Stihl MS 291 burnt out after 1 hr

[MaineMikeD]

Whew, that is one ugly piston/rings...could the saw have been straight gassed? If not, there has been a big air leak or way too lean carb for quite a while.

There isn’t a chance in this world that saw had straight gas unless the dealer did something that stupid while “fixing” it one of the times they had it. This saw was barely run, and only had premix 50-1 which is what the manual called for.

 

[blsnelling]

Straight mix or air leak. Pressure test it and find out.

 

[MaineMikeD]

Straight mix or air leak. Pressure test it and find out.

The images weren’t visible in the links. Do you recommend a pressure test kit?

 

[a. palmer jr.]

A fellow brought one of those into our local shop wanting it rebuilt. It had a piston like that. Customer said it wasn't in warranty since it was used professionally and he didn't want OEM. I checked and couldn't find any aftermarket parts for that saw at the time. This was about a year ago if I remember right..

 

[a. palmer jr.]

If the piston looks as bad as that one I don't pressure test them, I just rebuild them and replace or check everything that could leak.

 

[jr27236]

There isn’t a chance in this world that saw had straight gas unless the dealer did something that stupid while “fixing” it one of the times they had it. This saw was barely run, and only had premix 50-1 which is what the manual called for.

So in my opinion that severe of scoring and the dryness of that piston is more of the most recent catastrophic failure. I would be looking at the carb boot for a tear possibly? Also wonder if the genius at the dealer retuned the carb and leaned the hell out of it. Either way your out of warranty and I'd pull the carb limiters and see where the screws are at (do you know how to do this?).

 

[MaineMikeD]

So in my opinion that severe of scoring and the dryness of that piston is more of the most recent catastrophic failure. I would be looking at the carb boot for a tear possibly? Also wonder if the genius at the dealer retuned the carb and leaned the hell out of it. Either way your out of warranty and I'd pull the carb limiters and see where the screws are at (do you know how to do this?).

I bought a Husqvarna 455 so I might just strip the MS291 down, and sell what I can, and never buy Stihl again. I appreciate everyone’s efforts on this site helping me (or trying to). If the Stihl reps that I interacted with acted like that maybe I wouldn’t be as pissed.

 

[MaineMikeD]

I bought a Husqvarna 455 so I might just strip the MS291 down, and sell what I can, and never buy Stihl again. I appreciate everyone’s efforts on this site helping me (or trying to). If the Stihl reps that I interacted with acted like that maybe I wouldn’t be as pissed.

Just to be clear I would be selling the bar, non-engine components, etc. Obviously, nothing that could be damaged... Or I might just throw it on eBay as a scored piston parts saw...

 

[jr27236]

I bought a Husqvarna 455 so I might just strip the MS291 down, and sell what I can, and never buy Stihl again. I appreciate everyone’s efforts on this site helping me (or trying to). If the Stihl reps that I interacted with acted like that maybe I wouldn’t be as pissed.

455 is a nice saw. I would use the 40:1 mix just for some extra lube. As for the Stihl rep, I get why they said what they said and I believe it was NOT just the damage but the time. It was out of warranty and after that time frame and the damage at hand they were never gonna do anything for it. I would be angrier with the dealer, they are the ones who couldnt properly diagnose the on going issue from the start. Hate to say it but Husky will do the same thing im sure if all the circumstances were the same. Good luck with your new saw. Just sell the old one complete and be done with it.

 

[userx]

Our 028AV crapped the bed after 30 years of dedicated service. My father bought a brand new MS 291 to replace it. This thing was terrific for 1 hr of use, and then on the second outing, about a month ago,I was bucking up a fairly large spruce. After I felled the tree, I worked the saw pretty stead for about 10 minutes limbing up and cutting the trunk into 16" lengths. I had the saw pretty well buried into the lower trunk when I start to see smoke coming out around the bar area. This whole time the chain had been moving, the brake was off and there were no signs of any problems.
First I check the bar oil (check) and chain brake (0ff). The chain tension was just fine, but there is a lot of resistance when trying to rotate chain by hand. So I rip into it and find a bunch of burnt up plastic around the sprocket area. It goes without saying that there was OEM Stihl two stroke properly mixed in the gas. I mean this is a brand new saw. So I send it over to my dealer who we originally purchased it from and wait. A month later they come back and say Stihl won't cover the repairs. Stihl claims that I was overreving the saw with the chain brake engaged. Are you kidding me? I've been running Stihl saws since I was 12 and there is no way this is the case.
The estimate for the repair is $541.90 so the saw is basically an assembled inventory of parts that is quite worthless to us. Parts that would need replacing are the chain sprocket, needle cage, worm gear, oil pump, engine housing, various oil seals, the brake band and the clutch.
So as of now my father is out about $500 while getting 1 hr of use out of this brand new high end saw. Stihl just doesn't make 'em like they used to (I ran an 031 and a 1970's 041 farm boss for many years without incident) and I feel that they obviously don't care about retaining customers after this experience. I'd love to hear others' theories on what might have happened, because Stihl's version is not what happened. I am going to call Stihl directly on Monday and try to work this out because I think there was some sort of internal failure that caused this overheat. I will post updates if there is anything to update.

