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Stihl MS 390 / MS 391 Farm Boss

Stihl MS 390 / MS 391 Farm Boss

391 FarmBoss and MS 390
3.6 from 28 reviews


Don't buy Stihl , I bought a stihl MS250 for $695 and motor died after 4 months ( or 10 medium tress cuts) . Stihl dealer said we didnt mixed enough oil and refused to pay the repair motor cost of $475, But we always mixed 100 per 5L. We bought the MS391 while we waiting for the dispute. Buy after few days use, the MS391 wont stop now we have to bring it back to repair. SO DO NOT buy STIHL produsts, waste time
Annie from New Zealand

Purchased for $1,295.00.

Build Quality
Value for Money
Ease of Use
Cleaning & Maintenance

don't buy 391, no back up and Stihl blame operator

I have owned many chainsaws over last 25 years through our hardwood timber biz, recently bought 3 units 391 and 1st unit lasted 4 weeks when compression died and can see a hole in piston after spark plug removed. all 3 units are not working with same problem, usage is moderate and maintained. enough power but no reliability and Stihl will not support unless we pay money to repair. very poor form. Careful what you buy and as newer Stihl saws too many electrics and lighter wight, not as robust. using my 20 year old 268 Husky rather than 391 with latest features but no performance. by the way my 18 month old 381 is running well!!

Date PurchasedMay 2018

Fantastic saw

Owned my 390 since 2008 it’s always started and cut over 100 ton of hardwood , jarra, stringy bark yellow box iron wood black wood white gum
It’s always started you have to follow the procedure
Choke on pull till it has the first fire then flick the choke to fast idle put chain break on then it starts flick the accelerator and it idles
I always clean the air filter and measure my oil with a measuring cup to 5 litres of petrol
After use I always take the bar off and clean with compressed air I run a file across the teeth at 30-35 degrees to sharpen only 2 passes needed
I've never taken it in to a dealer iv changed the plug once in 10 years
I just cut 10 ton of wood this week thought how good this saw is !!!

Date PurchasedJun 2008

Good saw if only it would run all the time (2)

Follow up to my last review where I could not get the saw to run. There is a specific starting procedure that makes it run. First, pull the trigger all the way, then flip the choke lever to full choke. Pull the starter cord 3 times, not 4 times, and not 2 times, 3 times only, then flip the choke to half choke and pull away, it should start with in the first 2 or 3 pulls. If this doesn't work, it is flooded, and you need to pull the spark plug, spin it over to get rid of the gas and start the procedure over.
Still cuts amazingly well once it gets going.

January 6th 2019 Update: Good saw if only it would run all the time (2)

January 2019 Third follow up to my review over the summer of 2018. I still have the same saw. The local dealer got sick of seeing me because shortly after following my exact starting procedure, I could not get it to start again. After they spoke to Stihl and got no help, the dealer swapped the entire ignition module out. Although it is still a little touchy to start, it is well with in what I would expect from a reasonable chain saw.
The previous sequence I listed with certain number of pulls etc. really had nothing to do with anything.
Put on the choke, pull a few times, it may or may not start. Flip to half choke and pull until it starts. When it's cold, this should be a few pulls but you should see some light smoke or hear it trying to start and then it does.
My saw now runs great and cuts amazingly. It is a heavy saw, so this makes it great if you are bucking up pieces of wood already on the ground. It's not so great for overhead branch trimming work. I am a 53 yr old carpenter in very good health.

Date PurchasedApr 2018

Good when going but hard to start and died early

Bought the farm boss to cut blanks for turning and slab cutting for furniture. Had a fair bit of work clearing fallen trees after recent cyclone and some cuts of a full tank at a time doing slabs. After 11 months and about 20 hrs work it upped and died. Always used 40 to 1 mix but it had lost power and stopped 10 min into a slab cut,never to go again. Dealer says I cooked it but I would expect it to cope with long cuts at high revs. No fouling of air vents or other contributing factors. Starting always a bit of an issue. Never less than 6-8 pulls and often flooded and needed a rest

