Stihl 025 stalling at idle.. Impulse? Crank seal?

[schmauster]

Very often after a cut I let the 025 idle and it stalls out after a few seconds. Runs great but at idle it stalls like crazy. Ive had it tuned and always run fresh gas with the correct mixture. Recent air filter, fuel filter, spark plug, inspected spark arrestor (had the same issues before) It seems to be related to movement of the saw (swinging it around or shaking it at idle) It seems to have gotten worse over the year ive had it... its super aggravating. After stalling it sputters back to life fairly easily with 2 or 3 pulls.


Today I removed the fuel hose and checked it very thoroughly for cracks. I verified the carburetor is clean and tight with a good seal. The gaskets look great. Upon removing the pull starter to verify the coil gap to flywheel I noticed it has a lot of dark sawdust built up inside the cover.. The flywheel was very clean but all around it and especially right behind it there is a lot of wet oily junk. I scraped a lot of crap from the area but you get the idea. Ive heard leaky crank seals are common on 025s. I tried to wiggle the flywheel to check for excessive clearance and it seems tight so i dont think much if any damage has occurred yet.

Ill be replacing the impulse hose (ugh) when i get it as its a likely an issue or soon to be... I just dont want to roast my bearings and cause other issues with a leaky crank seal... I really enjoy this saw and cant afford another one anytime soon

Heres a few pics of the oily carnage

 

[Country bumpkin]

A lot of times on that saw when you pinch the saw & twist it around the impulse line can become loose at the handle housing. You can take the handle off & get in there with needle nose pliers to check it. I fixed on with idle issues for a boy that the crank seals were bad. They're known for that issue. The gum & dirt behind the recoil is normal. I use purple power to clean mine up. Hope that helps ya some.

 

[a. palmer jr.]

Some people try to run the idle too low on a chainsaw, should be low enough that the chain doesn't move but not much lower.

 

[lone wolf]

Rip it down clean it and test the vac and pressure.Otherwise you could be just wasting more time.

 

[HarleyT]

Have you rebuilt the carb yet?

 

[schmauster]

The idle was set last time i had it tuned not long ago.. The carb looks perfect inside, no residue at all. Ill do a vac/pressure test on it and report back. Thanks guys

 

[lone wolf]

The idle was set last time i had it tuned not long ago.. The carb looks perfect inside, no residue at all. Ill do a vac/pressure test on it and report back. Thanks guys

Pressure test the carb, fuel line, impulse line too. I will take a wild guess a crank seal is leaking.

 

[a. palmer jr.]

Kinda difficult to change the seals on an 025, if that's the problem, have to pretty well take everything apart..

 

[schmauster]

Rip it down clean it and test the vac and pressure.Otherwise you could be just wasting more time.

Cleaning and disassembly is happening as I have time. Took purple power to it in the bathtub and showered it off with hot water. (Wife didn't mind :O she's a keeper)
Been super busy lately but it's been raining a lot here in northern California so it's a good time for this

Have you rebuilt the carb yet?

Could be a stiff pump diaphragm maybe. I run 91 w/ethanol mix Cali fuel. The saw has some hours on it. Don't think it's been used daily but I'm sure it sat with fuel/stabilizer for a long time. Carb looks perfect inside from initial inspection. Haven't felt the diaphragm. Been wrenching quite a few years on cars and 4stroke motorcycles. Im fairly new to 2strokes. Been reading a lot on here in my idle time slowly absorbing info.

Pressure test the carb, fuel line, impulse line too. I will take a wild guess a crank seal is leaking.

Changed the impulse line just because it was a pain and in question. The old one looked fine upon close inspection unfortunately. I'm leaning toward the crank seal also at this point. I figure I'll do both if one tests bad. I've ran this saw for a while as it is (stalling at idle) it was recently tuned so I'm guessing that's why it hasn't grenaded yet with the seal(s) leaking. Should I open the motor up to inspect bearings and delete the head gasket for higher compression while I'm in it this far? (If crank seal is leaking) Piston looks great through the ports but i want this saw to be around a long time if I can help it.

Kinda difficult to change the seals on an 025, if that's the problem, have to pretty well take everything apart..

That's OK at this point. I just want this thing to be a runner for years to come. Was given to me by family and money is tight for now.



A little back story if anyone cares since I'm guessing I'll be around posting for a bit. Learning from the pros...


New to the forums here. people seem friendly and helpful. Nice site you have here. I've worked for a tree service dragging brush and pulling lines for a few years. Split a bunch of wood for family and friends in the past. Worked clearing trails and cleaning up properties for a few years too. I've stepped it up a little, now I'm doing the odd jobs cutting up trees laying in roads and other little things for friends. Got an old workhorse 8hp Montgomery Ward wood splitter for 500. The guy I got it from had a machinist friend that made it for him. It's a little rough and needed some love. Runs great now and splits anything i can lift into it. Lately I've been given the two saws in my Sig and learning as i go.

