Stihl MS 261 C-M service schedule

1. Remove the shroud. Pull off the plug boot and clean around the plug.
2. Push the combination spanner through the grommet onto the plug and unscrew it.
3. Set the new plug's gap to 0.5 mm.
4. Screw it in by hand through the grommet, then tighten. Fit the boot and press it down firmly.
5. The plug must have its adapter nut fitted and tight; a loose nut can arc and start a fire.
6. A sooty plug points to too much oil in the mix, a dirty air filter or poor running conditions. Put the cause right.

Tools: Stihl combination spanner, Feeler gauge 0.5 mm

1. Stihl says do this weekly. Engine off, chain brake on, gloves on.
2. Remove the sprocket cover, chain and bar.
3. Clean the oil inlet hole, the oil outlet channel and the bar groove.
4. File off any burrs on the bar rails.
5. Measure the groove depth with the gauge on the file gauge where the bar is most worn. For .325 in Rapid chain the minimum is 6.0 mm. Replace the bar if it is shallower.
6. Refit the bar the other way up (flip it), refit and tension the chain.

Tools: Flat file, Stihl file gauge (has a groove depth scale), Work gloves, Rag

1. Stihl says check weekly. Engine off, gloves on.
2. Remove the sprocket cover, chain and bar. Pull the hand guard back to release the chain brake.
3. Check the wear marks on the sprocket. Replace it if they are deeper than 0.5 mm, or after two chains have been worn out.
4. To replace: prise off the E-clip, take off the washer and rim sprocket. Check the splines on the clutch drum; if badly worn, the drum should be replaced too.
5. Pull off the clutch drum and needle cage, clean the crankshaft stub and needle cage and grease them with Stihl grease.
6. Refit the needle cage and drum, and turn the drum about one full turn so the oil pump drive engages.
7. Fit the rim sprocket with its cavities facing outwards, then the washer and E-clip.
8. Use a genuine Stihl sprocket so the chain brake works properly.

Tools: Combination spanner, Small screwdriver (E-clip), Stihl sprocket wear gauge (special accessory), Work gloves

1. Monthly: drain and clean the fuel tank and the chain oil tank so dirt does not reach the pumps.
2. Before work: hold the running saw over a light surface; the chain must throw off a film of oil.
3. If the oil tank is still part full when the fuel runs out, check the bar oil holes and the oil supply, and see a dealer if needed.
4. The oil flow screw (underneath, where fitted) has an Ematic position E for medium flow. Turn clockwise for more oil and anticlockwise for less. The chain must always be wet with oil.
5. Never use waste oil: it lacks lubricating properties and can cause skin cancer.

Tools: Approved fuel can, Clean rag, Screwdriver for the oil flow screw

1. Engine off and cool.
2. Brush the air intake slots on the fan housing clean (Stihl: weekly).
3. Remove the shroud and brush the cylinder fins clean (Stihl: monthly).
4. Refit the shroud.

Tools: Soft brush, Combination spanner

1. Wear full chainsaw PPE for this test: helmet, eye protection to EN 166 or a face shield, ear defenders, gloves, trousers with cut-retardant pads and safety boots with cut-retardant material and steel toe caps.
2. Before work and at every refill: start the saw on firm ground with the chain clear of the ground, and let it idle.
3. Push the front hand guard towards the bar nose to engage the brake. Open the throttle wide for no more than 3 seconds. The chain must not move.
4. Release the throttle, then pull the hand guard back towards the front handle until it clicks to release the brake.
5. Keep the hand guard free of dirt so it moves freely. Never modify the hand guard; the brake only works if it is unaltered.
6. Do not run the engine at high revs with the brake on: it quickly damages the clutch and brake.
7. If the chain moves during the test, stop using the saw and take it to a Stihl dealer.
8. Book the dealer brake service: every 3 months (full-time use), 6 months (part-time) or 12 months (occasional).

