Stihl MS391 Service, Modification, and Tune

[@TractorsNStuff]

There is a noticeable blank spot, just as I show what it sounds like with the volume unedited. However, I think I messed up the editing and actually cut that clip instead of copying it, and of course, didnt notice until after I published the video. That clip is at the end. :)

[@REDLINERUNNER]

I bought myself a brand new MS311 last year which is exactly the same saw except few cc smaller cylinder. Extremely happy with it. Running it 100% stock and it came without spark arrestor screen. Runs amazingly...

[@REDLINERUNNER]

One small advice on cleaning the bar is, take a thin knife and run it through the groove of your guide bar to clean it..

[@REDLINERUNNER]

One more thing to teach you. That flap for warm air shouldn't be removed. That flap should be lipped with sunny symbol up unless if you run the saw below zero, then it should be flipped up with snow flake symbol up. It will allow some warm air to reach intake and prevent the air filter from freezing...

[@REDLINERUNNER]

And I guess that spark arrestor screen is only in North America, because here in Croatia (Europe) the only thing inside exhaust is baffle and hole to expell exhaust gases. As baffle I mean just a perforated pipe that silences the sound of explosions and creates some back pressure. Two stroke engines need some back pressure which increase the compression, because two strokes don't have valves... I think for European market the exhaust is just right because it doesn't have mesh to slow the exhaust gases... My MS311 is 59cc and hole on exhaust is 12mm or 14mm not sure I didn't measure, but runs incredible and it burns less fuel so gives me better fuel economy. Probably gives me more longevity. I just LOOOOVE my saw... I have two. My old one is MS230 from 2005 and bought myself MS311 last year.

[@byt3b4dger]

Short Info for you: The LA hole stands for LeerlaufAnschlag (German for idle stop ;))

[@templarslayer1317]

I don't know if it was said by someone else, but the small plastic piece for summer/winter mode is designed to be flipped over and put back in the saw. You will notice one side has a sun (summer) and the other a snowflake (winter). Great video overall, just got a 391 myself!

[@liamtopham3551]

What is this?

[@Chad-v4j]

My 391 is a beast

[@travishicks5521]

Very helpful video on the fuel filter. I have the same saw and love it, I haven’t had it bogg yet and I’ve cut some super big trees. I’m giving it a tune up for the first time, found the same tune up kit, and was wondering how to change the fuel filter, now I know. Super simple

[@HabeasJ]

I've come back with a warning about the muffler mod: double and triple check that the exhaust is not hitting the plastic housing anywhere. After about 4 tanks (2.5 ish hours) of work I noticed a spot on the oil tank that was beginning to melt and burn. Just a word to the wise that if you do this mod, consider only doing the top two cuts and/ or verify you've angled the slits away from the saw body

[@thedude8976]

I can absolutely see what you are saying. Thanks bro for your input 👌

[@IndianaDoug]

@TractorsNStuff I wouldn’t listen to but a couple folks in this comment section. I’ve been around and have worked on saws my entire life. This video was great with the knowledge you have. Hats off. Now, the only REAL critique you need is on the limiter caps section. The white plastics inside are limiter caps. With the carb off, take needle nose pliers and pull them off, if they break it’s fine. However, you shouldn’t have to do this. If the carb is healthy, it should tune well with the caps on. 1 to 1.5 turns out to start tuning. If you want to get a little better throttle response tune the Low jet, more rpm in the cut, tune the High jet. Also, a good rule of thumb is to have the muffler port (the hole) 70% the size the exhaust port. This might also be the only reason you need to retune your High jet beyond the limiter. Best of luck, you did a fine job, great explanation of everything👍🏻

[@TractorsNStuff]

Thank you for the awesome kind words! Those limiter caps look to be a pain! Fortunately, it tuned just fine. Thank you for watching and commenting!

[@HabeasJ]

Oh, and the best way to untangle a chain is to lay it flat on a table or he ground. It doesn't sound like it matters, but it allows me to untangle it quicker

[@inaamod]

Didn't see any answers to the question stated, so here's mine: I have a lot of similar cans, which came from the National Archives of Finland. Apparently those were used for storing rolls of film negatives.

[@TractorsNStuff]

Bingo!

[@HabeasJ]

I agree that the dogs are way too small. I changed them out on my 391 immediately as well as added a 28" bar and full house, handfiled oregon vanguard chain. Its a beast that bucks 3' logs no problem, but I know I can get a bit more speed from the muffler mod . Thanks for making such an in depth video. You gained a new subscriber

[@Patriot-Logic]

17.39 you did not read the manual if that’s a 391! You making the situation worse! You flip the plastic deflector around so the snowflake is up for winter! Double check your manual! Great vid👍

[@offplanetevent]

Next time move the piston up to top dead center or close to it. Added precaution to keep debris. And you can use compressed air to blow it out when you're cleaning up the cooling fins.

