Stihl 021/025/MS210/MS250 a common air leak & engine removal full tear down disassembly

3rd one of this "family" of saws that I've come across with the same exact air leak. They may not all have this issue, but it's enough for me to call it a common problem. I believe it originates from not keeping the head screws properly tightened. They loosen up over time and use.

[@replikvltyoutube3727]

Thank you for this complete disassembly demonstration. I find it very helpful. Trying to repurpose an old chainsaw as an engine for bicycle

[@corkydavis5688]

Thank you for the video. Very well done!

[@ben-me9jy]

Thank you very much sir! I have a 021 so this breakdown is very similar!

[@ex-engineer6657]

Thanks. We were just given a ms250, not running. This looks helpful. I'm hopeful.

[@stephenbrown5844]

Excellent thanks for the footage my friend, very informative 😊👌❤️🇬🇧

[@johnclarke6647]

I am restoring the 021 that I got off EBay. The cylinder was ok, but the rings were slap worn out. I am putting a new Nikasil cylinder set on it with Caber rings and a new crank because the rod bearings were also worn out. It will have new seals, boot, fuel line, filter and impulse line. If I have to go into a saw I rebuild it from top to bottom. In do not ever want to have to go in it, again. It also is getting a new clutch, sprocket, worm gear and sprocket bearing. It will also have a new Stihl L4 lightweight, 18”, .325 bar and chain. If it will not pull it I will put an LP 3/8 chain on it. The crank is a NOS Stihl crank.

[@jamesbailey7785]

Good Vid.. I watched many and heard those plastic plugs holding handle on where a bear to get off. I found an old 311 and needed the Handle. I wiggled my small screw driver into each and shot a drink of white grease let them sit and they all popped of fairly easy.

[@DouglasHopwood]

That was a great video. I would love to see the reassembly

[@boblockerbie7726]

Thank you for this video I'm replacing the engine on my 210. Hopefully my new one doesn't leak.

[@nsn713tgp2]

Where does the Impulse Line even connect to? One end feeds the engine block so where does the other end go?

[@mikw1809]

Good video, thanks for taking the time to make it. I'm about to tackle mine. My 025 symptoms sound similar to yours, will run ok, but loss of power when under load and impossible to get the low/high mixture settings right. When idling, if I push weight down on the handle of the saw, engine will stall. That's how I found your video, thought it had to be an air leak, and having seen your video, it now makes sense. Will try and tighten the main bolts up first to see if it helps. Thanks again

[@J.E.Taylor]

Mik, did you ever solve your problem? I've had a bit of a time with a 025 I got for a decent price. Seller told me it had issues. I rebuilt the engine with new rings, seals, and bearings. Original seals were shot and a bit of leak at the engine pan seal. It runs ok for a while until warm then would start surging at idle, rpm increase and decrease. Usually would die if I picked it up off the ground. But if throttling, it is OK. If I press on the orange cover over the engine it changes rpm. I replaced the intake boot since it was pretty worn at the carb connection and wasn't sealing very well. Seemed like it was good so I ran it today and back to the surging. While improved in some aspects, it's still not right so I pressurized the case again. The aftermarket boot is leaking at the engine where the plastic baffle presses over it. So, that's my issue now. I'm not sure if the baffle is just not tight due to heat and age, bad tolerance in the aftermarket intake, or a combination of both. However, being that the problem is the same, I'm suspecting the baffle is the problem. Just wonder if this could be something for you to look at as well if you hadn't figured out your problem.

[@shadetreeprofessor5723]

Thanks! Good to see!

[@salva7668]

Sei un grande. Grazie del video.💪👍

[@rogerd943]

Larger TS saws have this same problem with the cylinder bolts backing out. I now assemble with blue loctite.

[@johnclarke6647]

Good tear down video.

[@chrisAldred-qt1qm]

very detailed.. thank you, sir... ChrisTenn

[@williamlaw6109]

How did you know to check that area for leaking?

