Instruction Manual
Page 2
... 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. QuickStop Super 75 10.3.3 Choke Rod 76 10.3.4 Throttle Rod 76 11. Chain Brake 20 5.1 Checking Operation 20 5.2 Brake Band 20...
... 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. QuickStop Super 75 10.3.3 Choke Rod 76 10.3.4 Throttle Rod 76 11. Chain Brake 20 5.1 Checking Operation 20 5.2 Brake Band 20...
Instruction Manual
Page 3
Special Servicing Tools 110 14. 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. Contents 12.6 Servicing the Carburetor 90 12.6.1 Metering Diaphragm ...
Special Servicing Tools 110 14. 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. Contents 12.6 Servicing the Carburetor 90 12.6.1 Metering Diaphragm ...
Instruction Manual
Page 4
...use of any replacement parts. Technical information bulletins also supplement the parts list until a revised edition is not shown in the "STIHL Special Tools" manual. Symbols are as follows: In the descriptions: : Action to be taken as shown in position with ...procedures specific to third parties. They must not project since they, depending on "Troubleshooting" and the "STIHL Service Training System" for greater clarity. MS 231, MS 231 C, MS 251, MS 251 C 3 They show the installed positions of this manual. Introduction and Safety Precautions 2710RA320 TG 1.1 ...
...use of any replacement parts. Technical information bulletins also supplement the parts list until a revised edition is not shown in the "STIHL Special Tools" manual. Symbols are as follows: In the descriptions: : Action to be taken as shown in position with ...procedures specific to third parties. They must not project since they, depending on "Troubleshooting" and the "STIHL Service Training System" for greater clarity. MS 231, MS 231 C, MS 251, MS 251 C 3 They show the installed positions of this manual. Introduction and Safety Precautions 2710RA320 TG 1.1 ...
Instruction Manual
Page 5
... the connectors with threadlocking adhesive. Other press fluids are heated for assembly or disassembly. Improper handling may appear alone on to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C do not use original STIHL replacement parts. The specifications must be maintained when tightening down screws, nuts and other fasteners in all machine components that have to...
... the connectors with threadlocking adhesive. Other press fluids are heated for assembly or disassembly. Improper handling may appear alone on to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C do not use original STIHL replacement parts. The specifications must be maintained when tightening down screws, nuts and other fasteners in all machine components that have to...
Instruction Manual
Page 6
...: Clutch: Clutch engages at: 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 13,000 rpm 2,800 rpm Centrifugal clutch ... 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.
...: Clutch: Clutch engages at: 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 13,000 rpm 2,800 rpm Centrifugal clutch ... 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
... baffle / engine housing 2.0 M 12x1 L Carrier / crankshaft 50.0 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
... baffle / engine housing 2.0 M 12x1 L Carrier / crankshaft 50.0 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
... weaken the assembly. Power screwdriver setting 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
... weaken the assembly. Power screwdriver setting 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
Instruction Manual
Page 9
... 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
... 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
... 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
... 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 11
lockout lever not depressed Brake cable overtensioned Remedy Readjust brake cable Reconnect or replace brake cable Adjust brake cable Adjust brake cable 10 MS 231, MS 231 C, MS 251, MS 251 C Condition Cause QuickStop Super Coasting brake does not disengage even though lockout lever is depressed Brake cable stretched Brake cable disconnected or broken QuickStop Super Coasting brake does not disengage properly even though lockout lever is depressed Too much free travel on lockout lever QuickStop Super Braking action of coasting brake inadequate -
lockout lever not depressed Brake cable overtensioned Remedy Readjust brake cable Reconnect or replace brake cable Adjust brake cable Adjust brake cable 10 MS 231, MS 231 C, MS 251, MS 251 C Condition Cause QuickStop Super Coasting brake does not disengage even though lockout lever is depressed Brake cable stretched Brake cable disconnected or broken QuickStop Super Coasting brake does not disengage properly even though lockout lever is depressed Too much free travel on lockout lever QuickStop Super Braking action of coasting brake inadequate -
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 13
... pawls and torsion springs if necessary Lugs on carrier worn Install new carrier Spring loop in spring housing fatigued Install new spring housing 12 MS 231, MS 231 C, MS 251, MS 251 C not vertically Fit new starter rope Normal wear Fit new starter rope Starter rope does not rewind Rewind spring very dirty or corroded Insufficient...
... pawls and torsion springs if necessary Lugs on carrier worn Install new carrier Spring loop in spring housing fatigued Install new spring housing 12 MS 231, MS 231 C, MS 251, MS 251 C not vertically Fit new starter rope Normal wear Fit new starter rope Starter rope does not rewind Rewind spring very dirty or corroded Insufficient...