[@flapjackson6077]

Dude, very good procedure for dialing in the fuel screws! And as you know, a tach is a must! I’ve got a 390 I modded several years ago. I set the max rpms to 13,500 and have had no problems. 32:1 mix.

[@TractorsNStuff]

Thank you! I appreciate the feedback. Thank you for watching and commenting!

[@gunterbecker8528]

400c is the way to go

[@ryanray6344]

The owners manual says to flip it to the snowflake side for winter

[@tractortalkwithgary1271]

Excellent job. You went to a lot of work for this. I have the MS 390 for my big saw and have it for quite a few years. It has served me well and after watching this video, I will make it even better. Like you said, there just isn't much out here for the 390/391 saws. New subscriber. You sure earned this one. I just did a video on my channel of an interview with my local Stihl dealer on the MS 500i saw. Man is that thing ever a beast. Just a bit beyond my budget though. Thanks for sharing. Great job!

[@TractorsNStuff]

Awesome! Thank you so much for the kind words and for subscribing! More content to come!

[@UFRooster]

I was just thinking the muffler “caps” might be there to retain the screws in case they vibrate loose?

[@sylvainleroch1719]

Hi, @27:27, it seems that you have a nut near the piston, inside the exhaust tube.

[@vic2796]

Shit your right

[@davidstout6264]

Next time you should use something like a nail file and clean sawdust out of the chain track of the bar. It will keep oil flowing better to chain

[@bullofthewoods9374]

easy way to untangle chain is to lay it on the table flat and move it around till its right

[@liamtopham3551]

I have a couple questions, I am just getting into these engines and want to learn things the right way. I am looking for upgrades that improve the functionality of the saw without compromising reliability. I am watching this with subtitles in a starbucks rn so I may have missed you talking about it but how do you feel about plugging the decompression valve? Also, when porting, how do you calculate your timing numbers? Porting is something that I am hesitant to start until I can understand how to quantify the amounts I want to remove.

[@Cycletherapy420]

I found one flaw. Small exhaust bolt broke under normal operation. Have to drill and extract about 3/32" bolt. Fun fun.

[@TractorsNStuff]

WOW! I'm guessing that much bolt must have broken off deep down inside? 3/32" is not really that much, but deep down in there is probably a nightmare!

[@jeromynolan1381]

I have a MS291 that I just bought. Might look into the muffler mod also.

[@fullhousebuckin]

Where did you get the full wrap handlebar?

[@Pit315689]

Overall, helpful to those new to chainsaws, but please get your script improved and your ‘order of march’ i.e. have the bits and pieces you’re demonstrating ready to go e.g. the fuel filter still in the packet.. also get rid of those long pliers, just use a length of wire with end bent to form a hook 🪝. Cheers

[@markcarey5673]

How does that modification affect the warranty of the saw?

[@jaahljuu5713]

a huge haawa from Haida Gwaii bud

[@dysonbeasley14]

I have this saw as well, do you honestly think it runs and performs better now ?

[@TractorsNStuff]

I do. Though it may also be the chain, but It doesnt seem to lug down as much while in the cut. Thank you for watching and commenting!

[@modifiedmechanix]

Good video

[@jamessondreex9150]

Thx from france bro !

[@fasx56]

Tractor Nstuff I have a 391 and when I start it I pull the cord 3 or 4 times on choke and then move the lever up a notch and pull to start. It usually starts and until recently it would go into fast idle but the last few times I ran the saw it would not go into Fast Idle with a cold engine. It wants to idle slower then it should until I feather the throttle and then it finally kicks into the Cold fast idle, is this a carburetor problem.

[@-hbwink-6340]

Thank Nick.

[@joeranger4970]

Get the stihl 2 in 1 file for sharpening works better than the electric

[@TractorsNStuff]

I'll look into it! Thanks for watching and commenting!

[@DaveyBlue32]

Just lift up the handle and push the tip down...you are a smig tight but with that new chain stretching I’m assuming that your compensating for that.

[@stevenmiddagh6265]

If ur 391 dosent cut as fast as a 362 there is some wrong with it. Mine hangs right with my friends 362.

[@TractorsNStuff]

I've never pit this saw against another in a true side-by-side. I simply ran my neighbors saw (that had this mod) and was impressed at how it didnt lug down. So, I decided to mod mine. Thanks for watching and commenting!

[@robertm9848]

Not sure if anyone else caught it but your bar was already upside down before you to it off. So you didnt actually rotate it on this service lol.

[@TractorsNStuff]

Yep! I certainly did! Thanks for watching and commenting!