[@johnclarke6647]

I picked up a 021 but haven’t got it running, yet. Don’t see any air leaks around the crankcase, yet, but still checking. It will pop but not run even with a new carb. I think the carb is not being pulsed, so it may be a broken or disconnected impulse line. I went through the old carb and did not see anything that should keep it from running but I replaced it anyway. Fuel line is also OK and cleaned out the filter. It has good compression but could have a stuck ring. If I have to replace the cylinder it will get a new Nikasil 40mm jug. I guess that would make it an 021 Super. It would then fit right in with my 024, 025 and 026. I will then put an 18” L4 bar and .325 chain on it. It ought to honk with a 40mm jug on it and pull an RS chain pretty good. I will replace just about all the rubber parts on it, as I do on all my restorations.

[@johnclarke6647]

Use Three Bond 1284 on the case seal. It won’t leak or get destroyed by gas. I se 1184 for all case seal jobs. I have never had one leak, afterwards. The first seal job that I ever did was on an 029 Stihl. I used a Ermatex sealant and it did not last a week. I resealed it with 1184 and it is still running, fine.

[@wierpkevin]

1184 or 1284 ? Is that the same thing or a typo ? I don’t understand

[@johnclarke6647]

@@wierpkevin I useTB 1184.

[@rocks4brains]

How did the problem manifest itself performance wise? How did you discover it?

[@travisthompson779]

is there a cooling plate on the muffler? None on mine and no gasket on mine. Thanks so much

[@GICK117]

Awesome. I now fear not to rebuild my ms250 when all is said and done.

[@russellbreyley6387]

Thanks for the video it helped me a lot you're my new best friend

[@samishsawworks5870]

Haha glad it helped. I had a reassembly video made at the time, but lost the footage before I got it posted.

[@timnels8638]

Excellent how-to, doing my 1st 025 breakdown this has helped many times thru my rebuild. Looks like I had a leak in the same area of the head as your video shows the head was coming apart from the crank body before I was able to get the motor out of the case. The glue that was used was barley there and was clear. The whole head and crank body with case connection design is crap. Thanks for your video.

[@lealamb]

Have you done any port or timing work on any of these 021 saws? I have an 021 that im thinking about pulling apart and would love to do some tuning also.

[@davidschliebe246]

Hondabond is great!!!

[@chrisradla]

nice show and tell! would you briefly comment what are the differences between 021/025/MS210/MS250 please?

[@clearlakebunch8569]

Great Video I have dis-assembled my Stihl MS271. New piston ,rings , crank shaft bearings and seals required, however the old seals have deifferent part no's and one is blue the other is brown and the service manual refers to them as hard and soft seals can you or anyone explain this and which side of the crank they go on thanks

[@nm6405]

A little late, but for anyone else reading... the brown ones are suppose to be able to be installed without taking the engine apart and the blue ones require disassembly of the engine. The pressed in ones (brown) are difficult to get right and it's usually best to use blue ones although alot more work is required.

[@timidater4803]

how could you tell it was leaking? the way it ran?

[@billhacks]

This is a longshot, but I was wondering if anyone knows what the little piece of black plastic that goes between the spark plug area and carburetor area is? I bought a used ms250 and its missing. The manual refers to it as a shutter for winter/summer mode. I've been trying to look it up to buy but have not had luck. I'm sure that if I use the correct name that it shouldn't be hard to find.

[@AndyAlaska375]

They're on eBay.

[@jackfrost8854]

Have a 023 i purchased in 2005.Five years ago i replaced it with a 025 because it would just shut off after cutting a few sticks(Start easy,could never restart it until it cooled off completely). Wondering if this is the problem due to a poor seal on the crankcase(Saw was never apart).

[@samishsawworks5870]

This issue can cause all kinds of different runnability problems. Probably a good chance it was this issue or at least it was a contributor to your problems anyway. I may have just had a bad run of luck, but I'm yet to come across one that DIDN'T have this issue, so my view might be skewed on these saws haha

[@lucaskrist2877]

Hi Ben, any advice on removing the white plastic cover between the cylinder head and carb without removing the head? I am just trying to replace the coil. Thanks.

[@samishsawworks5870]

Are you concerned with removing it so you can remove the plug wire attached to the coil?

