Stihl MS251 Chainsaw Carburetor Removal and Cleaning

Stihl MS251 Chainsaw Carburetor Removal and Cleaning

[@skylerjohnson1827]

I got the same exact saw a few years ago and I'm about to tear it apart now. Thanks for the video.

[@silversurfer100]

Just completed a complete fuel system cleaning and fuel line replacement on a 251. I can honestly say I have never seen what could and should be an extremely simple design become exceedingly complex and difficult to perform. It quickly became obvious Stihl design engineers and product managers completely despise repair technicians. For those that encounter a "sticky" soft start recoil pull, a tip. Remove the recoil starter cover and clean off all the dirt, oil, and debris from the starter rope assembly. No need to take the rope spool out of the cover or remove the rope, jusy spray it down with Simple Green or Purple Power and brush all the crap away, then rinse with a good stream of water from a garden hose. All that dirt and crud builds up over time on the pull starter and causes it to bind.

[@floydrturbo1]

So you're not going to actually show the cleaning process, which holes, what product you used, how did you go about removing cleaning solution, etc. That's the whole point of this video beside disassembly and assembly. Need more direct to the point and skip the superfluous chatter.

[@ops-uk]

The first few minutes were some waffle about whether it was 8mm or 'normal' (8mm IS normal in most of the world) . I kept having to fast forward to get past the repeating if the same thing over and over again. If it could be significantly shortened and more on point, this would be excellent rather than good. As I say to many people, write a script and work out what you are going to say prior to recording. This stays on topic and gets the message through much more clearly.😊

[@jjclarkson3261]

Your video angles and showing all the parts and where they go, tips to remove and reinstall were all excellent!

[@A_Renaissance_Man]

Thank you

[@cubfoot4198]

Awesome! Thank you so much. I went the way of the slightly turned down sacrificial 8mm nut. Your vid saved me a lot of time.

[@markschnitzler4897]

The only video that even has a clue on putting the throttle linkage back on an MS251. Thank you!!! At $80 an hour i can't imagine ever letting a dealer work on my Stihls. Found a 9:56 on your video.

[@A_Renaissance_Man]

Excellent. Thank you for pointing that out.

[@mikeparker2865]

At $80+ an hour I’ll never have to worry about a shop ever touching any of my equipment.. I’ve been working on cars,trucks, farm tractors, etc since I was a teenager.. If I figured out how to do that I can figure out how to do the same on small engines…

[@CoryCard85]

Thank you so much! This helped me fix my saw today and I was able to clear out a fallen tree due to some late season snow.

[@tzionsimchy5496]

Your video had convinced me to subscribe and say thanks for your help with the Stihl chainsaw. I do have the MS291 and it's kind of similar carburetor to the one you showed. The first issue as you mentioned was the damn 8 mm socket thin wall to fit in the holes and get to the nuts. After visiting few stores with the chainsaw with no luck, I just took out an old short 8 mm socket and polish it gently on the grinder wheel; it went in nicely. The rest of it with watching your video was easier, thanks to the great video quality..... I did not have the good spirit as you had since I wanted to get it done as soon as possible....It was tricky to return the needle valve assembly and finding T-5 key or some torx that fit. I found that screen you mentioned plug with dirt from the gas.. When I replaced the fuel filter in the tank I notice that the old one was cracked...... Bottom line, the machine fire up after many crossed fingers.....Thank you again...

[@paullovejoy6018]

did you try 1/4 in drive socket ? a 5/16 is exactly 8mm

[@deigo2629]

There's a lot of great content here ... you just got to wait and wait and wait for it

[@jjclarkson3261]

1.75 speed is about perfect

[@steveturner2460]

Had teh same problem with carburetor nuts: I figured out they are easily removed using a multiple tool screw driver. The one you can take the bits out of and flip. The 5/16 hex end works perfectly.

[@A_Renaissance_Man]

Thank you. That is great advise.

[@mikeparker2865]

I just said screw it and took the bench grinder to a 1/4 inch drive 8mm socket I didn’t really care about 😂😂😂

[@DescartesDooley]

I tried this, but the bolts were too long and not enough depth in the screw driver recess to reach. I spent the 20 bucks on the stihl tool. Easier than buying a cheap wrench and grinding down. I also don't have a grinder anymore

[@MrBalddawg]

You disassembled the metering assembly but didn’t check the metering lever height when you reassembled.

[@A_Renaissance_Man]

You are correct.

[@juniorboyd6974]

I tighten / adjust my chain after each top off oil and gas. At least check it by pulling. Only time I’ve had issue with one nut was not checking it.

