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. Contents 1. Introduction and Safety Precautions 3 1.1 Introduction 3 1.2 Safety Precautions 4 2. Chain Brake 20 5.1 Checking Operation 20 5.2 Brake Band 20 5.3 Brake Lever 21 5.4 Brake...
... 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. Contents 1. Introduction and Safety Precautions 3 1.1 Introduction 3 1.2 Safety Precautions 4 2. Chain Brake 20 5.1 Checking Operation 20 5.2 Brake Band 20 5.3 Brake Lever 21 5.4 Brake...
Instruction Manual
Page 3
... and Installing 100 12.11 Fuel Intake 101 12.11.1 Pickup Body 101 12.11.2 Fuel Hose 101 12.11.3 Fuel Hoses - Servicing Aids 112 2 MS 231, MS 231 C, MS 251, MS 251 C
... and Installing 100 12.11 Fuel Intake 101 12.11.1 Pickup Body 101 12.11.2 Fuel Hose 101 12.11.3 Fuel Hoses - Servicing Aids 112 2 MS 231, MS 231 C, MS 251, MS 251 C
Instruction Manual
Page 4
.... Refer to the latest edition of the illustrated parts lists while carrying out repair work. chapter 4.2 in this power tool. MS 231, MS 231 C, MS 251, MS 251 C 3 The meanings are included in this manual. Engage the bar mounting stud in the outer bore in the mounting plate...help locate the fault, consult the chapter on the machine, may have been introduced since they, depending on "Troubleshooting" and the "STIHL Service Training System" for all the repair and servicing procedures specific to the "Technical Information" bulletins for engineering changes which have several...
.... Refer to the latest edition of the illustrated parts lists while carrying out repair work. chapter 4.2 in this power tool. MS 231, MS 231 C, MS 251, MS 251 C 3 The meanings are included in this manual. Engage the bar mounting stud in the outer bore in the mounting plate...help locate the fault, consult the chapter on the machine, may have been introduced since they, depending on "Troubleshooting" and the "STIHL Service Training System" for all the repair and servicing procedures specific to the "Technical Information" bulletins for engineering changes which have several...
Instruction Manual
Page 5
... with STIHL press fluid and then push the new hoses on tightening torques lists all machine components that have to be tightened to the assembly stand. The high voltages which components are not approved and may result in damage to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C...in accordance with local environmental regulations. 1.2 Safety Precautions If the machine is otherwise a risk of injury from the fanwheel and a risk of STIHL press fluid, b 14. Exercise extreme caution while carrying out maintenance and repair work with a knife or similar tool. Always install new ...
... with STIHL press fluid and then push the new hoses on tightening torques lists all machine components that have to be tightened to the assembly stand. The high voltages which components are not approved and may result in damage to overheating. 4 MS 231, MS 231 C, MS 251, MS 251 C...in accordance with local environmental regulations. 1.2 Safety Precautions If the machine is otherwise a risk of injury from the fanwheel and a risk of STIHL press fluid, b 14. Exercise extreme caution while carrying out maintenance and repair work with a knife or similar tool. Always install new ...
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
... / 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 They can be removed and installed as often as necessary without impairing the strength of the screwed assembly, providing the specified tightening torque is...
... / 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 They can be removed and installed as often as necessary without impairing the strength of the screwed assembly, providing the specified tightening torque is...
Instruction Manual
Page 8
... guide shroud Spark plug / cylinder Ignition module/cylinder Cylinder / engine housing 2.0 1.6 12.0 4.5 11.0 1), 3) Remarks: 1) Screws with medium strength Loctite 242 or 243 before reinstalling. MS 231, MS 231 C, MS 251, MS 251 C 7 Tighten the screw clockwise to the specified torque. This procedure ensures that the screw engages properly in the hole and rotate it counterclockwise until...
