Brand new MS391 meltdown

[StihlsawuserMS361]

I take a dry wall screw, get the little tab lined up and pull it out. Take a Dremel or whatever you have and grind the little tab off. Put it back in.

@ZeroJunk
After looking over impulse / fuel lines with no sign of leakages, I pulled the muffler just to help decide on course of action.. Looks fantastic for a 20 year old saw. Passes the pull rope compression test easily. Ran saw on it's sides, as well as holding by the handle and idling etc. All good.
Took the carb apart, minimal fines on top of the diaphragm, flexible , gaskets not brittle. Reassembled, a tiny bit of what looked like some oil in spots. Saw no longer changes idle after the cut. Ran two tanks through it. Acts like it used to be when new.
My experience is mostly 4 barrel carbs, but I never in a million years would have imagined a Walbro 2 cycle carb would selectively change idle speeds at will.
Much thanks for your previous help.

 

[Stumpzero]

I just wanted to say that I did read this thread and I am infuriated at your dealer for letting the saw out the door with the idle that high. If you had bought a saw at a big box store I could understand this sequence of events, but I really would at least complain back at the sales manager as that idle was dangerous. Had you not melted it, I beleive the high idle would have caused someone to get hurt later on. Not everyone can ear spot proper idle and carb tuning. This is a crappy situation to be in.

By cosmetics alone, I did not see heat damage to your clutch side crankshaft seal.

This was my whole contention from the beginning, The low idle was set way to high on the saw. The second saw I purchased (exact same model) was also very high on Low idle with the chain spinning very fast with the brake off. I am a person who takes full accountability for my actions and in this case I feel it was not my faught the saw burned up. The dealer not only gave me one Ms391 with the low Idlle set two high but a second one as well. Stihl made their decision not in my favor. That is life. But this was a valuable learning lesson. Hurt my pocket but in the end I have a back up saw for my business and here in Florida storms happen all the time so they come in use one day for that as well.

 

[Chainsaw Pete]

This was my whole contention from the beginning....The dealer not only gave me one Ms391 with the low Idlle set two high but a second one as well.

So many motorcycle owners have had worse than abysmal service* from their dealer's service department that we call them stealers. Guess the moiniker may not be limited to mc dealerships.

*What qualifies? Getting your bike back in worse shape than when you dropped it off or with a dangerous condition that did not exist when it was dropped off (loose bolts that constitute a life safety issue).

 

[Wood Doctor]

So many motorcycle owners have had worse than abysmal service* from their dealer's service department that we call them stealers. Guess the moiniker may not be limited to mc dealerships.

*What qualifies? Getting your bike back in worse shape than when you dropped it off or with a dangerous condition that did not exist when it was dropped off (loose bolts that constitute a life safety issue).

"Stealer" dealers exist everywhere. I have been victimized by them on several occasions and that is why I learned to repair and service chainsaws and other small engine equipment. My own truck (see my avatar Pic) was victimized by a Firestone dealer that I hired to change the oil. Engine was ruined.

 

[ZeroJunk]

Well, I have been doing this a while. I have yet to see it being any fault of the buyer.

 

[drumbum]

This was my whole contention from the beginning, The low idle was set way to high on the saw. The second saw I purchased (exact same model) was also very high on Low idle with the chain spinning very fast with the brake off. I am a person who takes full accountability for my actions and in this case I feel it was not my faught the saw burned up. The dealer not only gave me one Ms391 with the low Idlle set two high but a second one as well. Stihl made their decision not in my favor. That is life. But this was a valuable learning lesson. Hurt my pocket but in the end I have a back up saw for my business and here in Florida storms happen all the time so they come in use one day for that as well.

I'm a bit lost here.....

You posted a vid of the saw at high idle and regular idle.
The chain was not spinning at low idle.

Why do you think the saw was adjusted wrong?

Did you put a tach to it and discovered it was out of factory spec? Or did you just use your calibrated ear from years of experience running and building saws?

I am unaware of a saw that doesn't have the chain spinning at high idle.

It seems all info is disinfo these days.

 

[a. palmer jr.]

User error and he does not want to know what I think.

What I think is to ignore that you even have a chain brake, especially on a plastic saw. Saws did without chain brakes for years now all of a sudden everyone thinks they need one to start the saw, even if it doesn't have a bar and chain on it.

 

[stihltech]

You are assuming the saw is ran by a qualified person before it goes out the door. This is what we were told to do when we started in the 70s. Things have changed.

 

[a. palmer jr.]

If you are lucky it's just the clutch cover melted not the case.

That's one of the reasons I hate plastic clamshells.

Clamshells are fine for occasional users. I have several clamshells sitting in my garage and they're doing fine. Of course I quit cutting wood when I moved about 3 years ago.

 

[a. palmer jr.]

I would not have asked if I didn’t want to know. That being said I don’t really need any smart ass answers.

I think that's why he didn't give any.

 

[StihlsawuserMS361]

"Stealer" dealers exist everywhere. I have been victimized by them on several occasions and that is why I learned to repair and service chainsaws and other small engine equipment. My own truck (see my avatar Pic) was victimized by a Firestone dealer that I hired to change the oil. Engine was ruined.

Agree WD, I hope they made your engine repair right?
Firestone and similar are known as the "fast food of auto repairs". From my gratitude, they kept me pretty busy @ an Oldsmobile Dealership.

Back to topic, I believe Stihl says start w chain brake on, then immediately release. I know that is directed because of safety, but I'm not a fan of W.O.T. on a cold engine so I do set mine.

 

[ZeroJunk]

The first dozen or so pages of a Stihl manual are CYA.
Some days I may start 20 different Stihl saws. The brake may be on and I'm not paying attention.
It jumps out at you.