An odd one... 391 pullcord ran out and muffler shook loose...

[sliceoflife]

So here's an interesting one. Not my saw. One of my in-laws friends is cutting up some logs on my property for firewood. He has a stihl 391. So he knocked on my door shortly before sundown... says the saw stopped on him... the pullcord had unwound itself and the muffler had shaken loose... now the pullcord is all the way out and not retracting. I didn't want to poke around with someone else's saw trying to diagnose...he's gonna take it into the mechanic to have it looked at... but it was such a weird way to die, I was curious if anyone knew what might have happened.

 

[rogue60]

So he's taking it to a mechanic...
When you see him next tell him to hand in his man card it's been cancelled!

 

[sliceoflife]

He's a bit older than me; cuts up firewood for himself as well as a side gig for the exercise. I don't think he really cares about the saw/tinkering aspect of things; just needs the saw to break logs down small enough he can use the splitting maul.

I Probably should have offered to at least open it up for him; but I'm not confident enough in my tinkering to work on other people's saws. Figured it'll either be a muffler screw fell in the cylinder and top end is trashed (Dont think that explains the cord being stuck out tho), or muffler screw fell in the flywheel and caught on something that broke up the recoil/starter...

But that's just based on his description of the saw dying in use; and him noticing the pullcord was all the way out (and saying it had retracted properly when he had started it) and briefly looking at the saw with the muffler hanging off; and the pull cord fully out.

I could probably do a starter/recoil assembly replacement for him if that's what it needs; but top end I haven't messed with pulling/replacing on any of my saws yet; I'd probably suggest he take it to the mechanic anyway.

 

[northmanlogging]

the pull cord mechanism gets gummed up with dust and goobers, or the spring broke, generally though they just get dirty and wont retract, or the dogs broke and jammed. fairly easy fixes
Muffler falling off is just a matter of tightening a couple few bolts, should be 2 inside the muffler and 4 on the outside, the 2 internal ones can be difficult to spot, they are in pretty deep and generally everything is covered in soot so hard to see if ya don't know what yer lookin fer.

as for man cards, not everyone should be turning wrenches, some folks are self aware.

 

[northmanlogging]

also, its highly unlikely that a seized motor via swallowed screw or some other oddity effects the starter retract mechanism, as its divorced from the engine after starting, has one or 2 cheap plastic dogs that cam out and engage the flywheel only if the starter cord is pulled, otherwise its designed to retract and never contact the moving parts again, but if its gummed up, it can stay engaged... which is why the little plastic dogs are cheap and easy to replace.

 

[rogue60]

as for man cards, not everyone should be turning wrenches, some folks are self aware.

Really even with something so basic as a couple of bolts and a spring? Omg the muffler even fell off so how hard would it be to have a look at the melted piston through the exhaust port after being straight gas?
I'm betting you save many thousands a year maintaining and fixing ya own gear and that’s even being unqualified for tuning wrenches... You should not be doing that and taking ya stuff to a clueless mechanic (oh hang on I mean "Tecnishon") which seems all to common now day's... are you not self aware?.
I mean don’t get me wrong I get it.. like for example I'm not qualified to change a light bulb so I get the wife to do that.
I better add I mean no disrespect to the op he seems totally capable of trouble shooting what's wrong with the above chainsaw.

 

[northmanlogging]

Really even with something so basic as a couple of bolts and a spring? Omg the muffler even fell off so how hard would it be to have a look at the melted piston through the exhaust port after being straight gas?
I'm betting you save many thousands a year maintaining and fixing ya own gear and that’s even being unqualified for tuning wrenches... You should not be doing that and taking ya stuff to a clueless mechanic (oh hang on I mean "Tecnishon") which seems all to common now day's... are you not self aware?.
I mean don’t get me wrong I get it.. like for example I'm not qualified to change a light bulb so I get the wife to do that.
I better add I mean no disrespect to the op he seems totally capable of trouble shooting what's wrong with the above chainsaw.

Not everyone was born breathing 2 stroke smoke and sipping diesel. We all have different strengths and interests, dude might be a wizard with jet engines, doesn't mean he understands piston engines.

 

[rogue60]

Not everyone was born breathing 2 stroke smoke and sipping diesel. We all have different strengths and interests, dude might be a wizard with jet engines, doesn't mean he understands piston engines.

