STIHL MS 231, 251 Instruction Manual
English © ANDREAS STIHL AG & Co. KG, 2020 0458-737-8321-B. VB3.J20. 0000006609_008_GB Printed on chlorine-free paper Printing inks contain vegetable oils, paper can be recycled.
English Intake air baffle: winter operation Guide to Using this Manual This Instruction Manual refers to a STIHL chain saw, also called a machine in this Instruction Manual. Intake air baffle: summer operation Pictograms Handle heating Pictograms that appear on the machine are explained in this Instruction Manual.
English Safety Precautions Special safety precautions must be observed to reduce the risk of personal injury when working with a chain saw because of the very high chain speed and very sharp cutters. It is important that you read the instruction manual before first use and keep it in a safe place for future reference. Nonobservance of the instruction manual may result in serious or even fatal injury. General Observe all applicable local safety regulations, standards and ordinances.
English Wear sturdy protective gloves made of a resistant material (e.g. leather). Clean the dust and dirt off the machine – do not use any grease solvents for this purpose. Open the fuel filler cap carefully so that any excess pressure is relieved gradually and fuel does not splash out. Clean the ventilation slots if necessary. The machine may only be refuelled in a well ventilated place. Clean the machine immediately if fuel is spilled.
English – Check operation of chain brake, front hand guard – Correctly mounted guide bar – Correctly tensioned chain – The trigger and trigger lockout must move freely and spring back to the idle position when they are released. – – Master Control lever must move easily to STOP, 0 or † Check that the spark plug boot is secure – a loose boot may cause arcing that could ignite combustible fumes and cause a fire. – Never attempt to modify the controls or safety devices in any way.
English Examine the saw chain periodically at short intervals and as soon as you note any tangible changes: a machine that is not in perfect working order. In case of doubt, have the unit checked by your servicing dealer. – Switch off the engine; wait until the saw chain is stationary – Check condition and secure fitting – Check sharpness Check for correct idling, so that the saw chain stops moving when the throttle trigger is released. Check the idle setting regularly and correct when possible.
English Maintenance and repairs Check ignition lead (insulation in good condition, secure connection). Always switch off the engine before any repair, cleaning or maintenance work and any work on the chain. Risk of injury if the engine starts inadvertently! Check that the muffler is in perfect working condition. Exception: adjustment of carburettor and idle speed. The machine must be serviced regularly. Do not attempt any maintenance or repair work not described in the Instruction Manual.
English Kickback occurs if, for example, The most common reactive forces are: kickback, pushback and pull-in. 001BA257 KN Dangers of kickback Kickback can result in fatal cuts. – – The saw chain in the area of the upper quarter of the guide bar nose unintentionally comes into contact with wood or a solid object – e. g.
English Dead wood (brittle, rotten or dead wood) poses a significant, highly unpredictable hazard. It is extremely difficult or even practically impossible to recognise the danger. Use aids such as winches or draglines. be drawn forward toward the log – to avoid this, engage the bumper spike firmly in the wood. Pushback (B) B 001BA038 KN When felling close to roads, rail lines, power lines, etc., work with particular care. If necessary, notify police, power companies or railway authorities.
English Note when reaching the end of a cut that the saw is no longer supported in the kerf. You have to take the full weight of the machine since it might otherwise go out of control. materials, dry plants or scrub. Always contact your local forest authority for information on a possible fire risk. 001BA082 KN When cutting small logs: – Use a sturdy and stable support – sawhorse. Position the saw so that your body is clear of the cutting attachment. – Never hold the log with your leg or foot.
English Ripping cut: 1 1/ 2 21/2 001BA088 LÄ 2 001BA151 KN 1 1 Maintain a distance of at least 2 1/2 tree lengths from the next felling site. 2 N Make relieving cut at the compression side (1) Make bucking cut at the tension side (2) Be wary of pushback when making bucking cut from the bottom upwards (underbuck). NOTICE Do not cut a lying log at a point where it is touching the ground because the saw chain will otherwise be damaged.
English Preparing work area at base of tree B – – 45° A Felling notch First clear the tree base and work area from interfering limbs and brush to provide a secure footing. Preparing the felling notch Carefully clear the base of the trunk (e.g., with an axe) – sand, stones and other foreign objects will blunt the saw chain C – Establish escape paths for each worker – approx.
English Determine direction of fall with gunning sight on cover and fan housing Checking the direction of fall felling notch to a depth of about 1/10 of trunk diameter. On large diameter trees, cut to no more than width of guide bar. Your chainsaw has a gunning sight on the cover and fan housing. Use this gunning sight. Making the felling notch When making a felling notch, align the chainsaw so that the notch lies at a right angle to the direction of fall.