[@andywylie287]

Thanks for the vid. Some useful info here. Now its time to get that carb of mine off!

[@mario7mag]

The Project Farm channel has an amazing review on electric chainsaws.

[@elbotsnoc]

I have a 291, same carb, and it's a special tool, thin walled 8mm T handle socket. don't know why they did that! but I ordered it for about $8. fits perf.

[@A_Renaissance_Man]

Thank you for pointing that out.

[@keithrayeski6417]

Just ordered mine!

[@danielz4111]

Thanks so much! I too was able to fix my saw that took a dive off the back of my truck. I didn’t know how the throttle was supposed to look.

[@A_Renaissance_Man]

Your welcome. I am very glad this helped.

[@erwinrommel2055]

O yea the dreaded 8 mm. But all in all you did a great job I learned a lot. Thanks for your time and experience.

[@charlesmartinez5171]

Thanks for clarifying that a smaller 8mm socket will fit. I'm still struggling to take mine out.

[@A_Renaissance_Man]

Believe or not they actually make a 'special tool' for that. Fun Stuff. Good luck, it is not too bad when all is said and done.

[@charlesmartinez5171]

@@A_Renaissance_ManBelieve it or NOT! I'm still trying LOL

[@slingshot909]

Your video was the best I've seen, you explained how the metering device went in and the two holes for the adjusting screws, I almost put that in wrong. Great video!

[@A_Renaissance_Man]

Thank you very much for taking the time to leave your nice comment

[@MrBalddawg]

The diaphragm doesn’t pump the fuel. It meters the fuel. The opposite side of the carb is the pump, consisting of the pump membrane and two one-way valves.

[@annaaron3510]

Ignore the dumb critics about talking; it's how we all work. Good job. 8mm did it for my 261...thx.

[@PeterBaumgart1a]

My 251C's carburetor, at least externally, looks just the same! (You mention somewhere that it's "completely different.")

[@wishbone54]

Thanks for the detail.

[@anderslindstrom8195]

Following up on my comment about the special Stihl tool “STIHL 59108902420 8mm T-Handle Screwdriver”. I didn’t buy one in the end. It’s about Australian $30. Instead I bought a 8mm socket for $6 and then carefully ground it down with a zirconia flap disk on my angle grinder. Works perfectly.

[@user-ht9fg2xr4q]

When you started your saw the idle was so high the chain never stopped, so how could you say you fixed it? If it was idling normally, I would believe it.

[@A_Renaissance_Man]

Two different things are going on. I fixed the carburetor and the fast idle is caused by the choke being on. The choke is turned off by the first pull and release of the trigger. Then the motor goes to idle. Sometimes I don't express my thoughts clearly. Thank you for pointing that out so I can correct that.

[@3BTruck]

Hi thx for that video! I just finished the same procedure...but cant succeed in getting fuel pumped. For some reason fuel is pressurized until the inlet of the carb but wont go further so that there is no fuel in the primer bulb. Cant figure out why, if someone have some idea to help :-)

[@A_Renaissance_Man]

This was three years ago for me but, I do remember that the reassembly was very easy to get wrong. Each of the four gaskets had to be oriented correctly and the reassembly was orientated backwards from disassembly. In other words, I would suspect that one of the gaskets is orientated incorrectly and that is preventing the fuel from going to here it needs to go. Each gasket can be put in wrong by being up side down or 180 degrees out (Backwards). Good Luck and I hope this helped.

[@3BTruck]

@@A_Renaissance_Man In fact, I just simply started the engine which ruuns quite fine but still fuel in the bulb, I will eventually guest whats happening later.

[@JimDon-xj5qp]

Thanks for the video. My MS251 has become bane...as it is near impossible to start, and I've been looking for a good tear down video. Also, good to know about that second nut! I'll make sure to use a really thin walled socket to tackle this. I assume you're using a 3/8" ratchet; perhaps you'd have better luck with a 1/4" drive ratchet, or a nut driver...just a thought. Finally, I hear you about 'going electric'. However, until e-chainsaws get to where they can match the hp of the gas engine, I'm sticking with gas.

[@A_Renaissance_Man]

Excellent. Electrical saws just are not powerful enough for trees. Smaller branches can be handled but trunks require the more powerful gas engines.

[@JimDon-xj5qp]

@@A_Renaissance_Man Well, I've just torn down the carb on the MS251. And, for everyone else who may struggle with the 8mm nuts on the air cleaner, forget the socket; it turns out the 8mm nut driver is the perfect tool. It fit easily into the very tight cavity, and I was able to get on the nut with no problem. I tried several 8mm sockets, but not one would fit into the small space to get at the nut. Who designs these things, anyway....geesh.

