Instruction Manual
Page 2
... 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. Troubleshooting 8 3.1 Clutch 8 3.2 Chain Drive, Chain Brake, Chain Tensioner 9 3.3 Chain Lubrication 11 3.4 Rewind Starter 12 3.5 Ignition System 14 3.6 Carburetor 15 3.7 Engine 18 4. Contents 1. Models with QuickStop Super 24 5.4.1 Adjusting...
... 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. Troubleshooting 8 3.1 Clutch 8 3.2 Chain Drive, Chain Brake, Chain Tensioner 9 3.3 Chain Lubrication 11 3.4 Rewind Starter 12 3.5 Ignition System 14 3.6 Carburetor 15 3.7 Engine 18 4. Contents 1. Models with QuickStop Super 24 5.4.1 Adjusting...
Instruction Manual
Page 5
...before carrying out repairs or mounting the machine to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C Avoid damaging the hose barb - Always use sharp-edged pliers, screwdrivers, etc. replace as the safety precautions and warnings in the course of STIHL press fluid, b 14. Fuel system - They can be ...machine is started up in the instruction manual. Coat the ends of heat near the fuel. Preparations for servicing Remove the chain sprocket cover, saw chain and guide bar before re-installing - Storing and disposing of oils and fuels Collect fuel or lubricating oil in a ...
...before carrying out repairs or mounting the machine to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C Avoid damaging the hose barb - Always use sharp-edged pliers, screwdrivers, etc. replace as the safety precautions and warnings in the course of STIHL press fluid, b 14. Fuel system - They can be ...machine is started up in the instruction manual. Coat the ends of heat near the fuel. Preparations for servicing Remove the chain sprocket cover, saw chain and guide bar before re-installing - Storing and disposing of oils and fuels Collect fuel or lubricating oil in a ...
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
... 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 These screws form a permanent thread when they are used in polymer and light metal components. They can be removed and installed as often as... Collar screw Screw Nut Screw Screw Screw Screw Screw Screw Screw Screw Screw Carrier Screw Screw Screw Nut Screw P 4x12 Chain tensioner cover 1.5 P 5x18 Antivibration element / engine housing 4.0 P 5x34 Antivibration element / tank housing 4.0 P 4x12...
... 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 These screws form a permanent thread when they are used in polymer and light metal components. They can be removed and installed as often as... Collar screw Screw Nut Screw Screw Screw Screw Screw Screw Screw Screw Screw Carrier Screw Screw Screw Nut Screw P 4x12 Chain tensioner cover 1.5 P 5x18 Antivibration element / engine housing 4.0 P 5x34 Antivibration element / tank housing 4.0 P 4x12...
Instruction Manual
Page 8
... Cylinder / engine housing 2.0 1.6 12.0 4.5 11.0 1), 3) 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 form... that the screw engages properly in the hole and rotate it counterclockwise until it drops down slightly. Tighten the screw clockwise to the specified torque. MS 231, MS 231 C, MS 251, MS 251 C 7
... Cylinder / engine housing 2.0 1.6 12.0 4.5 11.0 1), 3) 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 form... that the screw engages properly in the hole and rotate it counterclockwise until it drops down slightly. Tighten the screw clockwise to the specified torque. MS 231, MS 231 C, MS 251, MS 251 C 7
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 3.3 Chain Lubrication In the event of faults before disassembling the oil pump.
... 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 3.3 Chain Lubrication In the event of faults before disassembling the oil pump.
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 cover (2). 219RA049 TG Machines with chain oil, chips, fine particles of abrasion, etc.) and smoothing of the friction surfaces of the brake band and clutch drum impair the coefficient of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C Contamination (with QuickStop Super - ...Starting the engine 2 1 - With the chain brake activated (locked), open the throttle wide and activate the brake manually - Remove...
...the cover (2). 219RA049 TG Machines with chain oil, chips, fine particles of abrasion, etc.) and smoothing of the friction surfaces of the brake band and clutch drum impair the coefficient of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C Contamination (with QuickStop Super - ...Starting the engine 2 1 - With the chain brake activated (locked), open the throttle wide and activate the brake manually - Remove...
Instruction Manual
Page 22
... : 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 Engage the chain brake. 1 2 TOP 2 TOP 1 2310RA011 TG : Place the cover (1) in the slots (arrows) first. - Reassemble all other checks, b 5.1 - Remove the fan housing, b ...: Fit the screw (2) on the underside of its seat. 2310RA009 TG 2310RA012 TG 1 The clutch drum must rotate freely when the chain brake is now relaxed. : Use the assembly tool 1117 890 0900 to the brake lever (2) and then swing it down the screws...