[@lucaskrist2877]

@@samishsawworks5870 exactly, it seems the boot for the spark plug is too big to pull the wire out through that plastic piece.

[@samishsawworks5870]

@@lucaskrist2877 so, instead of trying to pull the boot "down through" think more of pulling the plug wire "out through the side." The plastic partition has enough give you can pull the plug wire out through the side of you pry the plastic partition piece a little. If you email me [e-mail] I can send you pictures. I happen to have one here right now.

[@J.E.Taylor]

You probably already figured it out, but if someone else reads this and has the same question, you can pry that plastic baffle to the left to open up that channel to slip the HT lead out. Then ease the boot down through the plastic and out with the coil. The other method is to unscrew the HT lead from the coil. Coil comes out the side, HT lead with boot comes out the top. Either way is fine. This applies as long as your lead is threaded into the coil and not bonded in.

[@johnclarke6647]

Be careful - the chain break handle that came with my ms-250 kit was not machined properly. It had casting seams on the top and bottom on the handle leg that goes on the pin. This kept it from seating down on the case and the outside seam kept the support slide from fitting properly on the pin, so I left the support slide off because I coul not get it to fit on the chain break or dog bone pins. A mistake on my part. The chain breake worked for a while but it did not work fo long. The pressure on the chain break handle bent its pin to the rear and the dog bone pin, forward. I think I can straighten both pins and I have ordered a complete new set of parts for it. When it failed I failed in the “on” position. I had to completely disassemble the chain break system and then noticed the problem, a defective handle, so inspect these parts before assembly.

[@edwingroening5087]

Great video. I just tore apart an ms210 with a bearing failure on the pto side. Can you put an ms250 motor into an ms210 body?

[@samishsawworks5870]

Yup! They share the same chassis. Should plop right in, providing you're swapping the whole short block. If you're NOT swapping the whole engine, and you're just looking to swap piston and cylinder, I know they have different length stroke. Something to look into. Otherwise, slip that 250 engine in and let 'er eat!

[@edwingroening5087]

@@samishsawworks5870 oh right on! Appreciate it 👍

[@budifund928]

What is the number of T special tool to open the bolt of hand brake guard?

[@samishsawworks5870]

All the screws on this saw should be Torx T-25

[@budifund928]

@@samishsawworks5870 I got it today; T handle wrench with part number 5910 890 2400

[@J.E.Taylor]

T27 is the appropriate size although T25 will work if it's all you have and you're careful.

[@alikockaya76]

17:47 Could this be the answer to the question of what's causing those air leaks? Perhaps during assembly, they put on the sealent, then bolt it all down before it has time to dry?

[@samishsawworks5870]

It's gotta be something along that line, or one side isn't properly cleaned, or...... or....... whatever it is, it's an issue.

[@alikockaya76]

@@samishsawworks5870 The clamp all method just feels flawed to me. I think the header needs to be bolted separately instead of being attached with the body. Otherwise the body vibrations getting transferred directly to the header could cause enough gaps for the leak. Another reason to have seperate header bolts would be to have much better torque setting. I just can't see how everything could be torqued together, body, shell, plastic header & all. Just my two cents, cheers!

[@samishsawworks5870]

I couldn't agree more. The body has "steel sleeves" in it to keep it from compressing, but it's a piss poor attempt in my eyes. I think the bolts loosening has the biggest impact on these leaking. I'm yet to pull one apart that had bolts that were actually tight. Cheaply made, that's all there is to it.

[@kudalauthebat]

the cylinder cover is not easy to assemble and reassemble.

[@rudratreecuttingservice470]

Speyar ....?

[@simpleman4224]

More great info!👍👍👍👍🇺🇸🇺🇸🇺🇸🇺🇸🙏🙏🙏🙏

[@clydelandry6443]

P

[@gyulakruppai9500]

Ronda fejed van!

[@augustinkj7112]

Assembling video

[@davidcarberry3547]

ya i knew it those stupid plugs suck i have scars to prove it, im makin a tool

[@samishsawworks5870]

Every FREAKIN' time haha

[@davidchristie4218]

What symptoms did this leak cause?