English The tree is felled with the felling cut (E). – Cut horizontally – 1/10 (at least 3 cm) of tree diameter higher than bottom of felling notch (C). The holding strap (F) or stabilizing strap (G) supports the tree and helps prevent it from falling prematurely. – Width of strip: approx. 1/10 to 1/5 of the trunk diameter – Do not cut into the strip during the felling cut – With rotten trunks, leave a wider strip 1.
English Felling cut with stabilizing strap (normal tree) – Do not cut into the stabilizing strap A) Thin trunks 1. Implement this felling cut when the trunk diameter is smaller than the cutting length of the chainsaw. 2. 3. 3. 5. 001BA263 KN 4. 1. 001BA273 KN 2. 001BA261 KN N Shout a warning before starting the felling cut. Set the felling wedge (3) Shout a second warning immediately before the tree falls.
English N Plunge cut the felling cut N Make the felling cut up to the hinge (4) – Do not cut into the hinge N Make the felling cut up to the stabilizing strap (5) 2. 001BA274 KN 6. N N Plunge cut the guide bar into the trunk until it exits on the other side Shout a second warning immediately before the tree falls.
English The felling cut must be continued on the opposite side of the trunk. B) Thick trunks Ensure that the second cut is at the same level as the first cut. 1. 2.
English Chain Scabbard Cutting Attachment Mounting the Bar and Chain (side chain tensioner) A cutting attachment consists of the saw chain, guide bar and chain sprocket. a – – 3 The pitch (t) of the saw chain (1), chain sprocket and the nose sprocket of the Rollomatic guide bar must match. Your saw comes standard with a chain scabbard that matches the cutting attachment.
English Disengage the chain brake. 1 001BA186 KN 2 4 N Pull the hand guard towards the front handle until there is an audible click – the chain brake is disengaged. 143BA003 KN Fitting the chain N Removing the chain sprocket cover Fit the guide bar over the studs (1) – the cutting edges on the top of the bar must point to the right. N Engage the peg of the tensioner slide in the locating hole (2) –- place the chain over the sprocket (3) at the same time.
English Releasing the chain brake N Fit the saw chain – starting at the nose of the guide bar – pay attention to the position of the tensioning gear and the cutting edges N Turn tensioning gear (1) to the right as far as possible N Turn the guide bar so that the tensioning gear faces the user Remove screw (2) 1 3 N 2310BA016 KN N Pull hand guard towards the front handle until it engages audibly – chain brake is released 2 3 181BA013 KN N 001BA186 KN 2310BA015 KN 2 Fitting the saw chain P
English turn the adjusting wheel (4) a little until the chain sprocket cover can be slid completely against the engine housing N Swing grip (5) into position (until it engages) N Fit wing nut and tighten lightly N Next step: see "Tensioning the Saw Chain" Tensioning the Saw Chain (side chain tensioner) 142BA063 KN N 1 135BA011 KN Retensioning during cutting work: N Guide the drive link into the bar groove (see arrow) and turn the tensioning gear to the left as far as possible N Fit chain spr
English Tensioning the Saw Chain (quick chain tensioner) Checking Chain Tension Fuel Your engine requires a mixture of gasoline and engine oil. 1 142BA064 KN 001BA112 KN 2 WARNING Retensioning during cutting work: N Shut off the engine. N Shut off the engine. N N Pull out the hinged clip and loosen the wingnut. Wear work gloves to protect your hands.
English Engine Oil If you mix the fuel yourself, use only STIHL two-stroke engine oil or another high-performance engine oil in accordance with JASO FB, JASO FC, JASO FD, ISO-L-EGB, ISO-L-EGC or ISO-L-EGD. STIHL specifies STIHL HP Ultra twostroke engine oil or an equivalent highperformance engine oil in order to maintain emission limits over the machine’s service life.
English N Turn the cap counterclockwise (about a quarter turn). 001BA235 KN 001BA234 KN 001BA232 KN Closing N Fold the grip down. Fit the cap – marks on tank cap and fuel tank must line up. N Press the cap down as far as stop. 001BA234 KN N Tank cap is locked. 001BA233 KN Marks on tank cap and fuel tank must line up. 001BA237 KN N Take care not to spill fuel while fueling and do not overfill the tank. STIHL recommends you use the STIHL filler nozzle for fuel (special accessory).
English Left: 001BA239 KN Right: Bottom of cap is twisted – inner mark (1) in line with outer mark. Bottom of cap in correct position – inner mark is under the grip. It is not in line with the outer mark. N N N Place the cap on the opening and rotate it counterclockwise until it engages the filler neck. Continue rotating the cap counterclockwise (about a quarter turn) – this causes the bottom of the cap to be turned to the correct position.
English Checking Chain Lubrication Chain Brake Locking the chain 143BA024 KN If the oil level in the tank does not go down, the reason may be a fault in the oil supply system: Check chain lubrication, clean the oilways, contact your dealer for assistance if necessary STIHL recommends that you have servicing and repair work carried out exclusively by an authorized STIHL servicing dealer. 143BA011 KN The saw chain must always throw off a small amount of oil.