[@steveyork8069]

I bought a big box of those cans at a yard sale the lady said they were film cans but I don’t know for sure.I have the ms 391 but my air filter is different and my muffler is already slotted in the front and it has the split case like the commercial saws just wondering how old your saw is.Im guessing I bought mine in 2014.👍

[@TractorsNStuff]

Thats exactly when I got my saw, 2014. And your correct about the cans. They are old film cans! Great for holding small parts and whatnot. Thank you for watching and commenting!

[@steveyork8069]

TractorsNStuff Wow,now I’m curious as too why the differences.My air filter is square, bigger cleats and like I mentioned it has the split case like the commercial saws and my muffler is already levered in the front with a screen that I have to pull out and clean ,pretty sure it’s a spark arrestor.My sales receipt is too faded to read the date but my stihl dealer has it on record and they are making me up several skip chains to replace my old worn out ones.If you haven’t tried the skip chains I would suggest it,I use both half skip and full skip chains will never go back too regular chains.Thanks for answering

[@TractorsNStuff]

@@steveyork8069 Yeah, I don't know why there is a difference. Honestly, I don't know much about these saws to know the differences between models, let alone the same model with significant differences! I have used a skip chain, and they are great when I need to sharpen them on the saw for sure! But I have more luck finding the full tooth chains in the hardware store. I have to order the skip toothed ones.

[@steveyork8069]

TractorsNStuff I’ve already been doing some research there are 8 different model numbers on ms391.Im lucky enough to have a stihl dealer in town so I just have them make mine,about $12 more than the Oregon chains but I get much better life out of them.👍

[@boebradley867]

What's the gap on the MS 391?

[@tomztee3756]

Do you think i can upgrade my ms291 with an ms 391 engine??

[@TractorsNStuff]

Thats a good question. I'm sorry, but I do not know. If it bolts up to the frame, and the covers and everything else lines up, I dont see why it wouldnt work. But I honestly do not know.

[@Cutecumber12564]

No, you can't, completely different engine and different mounts

[@georgedavall9449]

Wow! Late comment here, but I just had to say, if someone gave me a MS391, especially a Family member, I wouldn’t be putting it down?! He could have just given you a Farm Boss, or the MS 291? Not everybody needs a ‘Pro Saw?’ And from what i saw, starting @ 04:11, you might want to hone your skills, and develop proper and safe practices, with this saw first?! You even said it was warm, so why you chose to choke it is a mystery? And I get it that Not everyone wants to start a saw on the ground, but ‘Drop starting’ it like you did, was a no no. If, If you're gonna have to drop start a saw, turn it the other way, and your undamaged leg/artery will thank you! The saw will have a tendency to swing down towards the body, the way you were trying to start it, and should yourself, or someone that watched this video, forgets to engage the brake, and the saw fires up, while swinging into a leg, or whatever, well, you get my point! 😳 Stihl advises starting it with the saw held between the legs, with bar and chain pointing away from the operator, if not using the ground method. Please take my comments as they’re meant, and that is for safe and wise use of these machines. I’m no friggin expert, and I’ve done some dumbass things in my day, but I just want people out there that may watch your video, and others, to not copy unsafe methods. I gave you a thumbs up, and I wish you well and please stay safe and healthy! Peace! 👍

[@melchioraelmans]

Great video, thanks!! Can you tell me which meter are you using to measure RPM? I'm looking to get me one as well but only seem to find with laser.

[@TractorsNStuff]

Yep. Here is a link to the one I have www.amazon.com/gp/product/B000FOOAXY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

[@melchioraelmans]

Thanks for sharing!

[@brianmitchell4809]

@@TractorsNStuff do you just leave the wire around the spark plug wires at all times? I didn't see you wrapping it around on video.

[@TractorsNStuff]

@@brianmitchell4809 No need for the wire. The meter is sensitive enough to sense the pulse though the plastic.

[@brianmitchell4809]

@@TractorsNStuff thanks man

[@garyczerkies6924]

great video, i have the same saw and it has been a stubborn pain in the ass since day 1. Hard starting unreliable compared to my ms362. Now no spark, changed ignition coil (gap .020),with new OEM part for the serial number (round air cleaner versus rectangular) new spark plug gap 020. And still will not start. Only thing I have nor done is new gas, but the 362 uses same juice and runs great. Makes you want to toss the SOB in the garbage.Guess maybe time to take it to the dealer.

[@glennr6125]

Did you mean to not tighten the chain.

[@boebradley867]

I have about 5 hours on my Ms 391 and it's the hardest thing to start compared to any saw I have you have any ideas or video you can put on there just with suggestions of starting that bad boy?