[@stihlhead3338]

If you switch to 1/4" drive socket you can then use metric or standard.

[@A_Renaissance_Man]

Excellent idea. Thank you

[@herrent]

Did you show the air and fuel path

[@A_Renaissance_Man]

No I did not since the mixing point at the venturi was really the only obvious point of interest, I decided not to guess and be wrong about the liquid and air paths.

[@cbk-te7ru]

Constructive criticism Use 1/4" drive with 8mm deep socket to fit in narrow access holes

[@A_Renaissance_Man]

Excellent. Thank you. I appreciate your input. Sometimes, I need all the help I can get.

[@cbk-te7ru]

@@A_Renaissance_Man no...... thank you.... Out of the half dozen videos that came up ..... yours was the most detailed that showed exactly what you were doing in your tear down. Helped me with my project immensely......👍👍

[@ButterflyMatt]

For the record, I have more than one 1/4” drive deep well 8mm sockets and none would go in the plastic access holes without having material removed from the outside. So I sacrificed/dedicated one too.

[@dereksteele2284]

It has to be thin wall

[@PeterBaumgart1a]

Did it really start on first pull? Or did you cut out a few attempts? 😅

[@A_Renaissance_Man]

1st attempt even to this day. No kidding, tricky editing, or cheating.

[@adambell3136]

Would this work for the 261c?

[@A_Renaissance_Man]

I would think so as the larger engine is just a bigger piston.

[@adambell3136]

@@A_Renaissance_Man I'm more worried about messing the computer chip up to be honest 😅😂

[@erikwright6539]

I cannot find a 8mm socket that'll fit in that deep hole. Found a crappy old socket and used a diamond flapper disk with the socket on a drill mowed the sidewalls down

[@A_Renaissance_Man]

I have been told that a special tool is used but I was able to use the 8mm by pressing on the socket and finally getting a bite on the nut.

[@dougyoung2177]

Sooo glad you told me the size of those nuts at 8 mill. Very tight fit

[@tomsmith4484]

You had me at, it's for your safety! Then you lost me at going electric.

[@A_Renaissance_Man]

Turns out my electric endeavor is only good for small stuff and I still need the gas powered saw for tree trunks and logs.

[@jsimm4587]

A 8 mm is .0025 bigger than 5/16 the outside socket is a commercial socket I’m sure Stihl has a special tool .

[@A_Renaissance_Man]

You are correct, I have been told that there is, in fact, a special tool involved.

[@azardkhan2932]

What other model diaphragm gasket can work???

[@A_Renaissance_Man]

Since I do not know if other carb gaskets are the same, you can buy a gasket material sheet at the auto parts store and make what you need. The gasket does not have to be perfect or look good. A pair of scissors and a razor knife should be all you need. Good Luck

[@azardkhan2932]

Actually it's a diaphragm gasket

[@PeterBaumgart1a]

I measured the ODs of my two 8mm sockets, the long one is 11.9 mm, the short one is 11.6 mm! The short one fits!

[@user-jm4uv6do6y]

Any problems with stihl 251 ?

[@A_Renaissance_Man]

No problems. Had to clean the carb, but that is a fuel gumming issue and has nothing to do with the saw itself.

[@juniorboyd6974]

When storing it empty out all the fuel and run saw until it dies.

[@davidjero6441]

I would have preferred seeing it started from a cold start. After all. Wasn’t that the original problem?

[@A_Renaissance_Man]

It started right up. Maybe I filmed the second start. I'll have to watch this again. I definately don't cheat in my videos.

[@hepeng2627]

THANKS SHARING THIS VIDEO

[@nicklloyd9165]

I appreciate the work you did for this video. Stihl should really use Allen head bolts instead of those 8mm socket heads.

[@Patriot-pq1ku]

That linkage for the carb isn't as smooth as my 170 the 271 is kinda rough with that flip up design maybe it's just me thou

[@anderslindstrom8195]

I think the correct tool is called “STIHL 59108902420 8mm T-Handle Screwdriver”

[@A_Renaissance_Man]

Thank you, I appreciate that info.

[@nicklloyd9165]

THANK YOU

[@MrChad92100]

I'm here because I'm having the same trouble trying to figure out what size those nuts were as well!😠

[@tjon66]

Those 2 nuts seem to be the hardest part

[@hdalebeggs8786]

You didn't even mention the high and low speed mixture adjusting screws.

[@A_Renaissance_Man]

You are correct. As a matter of fact I have never had to touch them on any Stihl product I have owned.