C'mon man we all know working out what all the buttons do on the TV remote is harder than working on industrial two strokes

 

[Overlooker]

C'mon man we all know working out what all the buttons do on the TV remote is harder than working on industrial two strokes

I'm sure I don't use more than 15% of my cellphones features, because I'm just not that smart...or motivated! O

 

[Gord404]

ya well love wrenching but never have done my own taxes cause I dont care to learn about doing them- been wrenching all my life cause I like doing it... be out of business if everyone liked wrenching saws- very few do.

 

[sliceoflife]

Yeah, not my place to judge the guy's willingness to do the work himself... just a guess: like I said cuts his own wood for the exercise; not for financial or interest reasons and just would rather pay a mechanic than do this kind of work himself.

He may come back tomorrow depending on weather to haul some of the stuff he cut. If he does, I'll offer to show him how to take the flywheel cover and muffler off and do a quick diagnosis if something's obviously wrong.... maybe save him some time and money if it is something simple like a spring or dog broke.

 

[lwmibc]

FWIW--I took a chance and bought a Sachs-Dolmar 111 off CL a decade ago for $50; guy said he lent it out and it wouldn't start anymore. I saw that the two main Allen-head muffler mounting bolts were missing, the third one on a little tab on the bottom was all that was holding it in. Gave the seller the 50 bucks.

Took it home and removed the muffler; muffler gasket and heat shield were missing, piston showed striations through the exhaust port. Plastic bits for the chain brake on the right side were melted.

Removed the cylinder and piston. Exhaust side of the piston had suffered some melting, aluminum transferred to the cylinder wall above the exhaust port, ring seized in the groove on the exhaust side.

I ordered new ring(s) (they come in a pair, this saw uses only one), muffler bolts, gasket, heat shield; US$11.35 including shipping. I removed the old ring, used it as a guide to file the slightly-collapsed ring groove back out to a free fit of the new ring. Polished the side of the piston smooth again on a belt grinder that I use for knife sharpening, finishing with a leather strop belt. Fitted the new ring, filing with a points file for just the right 'feel' of fit.

Then spent a week of evenings with the cylinder and crocus cloth while watching TV, taking that transferred aluminum off the cylinder wall until I got down to nice clean nikasil.

I put it back together and have been using it constantly for the last decade, my favourite saw; best power to weight ratio saw I have. A big advantage in the Cariboo up here is the removable plug to allow heated air into the carb chamber when sawing in snow; big improvement over my Poulan 3700's--I had to always use two of them, one sawin' one thawin'.

So 'muffler bolts missing'?--that's the memory it tweaked. Who knows... My assessment was that the borrower let the muffler fall off to the point that he lost the gasket and heat shield; found just the one short screw at the bottom and 'put it 'back on'. The missing gasket and heat shield allowed the exhaust side of the cylinder to overheat, partially melting the piston inside and the plastic bits to the right. Saw quit before doing 'serious' damage.

Pull cord hanging out?--no idea, unless he's not admitting he pulled on the rope when the piston was seized and broke a starting tab or dog.

 

[stihltech]

I have a hard time understanding that you have such inept techs in your area. Actually, I take that back. I do. Now that we have at least 3 other retailers in the area that sell saws off the shelf (no instruction, only Silver techs at SOME branch, that is why I am swamped.

 

[sliceoflife]

So update from guy whose saw it is...

Evidently the muffler had been loose awhile and he kept running it.

Mechanic told him it's a total loss... burnt up, bearings trashed, etc... from running it with the loose muffler, which caused it to overheat.

Gonna see if they gave him the saw back and if so I'll ask him if I can take a look, and worst case I can maybe pull some parts that weren't destroyed off for him to sell on eBay, but also get a look at exactly what damage it sustained.

 

[SteveSr]

So update from guy whose saw it is...

Evidently the muffler had been loose awhile and he kept running it.

Mechanic told him it's a total loss... burnt up, bearings trashed, etc... from running it with the loose muffler, which caused it to overheat.

Gonna see if they gave him the saw back and if so I'll ask him if I can take a look, and worst case I can maybe pull some parts that weren't destroyed off for him to sell on eBay, but also get a look at exactly what damage it sustained.

I'll bet air leak caused by loose transfer cover.