Date PurchasedJul 2017

Great chsinsaw

Husband very happy, wish we had bought one 20 years ago. Slices through sugar gum like butter, makes the job so much easier. Light to hold and to maneuvers. Received a free chain with it , so wuite a bargain. Wishes he hasn't wasted his time with inferior brands & got one of these years ago

Date PurchasedJun 2018

Stihl - Excellent chainsaws

We bought two of these saws. Used both for cutting wood all day long. Sharpen one while the one one is cutting. Used a 20" blade for low down torque. Excellent saws. Had them for years now and never let us down. Yes they can be a bit temperamental, but what chainsaws don't? Far better than any other brand I've owed. Crushed oleo-mac it was that bad... Great saws, still have them. For those who don't know how to start them, push the fuel primer six times, then pull the choke and pull start until it wants to start. Then push it back in and pull start. It should start every time like this. Had these saws for many years now and very seldom had an issue if you follow this procedure given by dealer.

Date PurchasedApr 2003

wish I would have never bought it!

Really hard to start in any weather. Floods fast. Like Luke said, "shop shelf decoration". some tell you to pull it ounce on full choke, ounce on half choke, then switch to run, and it will start. Wrong! Others say, pull on full choke till fake start, then on half, at witch point it will start. then release the trigger back to idle. Wrong!
No wonder they discontinued it. Also went through an ignition coil before it had 50 hours on it.

Date PurchasedJan 2014

Muffler keeps coming loose

The saw works great but the 2 bolts keep backing out on the muffler. I tried putting lock tight on the bolts but that didn't work either. I'm taking it back to the dealer to see what the problem is. I own 3 other Stihl saws have never had a problem. I think this is a design flaw my other saws have all thred bolts with nuts on the muffler this saw has bolts that go into a small hole in the muffler that are very hard to get to.

Date PurchasedApr 2017


Crap chainsaw wouldn't start dealer said wrong fuel mix I said you told me 50/1 . Other 2 chainsaws still going on same fuel mix . They can fix it for $800 wow only used it 6 times .be careful when buying Stihl chainsaws and whatever they say don't use 50/1 mix asking for trouble

Date PurchasedOct 2016

15 minute saw

Bought MS391. Dealer prepped and started. Oil in, proper dealer sourced ethanol free premix. Saw blew hole in piston within 15 minutes of normal operation (not under excessive load). Dealer dismantled and consulted with regional Stihl warranty representative. 6 weeks later I call to relate story. I am told I pushed it too hard, i.e., my fault. Unbelievable! I have used an MS170 with same fuel, on same logs with same method ripping 600 lineal feet t/- with no problem and still running strong. This big new saw did not last 4 feet. Stihl wants me to pay for the labor of repair. Out $629.00, six weeks of down time and anticipating using a saw I have no confidence in after paying extra labor cost I should not owe. Poor business practice. Way to loose customers. Shelf decoration for shop, but not a chainsaw that cuts wood.

Date PurchasedApr 2017


I brought a 391 for general wood cutting. It was used 6 times with each time being less then .45mins max.
Blew a hole in the piston. Stihl blamed the fuel, all saws were run off the same fuel that day.
Dealer would not warrant the saw was less then 9 month old or would head office on dealers recommendation.
Had an independent replace piston, same thing happened fuel tested and all good. Looks like when warm it developed an air leak.
I have a lot of stihl products including a mini boss which has done a lot of work and has never fail.
Would not trust stihl or their products after dealing with them over this issue.

June 26th 2017 Update: Blowing pistons

Blew piston fuel was good. Suggested air leak but was told I was overloading the saw. Was cutting rounds 150mm - 250mm for meters stove. Only used 6 times chains always sharp. Still wouldn't warrant.
Replaced piston same thing happened independent mechanic found an air leak in crank case when heated up.

Date PurchasedJun 2016

bought a391 stilh

i just bought a391 second hand from Gumtree ,2 months old . have used these before,great saw i need a bit more grunt than my 311 to cut red gum. cutting another load of redgum on Sunday. Will see how it performs against my 311 in performance ... like i say look after them ,they will last along time.