[@randysmith8604]

Why are you taking the carburetor off was it not running I assume. I have this saw and never have a problem. Run clear gas only!! They have problems staying tuned. You need to know how to adjust the carb correctly or you will make it run worse.

[@jimdever4346]

Great -- so completely skipped Primer Bulb removal/installation unless 251 doesn't have one. 251C does however.

[@A_Renaissance_Man]

Thank you for your comment. There is no primer bulb on this model. I do have a how to start video on this model which demonstrates how this starts without one.

[@jimdever4346]

@@A_Renaissance_Man Good, but I have a 251C

[@chrifaranaudo123]

So find a different video

[@kcpiggott10]

@@jimdever4346 good for you!

[@ButterflyMatt]

I’ve watched 7 and a half minutes of your video and finally learned how to get the plastic part off the carb. Now I’ve heard about two minutes of how you don’t have or weren’t using the right socket to remove it. The title of this video implies that you’re going to show us how to do something, but I have to quit watching because I feel held hostage by your talking and talking and talking. You also showed how to remove the choke linkage without even mentioning what it was or why. So you’re talking a lot, but not saying things that are useful.

[@A_Renaissance_Man]

I am not a technician. This was a learn as I go video.

[@ButterflyMatt]

@@A_Renaissance_Man I get it. I learn tons from regular people like you sharing their knowledge. I’m sorry to be a downer, but your content would be much more palatable if you didn’t go on repeating yourself about the minutiae. Unless you want fewer views and a one in six dislike stat.

[@keld101]

Fixed it.

[@fleamine]

The nuts were hard to get off because you use the wrong tool. try the 5/16 driver screwdriver. take the flathead bit out and slap it on. EASY.

[@ureasmith3049]

1/4 ratchet better for those 8mm nuts.

[@A_Renaissance_Man]

You are correct and I dont know why I used 3/8ths.

[@Kumanekosamurai]

You're extra bud

[@jimmyhuffman6802]

Was looking into buying one of these saws, but seeing your video has told me to go back to the ms250. These pieces of junk are made as cheap as the company could make them and sell them for to much money. They just won't build a quality home owner saw. Even went as far to only use one lug nut on the chain tensioner. And take a look at all the plastic in the carburetor and throttle assembly.

[@A_Renaissance_Man]

I agree with you on that point. They are make for maximum profit not maximum quality.

[@aportilla007]

I'm dealing with the same saw, same bullshit - after cutting down just 3 trees - 1/2 day work. It is built cheap. I would have never bought it if I'd known.

[@user-dh1qh4vf2i]

If you use the craftsman 1/4 inch drive and 8mm socket you could eliminate 10 minutes of dialogue and grumbling. You did not address cleaning of the high and low speed adjustment screws.

[@raenrfm]

You know it's a German saw right...of course it's 8mm.

[@A_Renaissance_Man]

You are correct.

[@PeterBaumgart1a]

What is 25.4 times 5 and divided by 16? (The difference to 8 is within most screwhead's tolerance.)

[@go2sully]

Talk way too much. 35 min should have been 10. Informative, but too much talking about useless stuff.

[@marinamile]

Lets see you do better!!!

[@larrymccormick9954]

Don't be stupid, you'll change back . Evidently you only use one probably every 2 or 3 years. Backyard cleaning. Electric runs about 30 minutes and quite, then recharge time you probably work hard need a 1 hour rest anyway.

[@A_Renaissance_Man]

I had realized that electric is the way to go for me. At the time of this video, electric was unavailable.

[@jonathanholmberg9421]

German design, almost always is going to be metric bolts and screws.

[@herrent]

You skipped half the steps

[@rawlinsclarke7891]

BWXT lol

[@A_Renaissance_Man]

Did I say that? Hopefully I did not devoluge any Confidential information, 😆

[@Skinnymoose]

Electric sucks. The batteries are expensive, they only last so many charges, you need tons of them to work all day, they dont work good in the cold, or the heat, and they are hazardous waste.

[@A_Renaissance_Man]

Well, the truth, the whole truth, and nothing but the truth.

[@rayleblanc9914]

Little less jabber ,you go on about to much detail ,the light the screwdriver everything except where the coffee cup was made for God's sake .

[@efrenrosales8451]

Muchas Grasias por este video porque yo tengo esta motosierra 251 y quiero cambiar el carburator

[@slingshot909]

Why not drill the plastic so that your socket fits in it? I used an 8mm long socket and it fit fine. They must do this on purpose, so you'll get frustrated and take it to a repair shop.