... : 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 Engage the chain brake. 1 2 TOP 2 TOP 1 2310RA011 TG : Place the cover (1) in the slots (arrows) first. - Reassemble all other checks, b 5.1 - Remove the fan housing, b ...: Fit the screw (2) on the underside of its seat. 2310RA009 TG 2310RA012 TG 1 The clutch drum must rotate freely when the chain brake is now relaxed. : Use the assembly tool 1117 890 0900 to the brake lever (2) and then swing it down the screws...
Instruction Manual
Page 25
... brake lever. 2310RA033 TG 1 : 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 anchor pin - Troubleshooting, b 3.2 - Remove the brake band, b 5.2 1 1 TOP : Pull the hand guard (1) and brake lever (2) off the pivot pins (arrows) together. - if... spring (1) from the anchor pin (arrow). - Lubricate the pivot pins, b 14 1 1 : Disconnect the spring (1) from the anchor pin (arrow). : Disconnect the brake cable (1). - Engage the chain brake.
... brake lever. 2310RA033 TG 1 : 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 anchor pin - Troubleshooting, b 3.2 - Remove the brake band, b 5.2 1 1 TOP : Pull the hand guard (1) and brake lever (2) off the pivot pins (arrows) together. - if... spring (1) from the anchor pin (arrow). - Lubricate the pivot pins, b 14 1 1 : Disconnect the spring (1) from the anchor pin (arrow). : Disconnect the brake cable (1). - Engage the chain brake.
Instruction Manual
Page 27
...the adjustment of the brake spring must rotate freely. - A certain amount of free travel is necessary to the brake lever (arrow). 26 MS 231, MS 231 C, MS 251, MS 251 C Press down the lockout lever (1) and hold it in hand guard, b 14 - If this is in the reverse sequence. 1 2310RA028...2 1 1 TOP 1 2310RA042 TG 2310RA031 TG 2310RA044 TG TOP : Attach the spring (1) to the brake lever (arrow) so that position. Remove the chain brake cover, b 5.2 The brake cable must be depressed without the brake lever moving. Free travel . - Lubricate the brake lever, flat spring and slot...
...the adjustment of the brake spring must rotate freely. - A certain amount of free travel is necessary to the brake lever (arrow). 26 MS 231, MS 231 C, MS 251, MS 251 C Press down the lockout lever (1) and hold it in hand guard, b 14 - If this is in the reverse sequence. 1 2310RA028...2 1 1 TOP 1 2310RA042 TG 2310RA031 TG 2310RA044 TG TOP : Attach the spring (1) to the brake lever (arrow) so that position. Remove the chain brake cover, b 5.2 The brake cable must be depressed without the brake lever moving. Free travel . - Lubricate the brake lever, flat spring and slot...
Instruction Manual
Page 30
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 brake lever (2). 2 1 : Slide the brake cable ...spur gear (2) and tensioner slide (1). 1 2310RA063 TG : Position the brake cable (1) in the reverse sequence. - Troubleshooting, b 3.2 2 3 - Install the throttle trigger, b 10.3 MS 231, MS 231 C, MS 251, MS 251 C 29 Check position of fuel return hose and correct if necessary, b 12.11.3 - Install the switch lever, b 10.3.1 - 1 2 1 2 - Lift the tank housing ...
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 brake lever (2). 2 1 : Slide the brake cable ...spur gear (2) and tensioner slide (1). 1 2310RA063 TG : Position the brake cable (1) in the reverse sequence. - Troubleshooting, b 3.2 2 3 - Install the throttle trigger, b 10.3 MS 231, MS 231 C, MS 251, MS 251 C 29 Check position of fuel return hose and correct if necessary, b 12.11.3 - Install the switch lever, b 10.3.1 - 1 2 1 2 - Lift the tank housing ...
Instruction Manual
Page 31
... it snaps into position. 1 2 1 The chain catcher (arrow) is installed in the reverse sequence. 1 : Position the replacement chain catcher (1) so that it out of the wing nut (1) and carefully pry it lines up with STIHL multipurpose grease, b 14 - Swing the wing ... wing nut (1) and replace if necessary 30 MS 231, MS 231 C, MS 251, MS 251 C Reassemble in the reverse sequence. - Reassemble in the sprocket cover. 1 2 : Take out the screw (arrow). : Remove the cover plate (1) and adjusting wheel (2). Remove the chain sprocket cover. 165RA007 TG 533RA058 TG 2310RA048 TG...