[@bullofthewoods9374]

mine cranks fine if i do this, choke , start lever pressed on throttle and pull till sputter ( three times) then flip choke lever up on notch and pull should fire right up. had mine 14 years and its a beast. if this does not work i would think you have a spark plug issue ( doubt it) or a carb issue. if the plug is sparking and not cranking you got a fuel issue either in tank ( filter ) or carb.

[@i1bike]

@@bullofthewoods9374 that is why makita has new 40v chainsaw, NO COMPLICATIONS for home owners. Tho, ms391 is for homeowners that need cheap saw thats stronger than ms291

[@bullofthewoods9374]

@@i1bike battery has come a long way for sure but it wont do the job for me. i cut 8 to 10 cords a year. battery just wont do. i actually had a makita back in 95 and it was great, i ended up getting a farm boss then the 391. and the 391 is not a cheap saw its about 600. its the largest non pro series in that line, also my brother just got the 400 in pro series and i have to say it a nice saw but it doesnt do much more my 391 cant. it is a bad ass saw though. but at 900 it should be.

[@i1bike]

@@bullofthewoods9374 Here in croatia, which is 500km from germany, ms391 costs 950$ and ms400 costs 1350$. Normal croatians work for 600-700$ a month, so that ms391 for 600$ is a steal. Here, with 600$ you can only buy ms231 haha. Compared to stihl, husqvarna is little more expensive and makita is little more cheaper, while echo has bliblically high prices. Echo cs-4310es thats 43ccm saw costs 850$. So, you shouldnt take for granted some US benefites.

[@bullofthewoods9374]

@@i1bike Im not taking anything for granted. I am surprised at the cost difference there to here? i wonder why that is, maybe a tax thing or tariff thing not sure? All of those saws are great saws. im just a stihl guy. i heard echo is coming in strong but they are cheaper here also than stihl. its funny many in canada use the huskys. to each their own i guess. all great tools

[@rwilko9525]

The mrs is getting us a 391 for camping. Is it a good saw?

[@TractorsNStuff]

It is a very good saw! I cannot think of a dislike.

[@billyw.1741]

Only dislike is the transfer port covers are pressed on, and they sometimes come loose. They say there is "no fix" but I've put JB Weld on and it's doing fine so far. If they come off again, I'm going to weld them on! It's a horrible design. Some people gave even drilled into then and added bolts to keep them tight!

[@mikeoxhard2176]

At what point is the muffler modded? I can't watch a whole hour lol

[@mikeoxhard2176]

Found it, but leaving my comment for the algorithm

[@TractorsNStuff]

Its at 21:30. Its a long video, I know. I try not to make horribly long videos, but I never know when to cut it off and make a part 2. Thanks for watching and commenting!

[@ryanshanebrook209]

Do get those plastic screw gaurs out of the carb without taking it out, just use a screw and pull them out.

[@stevenkleinhenz1017]

My MS 391 has been a problem child but it’s easy to work on and parts are available so I don’t want to bitch! I’m almost done cutting trees so when I’m done someone else can work it!

[@MrScottgp]

The green label on the chain package means it's a low kickback home depot chain. Do yourself a favor and put a real chain on it first not a safety chain, then worry about mods.

[@minnesotatomcat]

I think that’s an old pomade can isn’t it?

[@TractorsNStuff]

Close! It's an old film can. Thanks for watching and guessing!

[@logicVSpassion]

stand up and buck!

[@aaronmcclelland2899]

You put the bar on upside down 😂

[@RickBonjour]

If you listened he did it so the bar wears evenly as it wears out faster on the bottom side.

[@clarencejohnson7232]

100' load of 35mm bulk film!

[@jacobhasson7154]

For the chain tangle situation. Lol you can't really explain how to make it easier. It's just one of those things. You'd have to be there kind of thing.

[@TractorsNStuff]

Hey sorry, I just saw this comment. I struggle with the chains every time. Thank you for watching and commenting!

[@kirklucas1332]

We dont need to know how not to start a chainsaw as shown. We're here to see if you can fix stihl junk and how you did it. Currently own the last new stihl chainsaw i will ever own. Cant keep it running. Dealer cant fix it. Says its fine. 2 other places declare its fixed. Its not. Its worse than useless. It starts when cold. Floods easily and you wear yourself out cranking on it after the first run. Only way to start it after its warm is to jam the throttle wide open as you would any flooded engine which makes the saw a safety hazzard. Ive come to the conclusion that i will have to order all the tools to test every part of the saw and fix it myself. Stihl saw dealers are to incompetent to fix it or make it good. Failing that it will turn into a Husqvarna.

[@scratchnuts]

You should learn to start that stihl without drop starting it..unless you like changing the clutch out...

[@georgedavall9449]

Or taking out a femoral artery and bleeding out on top of your saw! Great comment! Thanks!

[@CantgetRit]

snuff can