May 8th 2017 Update: chainsaw

l just came back from ballarat with a trail of red gum.l used my 391 stihl ,it performed like a dream. Going back Friday for another load , people who have trouble with the saw STOP complaining about them , l have 2 saws now,311,@391, both working perfect,if you have trouble ,take it back and ask them how to start them ,the whey they do it , l have no trouble with my dealers in geelong ,they are very helpful giving advice , no harm in asking them ,clean your saws after each use ,they wont let you down. Ron

Date PurchasedMar 2017

Chain bar does not stay in place, chains by Stihl do not last. Worst problems I have ever had

Stihl has two bolts that take two nuts supposed to hold the bar in place to enable holding the chain taught on the bar. The system does not work. I can cut just a small amount of brush, or a tree and the chain loosens and until I figured out the cause of this spanking new chain saw, the chain came off the bar several times. I feel cheated by the Manufacturer for building such a poor product.

Date PurchasedMay 2016

Bad gas - my...

Bought my first Stihl saw today, an MS391 with a 25" bar. The dealer sold me 3 additional chains and synthetic oil for the fuel mix, put chain oil and gas in it, and I was on my merry way.
On the way home I bought a new gas can, topped my truck up with ethanol free regular and filled the new can after having poured one container of oil in it.
At home I started it up following the handbook, and decided to "practice" on some walnut (got a big oak to work on!). After half a tank, it was tired and bogged down on 4" stuff, and after 3/4 tank it stopped.
I decided to fill it up with my new gas, when I noticed, that the stuff that was in the tank was clear, without any sign of dye from oil.
It started up with lots of tries, but only ran for two secs or less.
I brought it back and told the sales guy, that maybe the service guy put straight gas in it instead of mix.
They tinkered with it, replaced the fuel filter and then told me, that I had simply used old gas, and that they could clearly smell it.
- That's when I got agitated and I told the sales guy, that I think they ruined it from the start and I wanted a replacement.
I was told, the MS391 is a rare model, and they'd have to order one, which might take a couple weeks.
I said, I am not taking the one they sold me back.
They found a replacement power head in 30 seconds - oy!
When they handed it to me with my used bar n chain as well as cover plate, I asked them if they had put gas in it.
"Of course" was the reply, and I made them dump it - didn't want #2 be conking out also.
Sofar, it's no better than my six year old 33cc Poulan, which should tell the reader something.
Disgusted with dealer, dubious mechanic, and lies ("got to order one..."), as well as underwhelming performance.
I hope, this one "wakes up" and will actually work.
I'll see.

Date PurchasedApr 2017

Awesome saw

This is my first chainsaw and have owned it now for 5 years.
Only problem has happened recently when the clutch drum E-clip broke without me knowing and hence the retainer clips on the clutch have broken as well. Easy to fix myself with getting the parts from the local Stihl shop.

Date PurchasedMay 2011

Great saw compared to others I owned.

I use my 391 about once a year. I bought it because I was tired of performing three hours of work on my old saw just to use it for 30 minutes. The 391 with 25" chain is great...a bit hard to start though.... Has hurt my arm a few times especially when it kicks.....ouch. One problem I have had performance wise is saw dust... Keep the blade sharp, it does not like dust...i have had the clutch lock up three times because of dust...a quick cleaning puts it back in operation... But that heart sinking feeling when it won't start killed me.... Yup feels like a locked up piston but it's just saw dust in the clutch area.... Clean it up and press on....sharpen that chain to reduce dust.

Date PurchasedNov 2012

This is Stihl at their best.

The MS391 (and the Husky 365 Special) - best saw/s I've ever owned and I've owned a lot as its my livelihood. I got mine secondhand for $350 from a pawnbroker and I didn't realize at the time what a steal I was getting. It had been reduced from $500. I tested it out on the pavement and could tell it wasn't oiling. I wondered should I take a gamble, it might just be blocked holes on the bar. Luckily I made the decision to buy it anyway. It wasn't the bar sadly. After losing several hours figuring out how to find the oil pump, and knowing that it may actually be blocked oil filter, crack in oil line or worn out worm gear instead, a quick phone call to Stihl and a quote of $145 for an oil pump prompted a search on a little known site called ebay and a $35 pump and $15 worm gear arrived 3 weeks later from HK. Once the parts were replaced it oiled beautifully for 2 more years up until recently when the Stihl shop correctly diagnosed that the crankshaft is worn out. It had a hard life as an aborist's saw prior to my eucalyptus work. So now the clutch drum rotates clumsily and doesn't pick up the worm gear which drives the cog on the oil pump. So no oil feed any longer :( So I'm using it by dipping the tip of the bar in a drum of used sump oil every time I release the throttle, keeping it lubricated. Very messy! Meanwhile I um and er about spending $1350 on a new one or trying an echo instead.