Instruction Manual
Page 14
Condition Starter rope is difficult to pull or rewinds very slowly Cause Remedy Starter mechanism is very dirty Thoroughly clean complete starter mechanism At very low outside temperatures: Lubricating oil on rewind spring becomes viscous (spring windings stick together) or moisture has got onto the rewind spring (spring windings frozen together) Coat rewind spring with a small amount of standard solvent-based degreasant (containing no chlorinated or halogenated hydrocarbons), then pull rope carefully several times until normal action is restored MS 231, MS 231 C, MS 251, MS 251 C 13
Condition Starter rope is difficult to pull or rewinds very slowly Cause Remedy Starter mechanism is very dirty Thoroughly clean complete starter mechanism At very low outside temperatures: Lubricating oil on rewind spring becomes viscous (spring windings stick together) or moisture has got onto the rewind spring (spring windings frozen together) Coat rewind spring with a small amount of standard solvent-based degreasant (containing no chlorinated or halogenated hydrocarbons), then pull rope carefully several times until normal action is restored MS 231, MS 231 C, MS 251, MS 251 C 13
Instruction Manual
Page 15
... or replace if necessary. 3.5 Ignition System Condition Engine runs roughly, misfires, temporary loss of the spark plug, clean or replace spark plug if necessary. 14 MS 231, MS 231 C, MS 251, MS 251 C
... or replace if necessary. 3.5 Ignition System Condition Engine runs roughly, misfires, temporary loss of the spark plug, clean or replace spark plug if necessary. 14 MS 231, MS 231 C, MS 251, MS 251 C
Instruction Manual
Page 16
foreign matter in accelerator Install new carburetor pump worn or damaged MS 231, MS 231 C, MS 251, MS 251 C 15 Helical spring not located on nipple Remove the inlet control lever and of inlet control lever refit it correctly Perforated disc on diaphragm is ...
foreign matter in accelerator Install new carburetor pump worn or damaged MS 231, MS 231 C, MS 251, MS 251 C 15 Helical spring not located on nipple Remove the inlet control lever and of inlet control lever refit it correctly Perforated disc on diaphragm is ...
Instruction Manual
Page 17
... 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
... 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 18
... extremely rich, has Choke shutter does not open no power and a very low maximum speed Check carburetor and choke shaft, service or replace if necessary MS 231, MS 231 C, MS 251, MS 251 C 17 Condition Cause Engine speed drops quickly under Air filter dirty load -
... extremely rich, has Choke shutter does not open no power and a very low maximum speed Check carburetor and choke shaft, service or replace if necessary MS 231, MS 231 C, MS 251, MS 251 C 17 Condition Cause Engine speed drops quickly under Air filter dirty load -
Instruction Manual
Page 19
... Clean air inlet on the engine: - 3.7 Engine Always check and, if necessary, repair the following parts before looking for faults on fan housing 18 MS 231, MS 231 C, MS 251, MS 251 C Air filter - Air inlets in fan housing blocked or cooling fins on cylinder very dirty Thoroughly clean all cooling air openings and the cylinder...
... Clean air inlet on the engine: - 3.7 Engine Always check and, if necessary, repair the following parts before looking for faults on fan housing 18 MS 231, MS 231 C, MS 251, MS 251 C Air filter - Air inlets in fan housing blocked or cooling fins on cylinder very dirty Thoroughly clean all cooling air openings and the cylinder...
Instruction Manual
Page 20
... (arrow) and the flat side of the clutch drum (1), check the remaining wall thickness. as shown in the reverse sequence. 2310RA005 TG 2310RA003 TG - MS 231, MS 231 C, MS 251, MS 251 C 19 4. If there are signs of serious wear on the inside diameter of its metal top must rest on the crankshaft stub so that...
... (arrow) and the flat side of the clutch drum (1), check the remaining wall thickness. as shown in the reverse sequence. 2310RA005 TG 2310RA003 TG - MS 231, MS 231 C, MS 251, MS 251 C 19 4. If there are signs of serious wear on the inside diameter of its metal top must rest on the crankshaft stub so that...
Instruction Manual
Page 21
..., which prolongs the braking time. the chain must rotate freely when the lockout lever is measured in order if deceleration of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C With the chain brake released, open the throttle wide for a brief 1 TOP period (max. 3 seconds) - 5. Disengage the chain brake 2 OP 1 : Turn the brake band...
..., which prolongs the braking time. the chain must rotate freely when the lockout lever is measured in order if deceleration of the machine. 20 MS 231, MS 231 C, MS 251, MS 251 C With the chain brake released, open the throttle wide for a brief 1 TOP period (max. 3 seconds) - 5. Disengage the chain brake 2 OP 1 : Turn the brake band...