Thanks guys!

 

[Country bumpkin]

Yes you'll have to disassemble it but it's easy to do & seals are cheap. Use some dirko red sealant or permatex motoseal or any 2stroke case sealant & you'll be fine. Just remember the clutch is reverse threads. I use a rope stuck in the spark plug hole to lock it for me. Take your time & take ya couple hours going slow. Hope that helps.

 

[schmauster]

I wasn't sure where to post this maybe you can advise.

I used a friend's 200' 1/4 inch steel braided cable for a bunch of dragging work along with my snatch block. Dragged some huge oak rounds out of the road after cutting it up. Grabbed some old trees out of the bush also. Definitely something I want to add to my gear. I priced the 200ft 1300lb cables around 200 bucks. Didn't seem too horrible for a dollar a foot.

After thinking about it more I figured I would rather have a used wench for likely a little more.. then I could mount it to a reciever for the tow package in the rear so I can easily detach when not needed. I don't do much 4x4 unless it's to get firewood.

I don't know how much pulling capacity is needed for our 2000 4runner 4x4. I think the car weighs a little under 4000lbs with close to stock size tires.

Like I said previously I'm pretty new to this. I'd rather get something a little over rated than something that will leave me needing more later. Any advice?

 

[schmauster]

I found some wood dust in the breather side of the fuel pump diaphragm I think. Doesn't seem too odd, just don't remember it being in there last time I opened it up. The diaphragm is super soft but I have a rebuild kit coming for it anyways.

The side pictured was facing up away from the carb internals. The other side was perfectly clean.

 

[schmauster]

The flywheel side seal was leaking. Also the bearing behind the flywheel was a little rough. Got some new eBay seals and bearings. The 025 didn't have a base gasket to delete unfortunately.

I tried some heat on the bearing and a puller and it's on there pretty good. Worried about getting the crank to hot. I'm going to get a better puller from AutoZone.

 

[Finnrpm]

Hi there!

Remenber to check that intakeboot really good, i overlooked that and ended up doing whole thing again....
I used coldspray to loosen the crank from the bearing and when installing bearings i kept the crank in freezer overnight, so the bearings installed just by pushing, no hammer needed.

A toothpick is a good " tool " to get the new seal over the circlip groove on the clutch side.
RV

 

[pioneerguy600]

Get the bearing separator type like we posted in your other thread. They are specifically designed to pull bearings off shafts.

 

[Wood Doctor]

I fear that the seals on clam shell engines were almost designed to break down. When that happens, they both have to be replaced. Yes, it's a PITA, and the clam shell design almost breeds it. Stilhl dealers have probably kept mechanics in business for years rebuilding clam shell engines that stop dead when the crankshaft bearing seals break down. The professional series Stihl saws are much less prone to crank seal failure.

Sometimes the bearings give up along with the seals and will even throw balls right out of the races. Most of the time just the seals give up and the bearings are OK. But, regardless, the engine has to be torn down to replace the seals and you will have parts all over the place. The air leak that results from a ruptured crank seal makes it impossible for the carburetor to deliver a fuel mixture to the combustion chamber because the carb loses the signal from the impulse hose. So, the engine will not start and run continuously.

Strangely, enough, this crank seal failure can happen when the engine still has excellent compression, a good spark, a perfectly good carburetor, new fuel lines, a good fuel filter, etc.

 

[SteveSr]

Yes you'll have to disassemble it but it's easy to do & seals are cheap. Use some dirko red sealant or permatex motoseal or any 2stroke case sealant & you'll be fine.

I just fixed the same issue on the same saw. There are two different seal part numbers depending on if you will be splitting the case. Be sure to get the right ones. These saws like to leak at the junction of the seal and casing halves. You need a gap filling and hardening sealer... like the Dirko to fill and seal these gaps. The current formulation of Motoseal doesn't do this and caused me an issue so I went and got the Dirko. There is a whole thread on this just search for posts by me and you should be able find it.

 

[Wood Doctor]

Hi there!

Remenber to check that intakeboot really good, i overlooked that and ended up doing whole thing again....
I used coldspray to loosen the crank from the bearing and when installing bearings i kept the crank in freezer overnight, so the bearings installed just by pushing, no hammer needed.

A toothpick is a good " tool " to get the new seal over the circlip groove on the clutch side.
RV

'Tis as shame we can't slow this down 80%. Then it would be a valuable video. People must drive rather fast in Finland.

Oops, I guess there is a way to drop it down. Use the settings control and change the speed to .25. That helped a little.

 

[schmauster]

I bought some yamabond 4. Any idea if this will work? I'll mic the seals and see if I've got the right ones. Thank you. You probably saved me some costly downtime

 

[cus_deluxe]

Yep thatll work. I use permatex anearobic gasket maker available at my local napa. Less is more, just make sure to put sealer all the way around the outside part of seal itself as well as the cylinder/engine pan mating surface