STIHL MS170–MS271 fuel, chain and service differences

The two smallest STIHL homeowner saws

The STIHL MS 170 is a 30.1 cc single-cylinder two-stroke rated 1.3 kW (1.8 hp), and the MS 180 is a 31.8 cc saw rated 1.5 kW (2.0 hp). The C versions add a quick chain tensioner and the ErgoStart easy-pull starter. All idle at 2,800 RPM, weigh about 3.9 kg (4.2 kg for the C) without a bar and chain, and take the same plug, tanks and chain.

STIHL says to pour the oil into an approved safety fuel canister first, then add the gasoline and mix until the oil is dispersed. It also sells MotoMix, which is premixed with HP Ultra oil. Refill the chain oil tank every time you refuel, and where you use a biological chain oil such as STIHL BioPlus, fill the tank completely before storage.

The maintenance chart

STIHL says to shorten the intervals in dusty conditions or with resinous wood.

Parts to buy for the STIHL MS 170 and MS 180 chainsaws

The kit numbers for every STIHL saw, trimmer and blower are on the STIHL service kit page.

How the MS 170 and MS 180 differ

VersusGuy lists the MS 170 as a 30.1 cc engine producing 1.6 kW (2.2 hp) and describes the MS 180 as noticeably more powerful, and its companion comparison notes the weight is identical.

Because the two share a frame and service parts, the fuel mix, plug and filter information here applies to both saws. The real choice is between the MS 170's lower price and the MS 180's extra power for the same weight.

When to use cold start, warm start and run on an MS 170 or MS 180

The STIHL manual for the MS 170 and MS 180 ties the master control lever position to what the engine just did. Cold start is for a cold engine, for when the engine stalls as you open the throttle after starting, and when the fuel tank has run empty.

Warm start is for an engine that has been running for about a minute, after the engine has fired for the first time, and after ventilating the combustion chamber if the engine was flooded. From warm start the lever returns to run when you squeeze the throttle trigger.

To move from run to cold start, hold the throttle trigger lockout and the trigger together and set the lever. Warm start can be selected only from cold start. Stop 0 switches the ignition off.

The manual describes two ways to hold the saw while starting, both with it placed securely on the ground, the chain clear of everything, the left hand on the handlebar with the thumb wrapped around it, and the right foot in the rear handle.

Chain brake service interval and the 3 second test for the MS 170 and MS 180

Before starting work, the manual says to run the engine at idle, engage the chain brake by pushing the hand guard toward the bar nose, and open the throttle wide for no more than three seconds. The chain must not rotate, and the hand guard must be free of dirt and move easily. It says the brake wears in normal use and should be serviced by trained personnel, ideally an authorized STIHL dealer, quarterly for full-time use, every six months for part-time use and annually for occasional use.

It also says the inertia of the front hand guard can trigger the brake in a kickback even if your left hand is not behind the guard, as in a felling cut, but only if the hand guard has not been modified. Releasing the brake by pulling the guard back is required before opening the throttle, because running the engine at high revs with the chain locked will quickly damage the engine and the clutch and brake.

MS 170 versus MS 180 in STIHL's specifications

The two saws differ mainly in engine size. The MS 170 is 30.1 cm³ with a 37 mm bore and 28 mm stroke, rated 1.3 kW (1.8 hp) at 8,500 RPM. The MS 180 is 31.8 cm³ with a 38 mm bore and the same stroke, rated 1.5 kW (2.0 hp) at 9,000 RPM.

Both idle at 2,800 RPM and use a Bosch WSR 6 F, NGK BPMR 7 A or STIHL ZK C 14 plug with a 0.5 mm gap.

Both hold 250 cm³ of fuel and 145 cm³ of chain oil, which a fully automatic speed-controlled pump delivers. Dry weight without the cutting attachment is 3.9 kg for the MS 170 and MS 180, and 4.2 kg for the MS 170 C with ErgoStart and the MS 180 C with quick chain tensioner and ErgoStart. For the carburetor, the standard setting is the idle speed screw (LD) turned counterclockwise until it seats firmly, then two turns clockwise.