English The chain brake will operate only if the hand guard has not been modified in any way. Releasing the chain brake Winter Operation Check operation of the chain brake Before starting work: Run engine at idle speed, engage the chain brake (push hand guard toward bar nose) and open the throttle wide for no more than 3 seconds – the chain must not rotate. The hand guard must be free from dirt and move freely.
English Heated air is now drawn in from around the cylinder and circulates around the carburetor – this helps prevent carburetor icing. At temperatures above +20 °C N Setting the Master Control Lever Starting / Stopping the Engine To move the Master Control lever from the normal run position (F) to choke closed (l), press down the throttle trigger lockout and squeeze the throttle trigger at the same time and hold them in that position – now set the Master Control lever.
English Fuel pump Between knees or thighs On the ground Press the manual fuel pump bulb several times – even if the bulb is already filled with fuel: – When starting for the first time. – if the fuel tank was run until empty (engine stopped). Holding the Saw N MS 231, MS 231 C, MS 251, MS 251 C Place your saw on the ground. Make sure you have a firm footing – check that the chain is not touching any object or the ground.
English Versions with ErgoStart Cranking WARNING This machine is extremely simple and easy to start, even for children – risk of accidents. 231BA010 KN Do not allow children or other unauthorized persons to attempt to start or otherwise use the machine: – Never leave the machine unattended during work breaks. – After work, store the machine in a safe, secure location. The ErgoStart stores the energy required to start the saw.
English All models When engine begins to fire 4 0 2310BA003 KN 0 1 N Push the hand guard (1) forward – the chain is locked. N Press down the trigger lockout (2) and pull the throttle trigger (3) at the same time. Set Master Control lever (4) to: N Set the Master Control lever (4) to the starting throttle position (n). N Hold and start your saw as described.
English position (n) quickly enough after the engine began to fire, the combustion chamber may be flooded. N Move the Master Control lever to the stop position (0). N Remove the spark plug – see "Spark Plug". N Dry the spark plug. N Crank the engine several times with the starter to clear the combustion chamber. N Refit the spark plug – see "Spark Plug". N Set Master Control lever to the starting throttle position (n) – even if the engine is cold.
English NOTICE Taking Care of the Guide Bar Always slacken off the chain again after finishing work. The chain contracts as it cools down. If it is not slackened off, it can damage the crankshaft and bearings. Picco Rapid Rapid 3/8“ P 5.0 mm 3/8“; 0.325“ 6.0 mm 0.404“ 7.0 mm If the groove is not at least this deep: N Otherwise the drive links will grind against the base of the groove – the bottoms of the cutters and the tie straps will not lie against the bar.
English Shroud Air Filter System The air filter system can be adapted to suit different operating conditions by installing different filters. Changing the filter is quick and simple. Remove shroud N Move the Master Control Lever to the stop position 0 Push the front hand guard forwards – the saw chain is blocked If there is a noticeable loss of engine power. N Fleece filter Removing the air filter N 1 N Remove the shroud (2) Refitting the shroud N 1. HD2 filter 2.
English N Wash the filter in STIHL special cleaner (special accessory) or a clean, non-flammable solution (e.g. warm soapy water). Rinse the filter from the inside outwards under a jet of water – do not use a pressure washer. Installing the air filter Basic information 2. Dry the filter components – do not expose to high temperatures. NOTICE High temperatures and oil can damage the air filter. Filter efficiency can deteriorate as a result.
English Engine stops when idling N Turn the idle speed adjusting screw (LA) clockwise until the saw chain begins to run – then turn it back 2 3/4 turn. Saw chain rotates at idle speed N Turn the idle speed screw (LA) counterclockwise until the saw chain stops turning – then turn another 2 3/4 turns in the same direction WARNING If the saw chain continues to keep rotating in idle even after adjustment, have the chain saw checked by a servicing dealer.
English Checking the Spark Plug If the engine is down on power, difficult to start or runs poorly at idle speed, first check the spark plug. N Fit a new spark plug after about 100 operating hours – or sooner if the electrodes are badly eroded. Install only suppressed spark plugs of the type approved by STIHL – see "Specifications". Removing the spark plug N Remove the shroud – see "Shroud" Installing the spark plug A N Clean dirty spark plug.
English For periods of 3 months or longer N N N Drain and clean the fuel tank in a well ventilated area. Remove chain sprocket cover, saw chain and guide bar. N Dispose of fuel properly in accordance with local environmental requirements. Release chain brake – pull hand guard against the front handle Fit new chain sprocket Remove the saw chain and guide bar, clean them and spray with corrosion inhibiting oil.
English N N After refitting, turn the clutch drum and/or spur chain sprocket approx.