... it snaps into position. 1 2 1 The chain catcher (arrow) is installed in the reverse sequence. 1 : Position the replacement chain catcher (1) so that it out of the wing nut (1) and carefully pry it lines up with STIHL multipurpose grease, b 14 - Swing the wing ... wing nut (1) and replace if necessary 30 MS 231, MS 231 C, MS 251, MS 251 C Reassemble in the reverse sequence. - Reassemble in the sprocket cover. 1 2 : Take out the screw (arrow). : Remove the cover plate (1) and adjusting wheel (2). Remove the chain sprocket cover. 165RA007 TG 533RA058 TG 2310RA048 TG...
Instruction Manual
Page 32
5.6 Bar Mounting Stud - Remove the chain sprocket cover. 2 1 Repair solution If the thread in the screw list as a repair solution, b 2.5. 1 2310RA046 TG 2310RA047 TG : Push stud puller 5910 893 0501 (1) over ... of the collar stud is badly damaged or stripped it will not be possible to tighten the standard collar stud to the specified torque - MS 231, MS 231 C, MS 251, MS 251 C 31 Fit the collar stud by hand so that it down firmly, b 14 - Reassemble all other parts in the reverse sequence. the security of...
5.6 Bar Mounting Stud - Remove the chain sprocket cover. 2 1 Repair solution If the thread in the screw list as a repair solution, b 2.5. 1 2310RA046 TG 2310RA047 TG : Push stud puller 5910 893 0501 (1) over ... of the collar stud is badly damaged or stripped it will not be possible to tighten the standard collar stud to the specified torque - MS 231, MS 231 C, MS 251, MS 251 C 31 Fit the collar stud by hand so that it down firmly, b 14 - Reassemble all other parts in the reverse sequence. the security of...
Instruction Manual
Page 79
... 1 2310RA301 TG Do not overstretch the suction hose. - 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 Check position of the tab (arrow) must locate against the housing. - Remove the clutch, b 4 - Pull off the pickup body (1), check... the oil tank if necessary, b1 : Line up the oil suction hose (1) - This prevents the oil pump from the oil tank. Chain Lubrication 11.1 Pickup Body 11.2 Oil Suction Hose Impurities gradually clog the fine pores of dirt. Reassemble all other parts in the engine housing...
... 1 2310RA301 TG Do not overstretch the suction hose. - 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 Check position of the tab (arrow) must locate against the housing. - Remove the clutch, b 4 - Pull off the pickup body (1), check... the oil tank if necessary, b1 : Line up the oil suction hose (1) - This prevents the oil pump from the oil tank. Chain Lubrication 11.1 Pickup Body 11.2 Oil Suction Hose Impurities gradually clog the fine pores of dirt. Reassemble all other parts in the engine housing...
Instruction Manual
Page 96
...) and into the low speed screw L and high speed screw H - Use the idle speed screw (LA) to set engine speed to 3,300 rpm. 4. MS 231, MS 231 C, MS 251, MS 251 C 95 Check chain tension and adjust if necessary. - Warm up the engine. push the screwdriver through the pre-installed limiter cap on the screwdriver 5910 890...
...) and into the low speed screw L and high speed screw H - Use the idle speed screw (LA) to set engine speed to 3,300 rpm. 4. MS 231, MS 231 C, MS 251, MS 251 C 95 Check chain tension and adjust if necessary. - Warm up the engine. push the screwdriver through the pre-installed limiter cap on the screwdriver 5910 890...
Instruction Manual
Page 97
Adjusting engine idle speed - Saw chain runs while engine is a risk of engine damage as a result of lack of lubrication and overheating. 96 MS 231, MS 231 C, MS 251, MS 251 C Turn the adjusting screws only very slightly. If the setting is made too lean there is idling - Troubleshooting, b 3.6 - Warm up the engine. - Turn the idle ...
Adjusting engine idle speed - Saw chain runs while engine is a risk of engine damage as a result of lack of lubrication and overheating. 96 MS 231, MS 231 C, MS 251, MS 251 C Turn the adjusting screws only very slightly. If the setting is made too lean there is idling - Troubleshooting, b 3.6 - Warm up the engine. - Turn the idle ...