MS 170 and MS 180 bars, chains, noise and vibration in STIHL's data

The manual lists Rollomatic guide bars in 30, 35 and 40 cm lengths with a 3/8 inch P pitch for both saws. The MS 170 takes the 1.1 mm groove width and its listed chain is the 3/8 inch P Picco Micro Mini 3 (61 PMM3, type 3610) with a 1.1 mm drive link gauge.

The MS 180 lists both 1.1 mm and 1.3 mm grooves, and adds the Picco Micro 3 (63 PM3, type 3636) and Picco Duro 3 (63 PD3, type 3612) chains at 1.3 mm gauge. Both use a 6-tooth sprocket for 3/8 inch P chain, and the manual quotes a maximum chain speed of 21.1 m/s for the MS 170 and 22.3 m/s for the MS 180.

The noise and vibration tables separate the two saws. Sound pressure is 98 dB(A) for all four versions, and sound power is 107 dB(A) for the MS 170 and 108 dB(A) for the MS 180. Vibration at the handles is 4.2 m/s² left and 5.9 m/s² right for the MS 170, and 6.6 and 7.8 for the MS 180, with the MS 180 C at 7.6 and 7.4, each with a 2.0 K-factor.

The figures are STIHL's own, and the difference between the two saws is largest at the handles.

In countries where the muffler carries a spark arresting screen, the manual says never to run the saw without it or with it damaged, to clean or replace it if it is dirty or heavily carbonized, and to fit new muffler plugs if any are missing. It says to check the screen first if the engine is down on power, and to fit a new spark plug after about 100 operating hours or sooner if the electrodes are badly eroded.

Sharpening the MS 170 and MS 180 chain: file size and part numbers

STIHL's sharpening tools table matches the file to the chain pitch, and the 3/8 inch P chain on these saws takes a 4.0 mm (5/32 inch) round file, part 5605 772 4006. The table pairs it with file holder 5605 750 4327, file gauge 1110 893 4000, taper square file 0814 252 3356 and a complete sharpening set, 5605 007 1027. STIHL chains are sharpened at a 30° angle, and the manual says that compliance with the listed angles and dimensions is absolutely necessary, because an improperly sharpened chain, especially with depth gauges that are too low, can increase kickback tendency.

It also gives a replacement rule for the chain sprocket. Replace it after two saw chains, or earlier if the wear marks are deeper than 0.5 mm, otherwise the chain's service life is reduced, and it says that using two chains in alternation helps preserve the sprocket. STIHL recommends original chain sprockets to keep the chain brake working as designed, and says carbide-tipped Duro chains are best sharpened by a servicing dealer.

Three STIHL saws, one mix and one plug

The STIHL MS 210, MS 230 and MS 250 share one instruction manual. They are single-cylinder two-stroke saws of 35.2, 40.2 and 45.4 cubic centimeters, rated at 1.6 kW (2.2 hp), 2.0 kW (2.7 hp) and 2.3 kW (3.1 hp). All three use the same 1:50 fuel mix, the same spark plug and gap, and the same 470 cubic centimeter fuel tank and 200 cubic centimeter chain oil tank.

At 1:50 the manual’s mixing examples are 20 millilitres of oil per liter of gasoline, 100 for 5 liters and 200 for 10 liters. Pour the oil into an approved safety canister first, then add the gasoline. Mixed fuel should not be stored for more than 30 days; mix only what you will use in a few weeks.

STIHL says gasoline with more than 10% alcohol should not be used in engines with manually adjustable carburetors.

Air filter, spark plug and chain oil

The maintenance chart

Parts to buy for the STIHL MS 210, MS 230 and MS 250 chain saws

The kit numbers for every STIHL saw, trimmer and blower are on the STIHL service kit page.