One thing I want to be clear on is that my local dealer did everything they could to try to get this covered for me, but in the end Stihl made the decision not to cover it.

Pictures to follow.

West041, I have a feeling it is not the sap. The same thing happened to me after the first weekend with the new saw, Stihl MS 271. It was last fall and I was running the gas out of it to store it up for the winter. It was sitting and idling and only running about 3 to 5 min (I had walked away to fumble around in the garage) and when I glanced at the saw it was smoking like crazy at the bar. Took it into the dealer and they said I left the chain brake on while revving it. I told them it was on idle and when I looked in the manual it specifically said chain brake can be engaged on idle. Anyway, it melted and I lost the pins, the oil pump melted to the housing, the housing plastic was melted and I can't seem to find a replacement housing as of yet. I have rebuilt two chainsaws since and before I attempted to fix this one. Unless I find a new housing (I believe it includes the oil reservoir as well) then I am stuck with using this as spare parts and buy another new chainsaw. I was out $400 plus, stihl wouldn't cover it and I really don't think my dealer did much at all to fight for my warranty. I will never go back to that dealer for any repair work. I will not buy another Stihl unless I hear they addressed this issue. I am doing all small engine repair myself now that I feel I was taken to the cleaners on this one. It is very frustrating and I firmly believe there is a design flaw in these new Stihls.

 

[a. palmer jr.]

I bought a Husqvarna 455 so I might just strip the MS291 down, and sell what I can, and never buy Stihl again. I appreciate everyone’s efforts on this site helping me (or trying to). If the Stihl reps that I interacted with acted like that maybe I wouldn’t be as pissed.

No reason to never buy another Stihl again, just be careful which model of Stihl you buy. Some of the old saws that end in an even number are okay, like the 026, 044, 660 etc. are fine saws...I probably wouldn't take a 291 if someone were to give me one...

 

[HarleyT]

So you left a saw idling alone with the chain brake on to run out all of the fuel, and it revved higher as it ran out of fuel, and melted down the saw, while you were not there?

And this is Stihl's fault?

 

[HarleyT]

How could they address this issue?

 

[userx]

How could they address this issue?

thank you, yes, there seems to be a flaw in the writing there. However, the gas never got far enough down to even be close to revving up the idle. The idle never made a difference in sound to my ears, such as an increase in idle from whence it began. Again I fumbled around for 3-5 min. I do not blame me, so why wouldn't it be stihl? And to remphasize, the manual states that the chain break can be engaged on idle. Nowhere does it say that it can idle for only a certain amount of time. Although, I will keep your comment in the back of my mind for future operations.

 

[opinion]

The chain brake can be engaged at any time. The master control switch has no bearing on it. What you did was have your switch on throttle lock with the chain brake engaged assuming it was on idle.

 

[HarleyT]

Well, at any rate, the clutch was engaged, causing the heat. Meaning that if the brake was not engaged, the chain would be turning. And if the chain was turning, then your idle was set too high.

 

[userx]

The chain brake can be engaged at any time. The master control switch has no bearing on it. What you did was have your switch on throttle lock with the chain brake engaged assuming it was on idle.

thank you. Maybe there is something I do not understand in your statement, but not sure how I would have had it on throttle lock and think it was idle. This was a new machine and neither the throttle trigger or the lock was sticking. I certainly understand that the chain brake can be engaged anytime; and I understand why it shouldn't be when pulling the trigger. Unless the manufacturer had the idle set too high, I don't see how this could have happened. And no, at the time I had not taken the cover off to see if there was an issue with the throttle nor would I have any reason to adjust the idle.

 

[Andyshine77]

It's clear in most cases the high idle had been set and the saw was allowed to run with the chain break on. The idle would have to be way off for this to happen, unlikely. It's possible the throttle was stuck open a bit, but unlikely. The simplest most obvious answer is usually the correct one. This also happens quite often.[emoji111]

 

[stilh036prohog]

What you did was press the brake handle a wot while cutting, that's all. Not fully engage the brake by locking it forward but merely apply some pressure on it while cutting and when saws operate at 8-10k rpm it don't take much to generate too much heat. You need to read this so you are contious of this and don't repeat the mistake. l consider myself experience with saws and l have done this while trying too cut stumps low to the ground, however without the results you got. I cannot believe after 19 pages nobody has considers this, its not that hard to work out what happened.

I don't think the brake was on,just leaning on to much. You can do it with an 041 not the clamshell's. I have seen this many times. Yeah it will a new seal

 

[stilh036prohog]

Is everyone in agreement that the clutch springs probably got cooked and the clutch needs replacement? I've never cooked a clutch before so I don't know.

Yes