English File holder Proper sharpening N Select sharpening tools in accordance with chain pitch N Clamp guide bar if necessary N 689BA025 KN Block saw chain – push the hand guard forward N Always use a file holder (special accessory, see table "Sharpening tools") when sharpening saw chains by hand. File holders have markings for the sharpening angle. To advance the saw chain, pull the hand guard toward the handlebar: The chain brake is disengaged.
English N File only from the inside outward N The file only sharpens on the forward stroke – lift the file on the backstroke Do not file tie straps and drive links N Rotate the file a little periodically in order to avoid uneven wear N To remove file burr, use a piece of hardwood N Check angle with file gauge All cutters must be equally long. With varying cutter lengths, the cutter heights also vary and cause rough running of the saw chain and chain breakage.
English WARNING N After sharpening, clean the saw chain thoroughly, removing any filings or grinding dust – lubricate the saw chain thoroughly N In the event of extended periods of disuse, store saw chains in cleaned and oiled condition 689BA052 KN Depth gauges that are too low increase the kickback tendency of the chain saw.
English Complete machine Visual inspection (condition, leaks) Manual fuel pump (if present) Fuel pick-up body / filter in fuel tank X Clean Function test X X X X X Have checked by dealer check X Have repaired by a specialist dealer1) X check X Clean, replace filter insert X X X Fuel tank Clean X Lubricating oil tank Clean X Chain lubrication check X Check, pay attention to sharpness X X Checking the chain tension X X X sharpen Check (wear, damage) Guide bar X X X repla
Anti-vibration elements check X Clean X Check idle adjustment – saw chain must not rotate X Chain catcher Safety information label As required If damaged If faulty X X X X Set the idle speed; if required have the chainsaw repaired by a specialist dealer1) X Adjust electrode gap X Replace after 100 hours of operation Tighten2) X Have checked by dealer1) Spark arresting screen in muffler Annually X Clean Accessible screws and nuts (except adjusting screws) Monthly X Cylinder fins S
English Main Parts 1 2 3 4 13 7 14 5 6 7 8 9 10 11 12 13 3 2 1 # 4 5 10 6 11 9 7 14 12 15 16 17 18 19 20 21 22 23 24 25 26 # 8 18 17 1 20 16 19 1 22 24 25 23 26 2310BA029 ST 15 21 1) MS 231, MS 231 C, MS 251, MS 251 C Shroud lock Carburetor adjusting screws Fuel pump1) Shutter (summer and winter operation) Chain brake Chain sprocket Chain sprocket cover Chain catcher Side chain tensioner1) Spiked bumper Guide bar Oilomatic chain Adjusting wheel1) (quick chain adjuster) Handle of wi
English Fuel tank capacity: Specifications 390 cc (0.39 l) Chain Lubrication Engine STIHL single cylinder two-stroke engine Oil tank capacity: MS 231, MS 231 C Displacement: Bore: Stroke: Engine power to ISO 7293: Idle speed:1) 42.6 cc 42.5 mm 30 mm 2.0 kW (2.7 bhp) at 10,000 rpm 2,800 rpm MS 251, MS 251 C Displacement: Bore: Stroke: Engine power to ISO 7293: Idle speed:1) 1) Fully automatic, speed-controlled oil pump with rotary piston 45.6 cc 44 mm 30 mm 2.2 kW (3.
English Sound power level Lw to ISO 22868 MS 231: MS 231 C: MS 251: MS 251 C: 114 dB(A) 114 dB(A) 114 dB(A) 114 dB(A) Vibration measurement ahv, eq to ISO 22867 MS 231: MS 231 C: MS 251: MS 251 C: Handle, Handle, left right 3.9 m/s2 3.9 m/s2 2 3.9 m/s 3.9 m/s2 2 3.9 m/s 3.9 m/s2 3.9 m/s2 3.9 m/s2 The K-factor in accordance with Directive 2006/42/EC is 2.0 dB(A) for the sound pressure level and sound power level; the K-factor in accordance with Directive 2006/42/EC is 2.0 m/s2 for the vibration level.
English Users of this machine may only carry out the maintenance and service work described in this user manual. All other repairs must be carried out by a servicing dealer. STIHL recommends that you have servicing and repair work carried out exclusively by an authorized STIHL servicing dealer. STIHL dealers are regularly given the opportunity to attend training courses and are supplied with the necessary technical information.
English Guaranteed sound power level all versions of MS 231: 116 dB(A) all versions of MS 251: 116 dB(A) The EC type examination was carried out by DPLF Deutsche Prüf- und Zertifizierungsstelle für Land- und Forsttechnik (NB 0363) Max-Eyth-Weg 1 D-64823 Gross-Umstadt Certification No. all versions of MS 231: all versions of MS 251: K-EG-2010/5603 K-EG-2010/5605 Technical documents deposited at: ANDREAS STIHL AG & Co.
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