[@samishsawworks5870]

Sporadic runnability. It had a bog right off idle. The idle wouldn't hold a tune. It would seem fine, then go rich all of a sudden and die. Adjust for too rich condition, it would idle okay then go lean and die. Hard to restart especially when hot. Like 3 or more pulls to get it to fire (usually I'd have to choke it) It would seem like it was tuned correctly on the high side for "an amount" of cuts, then just go lean in the cut out of nowhere. Basically it couldn't hold a tune no matter what.

[@davidchristie4218]

@@samishsawworks5870 thanks for the info. I'm picking up a 021 for cheap and previous owner states it stalls when hot. So here I am looking at KZbin trying to solve it before its even in my hands. Hopefully its something simple.

[@samishsawworks5870]

@@davidchristie4218 Could be any number of things of course, the easiest being the spark plug. I've had a run of bad luck with failing plugs lately. Not fouled, but actually not functioning properly. That's the easy one ;) Usually if it stalls when hot my first thought is it's a compression issue, next possible air leak or coil problem. Could also be a tank vent not breathing creating a vacuum in the tank and length of run time is just coinciding time wise with when the saws gets hot. Here's to hoping it's something simple. If they're okay with you pulling the muffler, it's just two 8mm (5/16") nuts to get the muffler off and look at the piston. Anyway, good luck! Keep me posted with what ya find ;) they're great little saws and easy to work on.

[@mattshaw6828]

Great video man, appreciate it. I’m literally doing a tear down on my 021 today as I need to replace the cylinder, so this is super helpful. Question for you. At 1:10 in your video, when you shine your torch in the muffler housing. Below the left hand bolt there is a small, round orange seal or plug. What is that? I don’t have one on my saw, it’s just a hole. What is the plug abs hole for? I’m baffled! Tuning in from Melbourne, Australia by the way. 🇦🇺

[@samishsawworks5870]

@@mattshaw6828 it's a plug. They commonly fall out. If it hasn't started yet, it will eventually be a giant oily mess. The hole is left over from the casting process I believe. It goes through to the "pressure side" of the oil passage that leads from the tank to the bar. There are lots of various fixes for it. Basically you can plug it with anything you see fit. The only thing is you can't go too deep with your plug as it will block the oil passage. If you have means to email, shoot me a message [e-mail] and I'll get you some pictures and such of what how to repair. If not I'll try and explain it on here.

[@bubpiper4028]

I have a Stihl MS250, that will not fire at all. MAGNETO is keyed correctly..... So, we have spark, (at the right time) we have compression (110 psi) exhaust ports are clear Carburetor has been cleaned twice Installed a new coil (even if it did not need one), it is spaced correctly All the coil grounding wires OHM correctly I tried 3 different spark plugs. Replaced the gas with fresh 2 stroke mix that works in other two strokes I have tried GUMOUT and Starting Ether (in the cylinder and carb intake) I spin the engine over with a drill, there is spark, but not a sign of gas igniting. The plugs look wet. GIVE ME A CLUE......

[@bubpiper4028]

In case anyone is interested... I removed the piston and it was melted on the exhaust port side. I sanded the aluminum transfer off of the cylinder and ordered a new piston and crankshaft seals. $8. It is on a slow boat from China... I cannot wait .....

[@bigfranksworld]

I have the exact same symptoms with an 025 I'm working on. Starts and dies. Hard start. fuel is getting there, spark is good. 125psi compression. Sometime will idle, but bogs when throttle is applied. Out of things at this point. Could use some help.

[@Davo996]

I really don’t get why people buy Stihl saws. They just constantly break down. I’ve got a husky 45 rancher/ it can handle any size hard wood is light has never broken down once in 30 years.

[@michellatour150]

That red RTV doesn't look original, too sloppy as well to be factory applied, most likely from a past teardown. Actually not the right product to use in such applications as most RTVs are not 'gasoline resistant' like a Motoseal, Hondabond etc. type case sealant, likely a contributor to the air leak.

[@nm6405]

Hard to say...stihl uses dirko which is red, so it might be

[@vladgor4418]

Next time your hat throw in the garbage many traffic.

[@viperstrike3827]

???