troubleshooting, b 3.2 - Remove the chain brake cover, b 5.2 The brake cable must rotate freely. - Free travel . - Troubleshooting, b 3.2 TOP 2310RA043 TG : Attach the spring (1) to the brake lever (arrow). 26 MS 231, MS 231 C, MS 251, MS 251 C Adjust the brake cable, b 5.4.1 - If this is released. : Carefully press the lockout lever...
Instruction Manual
Page 30
... will vary. - Check position of fuel return hose and correct if necessary, b 12.11.3 - Check operation and adjust the brake cable, b 5.4.1 2310RA060 TG 2710RA079 TG 5.5 Chain Tensioner 2310RA066 TG : Attach the brake cable (1) to the bore (arrow) in the reverse sequence. - Lift the tank housing and secure it into its seat... the tank housing make sure the grommet (1) is pushed fully into the adjusting screw (2) - Install the switch lever, b 10.3.1 - Troubleshooting, b 3.2 2 3 - Install the throttle trigger, b 10.3 MS 231, MS 231 C, MS 251, MS 251 C 29
... will vary. - Check position of fuel return hose and correct if necessary, b 12.11.3 - Check operation and adjust the brake cable, b 5.4.1 2310RA060 TG 2710RA079 TG 5.5 Chain Tensioner 2310RA066 TG : Attach the brake cable (1) to the bore (arrow) in the reverse sequence. - Lift the tank housing and secure it into its seat... the tank housing make sure the grommet (1) is pushed fully into the adjusting screw (2) - Install the switch lever, b 10.3.1 - Troubleshooting, b 3.2 2 3 - Install the throttle trigger, b 10.3 MS 231, MS 231 C, MS 251, MS 251 C 29
Instruction Manual
Page 31
... wing nut (1) and replace if necessary 30 MS 231, MS 231 C, MS 251, MS 251 C When installing the adjusting wheel, make sure its teeth face the cover plate. - If the chain catcher is damaged or worn, install a replacement chain catcher. 2310RA045 TG 5.5.1 Quick Chain Tensioner The quick chain tensioner is an integral part of the sprocket ...down until it out of the sprocket cover (1). - Clean all disassembled parts, b 14 - Reassemble in the reverse sequence. 1 : Position the replacement chain catcher (1) so that it lines up with STIHL multipurpose grease, b 14 -
... wing nut (1) and replace if necessary 30 MS 231, MS 231 C, MS 251, MS 251 C When installing the adjusting wheel, make sure its teeth face the cover plate. - If the chain catcher is damaged or worn, install a replacement chain catcher. 2310RA045 TG 5.5.1 Quick Chain Tensioner The quick chain tensioner is an integral part of the sprocket ...down until it out of the sprocket cover (1). - Clean all disassembled parts, b 14 - Reassemble in the reverse sequence. 1 : Position the replacement chain catcher (1) so that it lines up with STIHL multipurpose grease, b 14 -
Instruction Manual
Page 32
...stud - Reassemble all other parts in the reverse sequence. Screw home the collar stud and tighten it engages the existing thread. - MS 231, MS 231 C, MS 251, MS 251 C 31 In such a case use the collar stud in the engine housing is no longer guaranteed. the security of the collar ...stud (1) with threadlocking adhesive, fit and tighten down firmly. - do not re-drill the hole. - Remove the chain sprocket cover. 2 1 Repair solution ...
...stud - Reassemble all other parts in the reverse sequence. Screw home the collar stud and tighten it engages the existing thread. - MS 231, MS 231 C, MS 251, MS 251 C 31 In such a case use the collar stud in the engine housing is no longer guaranteed. the security of the collar ...stud (1) with threadlocking adhesive, fit and tighten down firmly. - do not re-drill the hole. - Remove the chain sprocket cover. 2 1 Repair solution ...
Instruction Manual
Page 79
...-position it and replace if necessary. - Installing - Troubleshooting, b 3.3 - Open the oil tank cap and drain the oil tank. 1 - Reassemble all other parts in a clean container, b 1 - Chain Lubrication 11.1 Pickup Body 11.2 Oil Suction Hose Impurities gradually clog the fine pores of the filter with minute particles of the tab (arrow) must... oil tank and the pickup body. - the straight side of dirt. Push the oil suction hose (1), pickup body first, through the housing bore (arrow). 78 MS 231, MS 231 C, MS 251, MS 251 C 11.
...-position it and replace if necessary. - Installing - Troubleshooting, b 3.3 - Open the oil tank cap and drain the oil tank. 1 - Reassemble all other parts in a clean container, b 1 - Chain Lubrication 11.1 Pickup Body 11.2 Oil Suction Hose Impurities gradually clog the fine pores of the filter with minute particles of the tab (arrow) must... oil tank and the pickup body. - the straight side of dirt. Push the oil suction hose (1), pickup body first, through the housing bore (arrow). 78 MS 231, MS 231 C, MS 251, MS 251 C 11.
Instruction Manual
Page 96
...H - the ignition module limits maximum engine speed to carry out the basic setting after cleaning and adjusting the carburetor from scratch. Check chain tension and adjust if necessary. - The setting disc 5910 893 6600 may be replaced or after removing the limiter cap. Use the ... or replace if necessary, b 12.1 1 2 : Starting with the high speed screw H (1) against its seat, open it 1 full turn counterclockwise - MS 231, MS 231 C, MS 251, MS 251 C 95 Adjust engine speed with idle speed screw (LA), to 3,300 rpm. 2310RA282 TG For the sake of ± 200 rpm. 14 12 0...
...H - the ignition module limits maximum engine speed to carry out the basic setting after cleaning and adjusting the carburetor from scratch. Check chain tension and adjust if necessary. - The setting disc 5910 893 6600 may be replaced or after removing the limiter cap. Use the ... or replace if necessary, b 12.1 1 2 : Starting with the high speed screw H (1) against its seat, open it 1 full turn counterclockwise - MS 231, MS 231 C, MS 251, MS 251 C 95 Adjust engine speed with idle speed screw (LA), to 3,300 rpm. 2310RA282 TG For the sake of ± 200 rpm. 14 12 0...
Instruction Manual
Page 97
...speed screw (LA) after every correction to change the setting of the high speed screw H and the low speed screw L . Saw chain runs while engine is correct) Idle setting too lean. - It is usually necessary to the low speed screw (L). If the setting ...if necessary. - Turn low speed screw (L) counterclockwise until the chain stops running , then turn it back 1 full turn . - Carry out standard setting. - Warm up the engine. The setting of lubrication and overheating. 96 MS 231, MS 231 C, MS 251, MS 251 C Adjusting engine idle speed - Turn the high speed screw (H)...
...speed screw (LA) after every correction to change the setting of the high speed screw H and the low speed screw L . Saw chain runs while engine is correct) Idle setting too lean. - It is usually necessary to the low speed screw (L). If the setting ...if necessary. - Turn low speed screw (L) counterclockwise until the chain stops running , then turn it back 1 full turn . - Carry out standard setting. - Warm up the engine. The setting of lubrication and overheating. 96 MS 231, MS 231 C, MS 251, MS 251 C Adjusting engine idle speed - Turn the high speed screw (H)...