As for RICCEY above, I would be very skeptical of a workshop telling you you've stuffed your piston unless you yourself can verify the saw has completely seized up when you pull the cord, especially if they also sell new chainsaws. I had 2 workshops look at my MS391 and they were correct in saying that the crankshaft is worn out and its such a big, expensive job, it's not worth fixing ($392 for crankshaft alone) but they both said the piston and cylinder were shot. The thing still has compression as good as a new saw and it fires/pops on choke first pull and starts second pull with choke off. I would hold YOUR saw 4 feet off the ground by the pull cord alone and see if it holds up or quickly falls to the ground. Mine still holds up = great compression. It still requires Schwarzenegger to start it! But if YOUR cord pulls the flywheel over really easy the piston may be on its way out, but it will still cut wood effortlessly compared to most new saws on the market. I found this saw is really powerful. I was surprised to see it was only 64cc , 3.3KW, it feels more an over 70cc saw to me.

As for what you've said about your fuel mixture... I've been told by a chainsaw mechanic any saw, including this one can run safely at 50:1 no matter what brand 2 stroke oil used. I've always struggled with this issue as if you go stingy on the oil, you could end up paying so much more in the long run on a new saw if it does seize up. My dad has always had distrust of manufacturer's recommendations and will only use 25:1, so I did too for many years, but eventually wanted to reduce the amount of smoke I was inhaling and money spent on oil so now I meet the half way point between Stihl's recommendation of 50:1 with Stihl 2-stroke oil and dad's belief of 25:1 being the safe limit. I use 150ml oil per 5 litres of petrol (37.5:1 technically) and this works well for me. If you take your muffler off and pull the cord to move the piston up inside the cylinder, look for heavy 'scoring' on the piston (scratches). Mine has plenty of scoring but it's not the end of the saw's life if it still has good compression as stated above.
Also, if you really clean the air filter out every tank load of fuel I would think your cylinder would be in excellent condition. I know of people who don't ever clean the air filter cos they didn't know you had to!! I probably clean air filters every 4 or 5 tank loads of fuel. The good thing about these saws is they have 2 parts to the air filter which is sort of like having 2 in a row. A Stihl shop told me you only need to clean it once every 6 months, but I think this is bad advice unless you only use the saw a few times a year. Blow it out with an air compressor and/or wipe with a brush and petrol.
My saw also went through a phase where it just decided it wouldn't start. I did the usual stuff like replace spark plug, check spark, clean air filter and blow out crud around carby but it didn't make a difference. I gave it to a 'backyard' mechanic and I don't know what he did to it but it hasn't given me much grief since.

I love cutting with the grain with this saw (ie. what you'd normally use a splitter for) with a newly sharpened chain. It cuts like a knife through butter and so quickly, causing less fatigue. I never got the chance to try a 24"/25" bar sadly but it always cut well with a 20" bar. I went through several bars, the best being the genuine Stihl bar it came with, but I didn't want to spend $160 on an over-priced bar, so the second best bar it ran was a hard-nose American steel bar off ebay. I've found hard-nosed bars are much better, as they last longer/ don't wear as quickly as sprocket nose bars. I was told the maximum size bar to run would be a 32" on this saw but not for long periods!
Apart from oil pump, worm gear, clutch drum, sprockets, chains and bars, I've only ever had the ignition module pack it in on this saw which was about $35 to replace after-market.

