EXPLODED IN FIRE! Stihl MS 291 18"

[docdoc]

I bought an MS 291 18" from Ace Nov 27th, 2021. I used it (until TODAY) solely to cut saw mill cut offs (about 8ft in length and many varying thicknesses) I got off a local Amish sawmill that makes slats for wooden pallets.

Well, today, I had the saw running after a cold start and letting it warm for a bit. Then, when I tried running it (turned safety off) all of the sudden . . . BANG! An explosion of fire from the bottom side of the saw, and the chain will NOT stop when I but the brake back on. I took the cover off, and there are metal strips sticking out. One melted into the housing of the saw, and the other just sticking out. Looks like it was a metal strip or spring that was wrapped around the rotating part of that turns the chain (around the edges of whatever you call this thing, inside the plastic housing).

Clearly, something busted. What did I do? What happened? This thing looks shot, and now over a year of personal use, the warranty ended last November.

Here I thought I'd have this trusted brand chain saw for years, but it lasts just about a year and . . . . BOOM!

Anyway, if you experts out there know better, please let me know what happened? My fault? Defect?

Thanks!

 

[KostasVolos]

The brake spring is totally destroyed .As also the casing around the clutch /drum .
Looks like the brake was engaged
while the chainsaw was operating at WOT ( wide open throttle ) or the clutch was engaged (due to high rpm while idling ) while the brake was on ,
while the saw was warming up .
There can be other explanations ,I guess ,like solidified oil ,debris or resin accumulation between brake and
clutch drum ,for example.

 

[docdoc]

Ugh - so, stupid questions (and maybe expensive mistake) but when you start that puppy cold, you need to put it on the choke. I think what I did was here:

https://practicalmechanic.com/2020/04/04/how-to-start-a-stihl-ms291-chainsaw/
Between steps 8 and 9, I would let it run for a minute or two (thinking it was "warming up the engine").

From what you just said, and knowing how step 8 "sounds," I think I f$#%*&d myself on this thing, eh?

Beyond that, any chance this thing can be repaired, or too expensive that it's just easier to buy a new one?

Thanks again!

 

[snobdds]

Yep, brake band on while saw is running at high RPM.

Friction causes heat which causes fire.

 

[docdoc]

Yep, brake band on while saw is running at high RPM.

Friction causes heat which causes fire.

Thanks - learned the hard and expensive way (but fortunately not at a cost to my physical body - just my pride and emotions - a lot of household items are failing at once here - this was LEAST expected).

Anyway, I think I get it now that the safety is a "brake" and not a "disconnect" like my electric Oregon. Now I see it's like revving the engine of my car with both gas and brake pedal pressed to the floor at the same time while the gear is shifted into drive - not a healthy practice!

DANG! Live and learn . . . . but, is it repairable? Would it even be worth the repair?

 

[KostasVolos]

For better or for worse ,personally
I never start my saws with the chain brake on ( but I never "drop start " my saws ) .I use the brake only when I leave the saw idling somewhere besides to move a log or any other job that needs both my hands .

It can be repaired ,of course .
New brake and case and probably an oiler worm gear,too.
You can order them either as after market parts and install them yourself or
have someone with a bit more knowledge to do it ( the relatively cheap way ) or take it to a Stihl service and have the OEM parts ordered and installed ( the expensive way ) .

 

[docdoc]

For better or for worse ,personally
I never start my saws with the chain brake on ( but I never "drop start " my saws ) .I use the brake only when I leave the saw idling somewhere besides to move a log or any other job that needs both my hands .

It can be repaired ,of course .
New brake and case and probably an oiler worm gear,too.
You can order them either as after market parts and install them yourself or
have someone with a bit more knowledge to do it ( the relatively cheap way ) or take it to a Stihl service and have the OEM parts ordered and installed ( the expensive way ) .

OK thanks - maybe I'll take it back to Ace and see what they have to offer first. I'm not afraid to "tinker," but I definitely don't know what I'm doing, so I would need to find a video guide that walks through the EXACT steps of a matching unit, clearly spelling out what needs to be done.

Thanks for your insights!

 

[KostasVolos]

Doing it by yourself might not be so easy .For example ,removing the oil pump from the old case and installing it on the new one is not an easy task . As also there are few other that are kinda complicated enough ,if you lack the experience and/or expertise,like removing the clutch,
removing and reinstalling the flywheel ,adjusting the ignition gap ,etc .

 

[docdoc]

For better or for worse ,personally
I never start my saws with the chain brake on ( but I never "drop start " my saws ) .I use the brake only when I leave the saw idling somewhere besides to move a log or any other job that needs both my hands .

It can be repaired ,of course .
New brake and case and probably an oiler worm gear,too.
You can order them either as after market parts and install them yourself or
have someone with a bit more knowledge to do it ( the relatively cheap way ) or take it to a Stihl service and have the OEM parts ordered and installed ( the expensive way ) .

Looks like this: https://www.ebay.com/itm/363694083355
And this: https://www.ebay.com/itm/Oil-Pump-O...1-Chainsaw-1141-640-3203-/323872042633?_ul=IN

Would you agree?

 

[KostasVolos]

Looks like this: https://www.ebay.com/itm/363694083355
And this: https://www.ebay.com/itm/Oil-Pump-O...1-Chainsaw-1141-640-3203-/323872042633?_ul=IN

Would you agree?

Yup !

And one of those :

https://www.ebay.com/sch/i.html?_nk...MIh9Tw0fKu_QIVELvVCh3hyARDEAMYASAAEgLTifD_BwE
( crankcase/oiler housing )

 

[firescout]

For better or for worse ,personally
I never start my saws with the chain brake on ( but I never "drop start " my saws ) .I use the brake only when I leave the saw idling somewhere besides to move a log or any other job that needs both my hands ...