... guide shroud Spark plug / cylinder Ignition module/cylinder Cylinder / engine housing 2.0 1.6 12.0 4.5 11.0 1), 3) Remarks: 1) Screws with medium strength Loctite 242 or 243 before reinstalling. MS 231, MS 231 C, MS 251, MS 251 C 7 Tighten the screw clockwise to the specified torque. This procedure ensures that the screw engages properly in the hole and rotate it counterclockwise until...
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 3.
... 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 3.
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
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 - 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
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 13
... turn) ...Models with ErgoStart Guide peg on pawl or pawl itself is difficult to carrier Spring in spring housing fatigued Install new spring housing 12 MS 231, MS 231 C, MS 251, MS 251 C 3.4 Rewind Starter Condition Starter rope broken Cause Remedy Rope pulled out too vigorously as far as stop or over edge, i.e.
... turn) ...Models with ErgoStart Guide peg on pawl or pawl itself is difficult to carrier Spring in spring housing fatigued Install new spring housing 12 MS 231, MS 231 C, MS 251, MS 251 C 3.4 Rewind Starter Condition Starter rope broken Cause Remedy Rope pulled out too vigorously as far as stop or over edge, i.e.
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
... shoes have turned blue Install new flywheel Ignition timing wrong, flywheel out of the spark plug, clean or replace spark plug if necessary. 14 MS 231, MS 231 C, MS 251, MS 251 C 3.5 Ignition System Condition Engine runs roughly, misfires, temporary loss of switch shaft/ contact spring and ignition module Damaged insulation or break in ignition lead...
... shoes have turned blue Install new flywheel Ignition timing wrong, flywheel out of the spark plug, clean or replace spark plug if necessary. 14 MS 231, MS 231 C, MS 251, MS 251 C 3.5 Ignition System Condition Engine runs roughly, misfires, temporary loss of switch shaft/ contact spring and ignition module Damaged insulation or break in ignition lead...
Instruction Manual
Page 16
... control lever sticking on spindle Check the inlet control lever and replace if necessary. foreign matter in accelerator Install new carburetor pump worn or damaged MS 231, MS 231 C, MS 251, MS 251 C 15 3.6 Carburetor Condition Carburetor floods;
... control lever sticking on spindle Check the inlet control lever and replace if necessary. foreign matter in accelerator Install new carburetor pump worn or damaged MS 231, MS 231 C, MS 251, MS 251 C 15 3.6 Carburetor Condition Carburetor floods;
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
... 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 key in carburetor, replace if necessary Leak on fuel hose from tank to carburetor Seal connections or install new fuel hose Setting of...
... 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 key in carburetor, replace if necessary Leak on fuel hose from tank to carburetor Seal connections or install new fuel hose Setting of...
Instruction Manual
Page 19
..., re-seal or replace if necessary. 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 Fuel system - Ignition system Condition Cause Engine does not start easily, stalls Oil seals in fan housing dirty Clean air inlet on the engine...
..., re-seal or replace if necessary. 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 Fuel system - Ignition system Condition Cause Engine does not start easily, stalls Oil seals in fan housing dirty Clean air inlet on the engine...
Instruction Manual
Page 20
.... Remove the needle cage. - 4. Clutch 4.1 Clutch Drum - If it is less than about 80% of wear. Remove and install the clutch drum, see instruction manual. - MS 231, MS 231 C, MS 251, MS 251 C 19 Troubleshooting, b 4.2 -
.... Remove the needle cage. - 4. Clutch 4.1 Clutch Drum - If it is less than about 80% of wear. Remove and install the clutch drum, see instruction manual. - MS 231, MS 231 C, MS 251, MS 251 C 19 Troubleshooting, b 4.2 -
Instruction Manual
Page 21
... (with QuickStop Super - the chain must rotate freely when the lockout lever is less 2 than a second) is measured in terms 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) - The clutch drum must not rotate. : Pry the brake...
... (with QuickStop Super - the chain must rotate freely when the lockout lever is less 2 than a second) is measured in terms 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) - The clutch drum must not rotate. : Pry the brake...