A 50 cc two-stroke: two tanks, one plug, one filter kit

The STIHL MS 271 is a 50.2 cc (3.06 cubic inch) single-cylinder two-stroke chainsaw rated at 3.5 hp, with an idle speed of 2,800 RPM and a maximum speed with cutting attachment of 13,000 RPM. Like the Echo and the Husqvarna on this site it has no crankcase oil to change. It runs on mixed fuel, and it has a separate tank of chain oil that a pump feeds to the bar.

The filter parts: one service kit

STIHL sells a chainsaw service kit that fits the MS 271, MS 291, MS 311 and MS 391. STIHL USA’s part number for it is 1141 007 1800, and the page says it holds an air filter, a fuel filter and a spark plug. STIHL notes the MS 311 must have a serial number greater than 295938526 for that kit.

The manual confirms the two parts the kit replaces on a schedule: the fuel pick-up filter in the tank, which it says to clean or replace, and the air filter, which it says to clean and replace.

One thing to know about the plug. STIHL’s manual gives the gap as 0.5 mm. NGK’s catalog page for the MS 271 lists the BPMR7A with a 0.7 mm gap.

Set the plug with a gauge to the manual’s 0.5 mm.

The maintenance chart

STIHL says to shorten the intervals in dusty conditions or with resinous wood, and to tighten the cylinder block screws after 10 to 20 hours the first time a professional saw is used.

Parts to buy for the STIHL MS 271 chainsaw

The same kit numbers are on the STIHL service kit page.

Who the MS 271 Farm Boss is built for

SawOff's review describes the MS 271 as a mid-range saw for landowners and farmers powered by a 50.2 cc 2-MIX engine, and another review places it as substantial power for homeowners without the complexity of a professional-grade saw.

That positioning is why its service kit (filters, plug, fuel filter) is worth stocking: a saw used for seasonal firewood cutting accumulates hours quickly in autumn, and the air filter is the part that clogs first in dusty cutting.

Starting, the chain brake and carburetor limits on an MS 271

The STIHL manual for the MS 271 and MS 291 explains the master control lever in detail. From run you move it to cold start by holding the throttle trigger lockout and the throttle trigger together.

Warm start can only be reached from cold start, and blipping the throttle while pressing the lockout makes the lever jump from warm start to run. Stop is position 0.

Its warning about the chain brake is blunt: release it before opening the throttle, because running the engine at high revs with the chain locked quickly damages the engine and the clutch and brake.

Every new chain needs a 2 to 3 minute run-in, after which you recheck tension. The saw chain must always spin off a small amount of oil, and STIHL says never to run the saw without chain lubrication because a dry chain can be damaged beyond repair very quickly. The inertia of the front hand guard can also trigger the brake if kickback force is high enough, but only if the hand guard has not been modified.

MS 271 carburetor, air filter and storage in the manual

The carburetor leaves the factory on a standard setting. To return to it, turn the high speed screw (H) counterclockwise as far as it goes, at most 3/4 of a turn, then turn the low speed screw (L) clockwise as far as it goes and back 1/4 turn. Whenever L is adjusted, the idle speed screw (LA) usually needs readjusting too.

For unsatisfactory performance at altitude, the manual says to make the standard setting, warm the engine, and turn H slightly clockwise, which leans it, but no further than the stop.

The air filter is a fleece element. STIHL says to knock it out or blow it clear from the inside outward, and if that is not enough, to wash it in warm soapy water or STIHL special cleaner, rinse it inside out under a jet of water without a pressure washer, let it dry with no external heat, and not to impregnate it with oil.

For storage of about 30 days or longer, it says to drain and clean the fuel tank in a ventilated area, press the manual fuel pump at least five times if fitted, and run the engine at idle until it stops. Then remove the chain and bar, clean them and spray them with protective oil, clean the machine with attention to the cylinder fins and air filter, and store it dry and out of reach of children. If you use biological chain oil, fill the oil tank before storing.