Tools: Chainsaw PPE (helmet, visor or goggles, ear defenders, saw gloves, chainsaw trousers, chainsaw boots)

1. Work outdoors, away from flames. Avoid skin contact with petrol and its fumes.
2. Empty the fuel tank into an approved can.
3. Pull the pickup body out of the filler neck with a hook. Do not stretch or tear the fuel hose.
4. Fit the new pickup body to the hose and push it back into the tank.
5. Refuel with fresh 50:1 mix and check for leaks before starting.

Tools: Wire hook to pull the pickup out of the tank, Approved fuel can, Gloves

1. Wear work gloves: the cutters are sharp even when the saw is off.
2. Clamp the bar. Push the hand guard forward to lock the chain; pull it back to release the brake when you need to move the chain on.
3. Clean the chain and check it for cracks and damaged rivets. Replace damaged parts.
4. File with a 4.8 mm round file in a file holder. Hold the file level, at right angles to the bar, at the 30° angle marked on the holder (Rapid Micro and Rapid Super chains; ripping chains marked X use 10°).
5. File from the inside of the cutter outwards, only on the forward stroke. Two or three strokes are usually enough. Do not file the tie straps or drive links.
6. Keep all cutters the same length: file them all down to the shortest one. Uneven cutters cause rough running and chain breakage.
7. Check the depth gauges with the file gauge after every sharpening. For .325 in chain the gap between depth gauge and cutting edge is 0.65 mm. If the gauge stands above the file gauge, file it flush with the flat file, then round off its front edge parallel to the service mark.
8. Never file the rest of a humped drive link and never take depth gauges lower than specified: it increases kickback.
9. Clean off filings and oil the chain well afterwards. Store spare chains clean and oiled.

Tools: Bench vice or stump vice for the bar, Work gloves, Piece of hardwood to remove file burrs

1. Remove the shroud: move the Master Control to STOP, push the hand guard forward, and turn the twist locks a quarter turn anticlockwise.
2. Brush loose dirt away from around the filter.
3. Turn the filter a quarter turn anticlockwise and lift it out towards the rear handle. Do not use tools on it.
4. Knock out the dirt, spray the outside with Stihl special cleaner or soapy water and rinse the outside under warm running water.
5. Let it dry naturally: no heat, and never oil the filter. Replace a damaged filter.
6. Refit: push it into the housing and turn clockwise until it locks, with the STIHL name horizontal. Refit the shroud.

Tools: Combination spanner (shroud twist locks), Stihl special cleaner or soapy water, Soft brush

1. Look at the rubber/spring mounts between engine and handles for cracks, splits or looseness.
2. If the handles feel spongy or vibration has increased, have the elements replaced by a Stihl dealer.

1. Before work, check the catcher under the bar is present, undamaged and secure.
2. If it is damaged or missing, fit a new one before using the saw.

Tools: Screwdriver (Torx/spline)

1. Before work: let the engine idle with the chain brake released and the chain clear of everything. The chain must not move.
2. If the chain moves at idle, stop and take the saw to a Stihl dealer. There is no owner idle screw on this model.
3. If running is poor after a change of fuel or conditions: on M-Tronic version 3.0 or later (shown on the approval label), calibrate as the manual says: Master Control to the start position, chain brake on, start without touching the throttle and let it run 30 to 60 seconds, release the brake, then hold full throttle for at least 30 seconds until the speed drops.
4. On M-Tronic below version 3.0, make five even full-throttle cuts to speed up the automatic adaptation.
5. The chain turns during calibration: hold the saw properly and keep clear of the chain. If the engine keeps stopping, put the brake on and see a dealer.

Tools: Chainsaw PPE

1. In a well-ventilated place, drain and clean the fuel tank. Dispose of the fuel properly.
2. Run the engine until the carburettor is dry, so the diaphragms do not stick.
3. Take off the chain and bar, clean them and spray with corrosion-inhibiting oil.
4. Clean the saw thoroughly, especially the cylinder fins and air filter.
5. If you use a bio chain oil such as BioPlus, fill the chain oil tank completely.
6. Store dry, high up or locked away from children.

Tools: Approved fuel can, Corrosion-inhibiting oil, Brush