1. Try to always cut each tank load with a freshly sharpened chain to really unlock the power of this saw. And keep rakers (depth gauges) at right level.
2. Clean air filter regularly
3. Make sure you're running between 25:1 and 50:1 fuel mix (perhaps vary it from time to time) with quality 2 stroke oil (I use Gulf Western because it's the cheapest but even with Husqvarna et al. I mix at slightly richer than 40:1. The only problem with GW is it's green and looks the same colour as straight petrol just to confuse you).
4. Wire brush spark plug regularly
5. Avoid adjusting carby fuel jets unless you absolutely have to (ie. it won't idle or seems gutless on full throttle).
6. If it struggles to run properly and there is spark, ever so carefully take apart the carburettor and clean all the parts of it in petrol, making sure not to damage the diaphragm or put it back on upside down. If the diaphragm is crinkled when held in by the tiny screws, you'll need a carby kit installed.
7. Only get it serviced by someone who doesn't sell chainsaws new or at least don't take what they say about its future at face value.
Happy chainsawing :)

Date PurchasedJun 2014

Excellent saw, always starts, cuts through everything. Worth the money.

Have owned my Stihl MS 391 Farm Boss now for about 5 years, and it still runs as good as the day i brought it. I would suggest that my saw gets more use than the average residential user, as our only heating here in a cold area is our wood heater. I do get the saw serviced regularly at the Stihl dealership, and I look after it very well between services. This saw has never let me down, from felling 40 + metre high gums, to prepping firewood, this is definetly my go to saw in my shed. I do also have a smaller Stihl saw that i use for the lighter jobs, and it always pays to have a second saw, so you can cut the first one out if you get it jammed! This saw has been brilliant for the last 5 years, and i can not see any sign of it not lasting another 5 years and hopefully more.

Date PurchasedDec 2011

Stihl ms391 review and starting tips, January 2015

I just got the ms391. It is a great saw. It starts quite easily if you do it properly ,and it really does go through the wood in a hurry. I cut down and processed a fair sized , dead, seasoned elm , which is pretty hard wood. It was a pleasure to see how fast the big trunk was reduced to fireplace length pieces. Stihl highly recommends using the green chains, but my 391 came with the yellow chain. It worked fine for me and cut very fast.

Regarding hard starting on Stihl chainsaws- you can probably read this same info in other places, but anyway I hope this helps…
1. use gasoline is fresh and has the proper oil mix.

2. don't pull the start rope too many times with full choke. Once flooded it is a problem. Just pull the starter with full choke until you hear the little "pop" sound, then switch to the fast idle setting for the next pull.

3. When finished working, make sure to run the saw until "dry" ( all the fuel in the carb and line is used up). Do NOT store the saw for a long time with fuel mix in the carb and lines. That just about makes it impossible to start if you wait a long time before trying.

4. My Stihl dealer says that ethanol gasoline(10%) is fine as long as it is fresh and you don't store the saw without running it dry first. I have found this to be be valid information.

Numbers 1,2,and 3 above are all of equal importance.

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Questions & Answers

Purchased 391 July 2018 used it for about an hour in august, no probs,heaps better than my old 039 that it replaced after 20 trouble free years. Last sat, Feb23,used the 391 and my ancient 024 to cut up a gum tree that came down at xmas,024 as usual no probs, 391 difficult to start,kept flooding,in the end full throttle and kept pulling till it started. It ran well for about 40 mins then DIED,hole in piston!!Used the same fuel,mix,stihl oil and 95 ulp, in both saws and same cutting technique. Can only guess that carby set too lean at factory,faulty crank seal,or just a crap chainsaw??? Any ideas??
No answers

Will a piston and cylinder from a Stihl MS390 work on a Stihl MS391 ?
No answers

Why don’t they make the MS 390 anymore? Did this model have a safety issue? Did it have machanical issues that caused it to be discontinued? We recently purchased one second hand and I am having trouble finding parts for it. It runs great now but if parts have to be ordered are the parts for the ms 391 compatible to the ms 390? It also came with the Rollomatic Es guide bar that is 25 in. I have learned after my research this is not the origina guide bar for this machine. Will this cause any safety issues? My husband is experienced with chainsaws. I am only wondering because he will be using this more often to cut down and slab cedar and cypress trees and the occasional problem branch/tree for family and friends.
No answers


391 FarmBossMS 390
Price (RRP)14991199
Release dateMar 2008

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