Same here. Been doing it that way for 40-something years with the larger (50cc+) saws. They're teaching the new guys (fire dept.) to apply the chain brake before starting all saws. The only saw I occasionally drop start is an Echo CS-355T, when trimming up in the tree.

 

[stihltech]

Chain brake on when starting, yes. What they don't say enough is to get it off fast idle or release the chain brake right away.

 

[docdoc]

Chain brake on when starting, yes. What they don't say enough is to get it off fast idle or release the chain brake right away.

Yes sir! I understand the mechanics of it now (and watched quite a few videos since as a result of all the helpful people here).

Fully guilty as charged! And here, I thought I was doing a “good thing” by letting the motor “warm up” before taking brake off. I didn’t know it was a brake. I throught it was more like a transmission (meaning I thought the gear was disengaged).

Stupid!

But I shall attempt a repair with the $130 worth of parts I found, direction from the good people here, and good old YouTube how to’s (there’s one out there about “Jr.’s bad day,” and is hilarious—guy does the whole video with hillbilly fake teeth in his mouth—but it’s very helpful).

 

[Up A Creek]

You're only stupid if you don't learn your lesson. Everyone on here that knows what they're doing has loads of stories of mistakes they've made.

This may have already been said, but I suggest buying the clutch tool and a (plastic) piston stopper vs pliers and stuffing something in the cylinder. You may be able to find a generic spanner wrench that will fit the clutch, but personally I like having the correct tool. Less chance of slipping. The clutch is LEFT HAND THREAD. It theads off and on BACKWARDS.
I've had pieces of rope fibers break off in the cylinder. Makes extra work.
So much less hassle and chance for breaking something.
Speaking as a mechanic of 25 years. I've done half ass and backyard fixes. There's a time and place for them, like out in the field or in an emergency, just not when you're at home trying to fix something so it lasts IMO.

The engine will only turn in one direction because of the starter assembly. If you remove the starter cover the engine will spin easily in either direction.

Before you break the clutch loose make sure you understand which direction the piston is going, so that it will push against the piston stopper. Also make sure the piston is tight against the stopper (in the direction you want) before you apply a lot of force.

 

[leaf]

Yuh, you may be lucky and just turn the clutch "left" (meaning the threads are "left-hand," rotate clutch right as seen from outside), as noted, and it will rotate off just as neat and sweet as can be. On the other hand, torquing it that hard AND getting it that hot may very well have made, as a practical matter, a "jam" of no small order and effect (between clutch and crankshaft). In the world of life as lived through chainsaw mechanics there are several "techniques" to un-jam the jam. Most of the best methods are not hyper "force-ful" (like putting a "fork" tool on a one inch impact gun and just banging against that piston stop, etc.). You are going to have a new clutch. Relief cuts in the old one, for instance may, just may, be part of the way you un-jam. Obviously, save the threads on the crankshaft at all costs.

FWIW it just may be that well-adjusted brakes are a really good safety approach to the risk of having the saw pop up into your face, BUT it may be better, as some people do, to treat ANY saw that is running (or starting -- leads to running) as something you don't get near the bar / chain of, rather than be one of these people who are turning the brake on and off and on and off constantly, (and then sliding the saw across their thigh ... because, well, the brake is on... or... they thought it was...)

 

[rarefish383]

My local shop showed me a brand new Stihl, it was bigger than the 291, but I forget what it was. Similar results. My buddy, the mechanic there, asked if I had ever seen anything like it. I said yeah, the homeowner started the saw and let it set warming up, then grabbed it and forgot to release the chain brake and kept holding it wide open, till it forced the chain to go. It got so hot it turned the clutch drum and the back part of the bar purple. It also got so hot it melted the case through around the crank that the case was ruined. No idea what happened to yours, but forgetting to release the brake can melt them. Just a side note. I have an MS 290 that is my truck saw. It stays on the back where anyone could grab it. It's so faded it's not even orange any more. I've been waiting for it to die so I can rebuild it with a 390 top end. it just won't die. I've had my MS170 since before I retired, 7 years ago. The 660 has done nothing but milling for about 15 years. I literally expect my Stihls to last the rest of my life. Usually when something like you described happens, I blame it on driver error. I admire you for asking if you did something wrong? Hopefully you never experience anything like it again.

 

[sean donato]

My local shop showed me a brand new Stihl, it was bigger than the 291, but I forget what it was. Similar results. My buddy, the mechanic there, asked if I had ever seen anything like it. I said yeah, the homeowner started the saw and let it set warming up, then grabbed it and forgot to release the chain brake and kept holding it wide open, till it forced the chain to go. It got so hot it turned the clutch drum and the back part of the bar purple. It also got so hot it melted the case through around the crank that the case was ruined. No idea what happened to yours, but forgetting to release the brake can melt them. Just a side note. I have an MS 290 that is my truck saw. It stays on the back where anyone could grab it. It's so faded it's not even orange any more. I've been waiting for it to die so I can rebuild it with a 390 top end. it just won't die. I've had my MS170 since before I retired, 7 years ago. The 660 has done nothing but milling for about 15 years. I literally expect my Stihls to last the rest of my life. Usually when something like you described happens, I blame it on driver error. I admire you for asking if you did something wrong? Hopefully you never experience anything like it again.

I was given a stihl 390 with a roached top end with practically no time on it. Have no use for it. You want it?

 

[rarefish383]

I was given a stihl 390 with a roached top end with practically no time on it. Have no use for it. You want it?

No thanks, I can’t kill the 290. Sometimes I think I should get rid of 50 or 60. It’s hard just keeping a few tuned and running.