Piston Failure??? Stihl MS362s

[kenton.a.frank]

One would think he could have dumped motomix in after failure. I’ve only seen this with poor quality fuel or water in fuel.


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[HarleyT]

I think the customer is not telling you something very important on these failures...

 

[kenton.a.frank]

I’ve had these failures on 361s and 362s both of which the customer stares it is the saw they abuse the most. Running 25in bar close to the ground stumping. Additionally they admitted with wet season it could have gotten water in the fuel.

Not to be a Stihl fan boy over here but these saws cut really well and they may be pushing them harder than they should in many ways.


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[MrWizard]

These are not usual failures, and for these to be from the same customers, well, kind of a big clue!!
So, throwing out details to blow our minds, well, without any more details, kind of silly.

What other details would you like? I would gladly give them. Just thought I listed plenty. Let's start from the beginning, we'll use one saw for example. They bought it new, run it for a year, it blows a hole in the piston one day, we rebuild it top and bottom end, passes all post rebuild tests, send it with the customer, with only Stihl Moto Mix, it fails again in one tank full by blowing yet another hole in the piston.

 

[HarleyT]

Are the other saws used by the same crew? Same guy? What kind of work?
A full rebuild, and no going through the carb?
What was the original cause of failure?

 

[kenton.a.frank]

Are the other saws used by the same crew? Same guy? What kind of work?
A full rebuild, and no going through the carb?
What was the original cause of failure?

If it blew in one tank... I’d suspect something was missed in the rebuild or the customer did something to it.

If rebuilt again I’d run a few tanks through it before sending it out the door.


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[HarleyT]

The pistons shown look more like straight gas. Can you show the other side of the pistons?

 

[dmb2613]

We had a guy burn up 2 661s in one day, come to find out he was cutting bails of wet tobacco with them and having the muffler tight up against the wet bail , just flat overheated them. Check out the users something is bad wrong

 

[MrWizard]

Let's use one saw for example. They bought it new, used it for 1 year, one day it blows a hole threw the piston, we rebuild it, passes all post rebuild tests, give customer saw with MotoMix, saw blows hole in piston within one thankful of Moto Mix.

 

[MrWizard]

Your rebuild as well?

No, saw came in this way

 

[MrWizard]

I

The pistons shown look more like straight gas. Can you show the other side of the pistons?

I'll post more pics from the bench tomorrow.

 

[MrWizard]

So then, they are using crap fuel, or something very close.

87 Octane from a local supplier not a gas station. Supposedly 100%. My recommendation for these Pro Saws is 93

 

[MrWizard]

We had a guy burn up 2 661s in one day, come to find out he was cutting bails of wet tobacco with them and having the muffler tight up against the wet bail , just flat overheated them. Check out the users something is bad wrong

That sounds like a really bad day, did the failure look like this?

 

[Big Red Oaks 4 me]

Are they all M-tronic saws? If so, I'd assume it's one of those faulty modules that a local Stihl guy has been telling me about. I took my 362 to him for the same reason, and didn't bring it back home.

 

[MrWizard]

Are they all M-tronic saws? If so, I'd assume it's one of those faulty modules that a local Stihl guy has been telling me about. I took my 362 to him for the same reason, and didn't bring it back home.

These are Non-MTronic Saws

 

[Big Red Oaks 4 me]

These are Non-MTronic Saws

Well, in that case, I have to agree with the others. Operator-induced failure.

 

[dmb2613]

That sounds like a really bad day, did the failure look like this?

Yes but not nearly as bad. An idiot was running the saw to run it that long without knowing something was wrong.

 

[MrWizard]

Yes but not nearly as bad. An idiot was running the saw to run it that long without knowing something was wrong.

That's was a question I asked, seeing the melted plastic. How could they not have known that something was wrong? Thing had to be hot in the users hands

 

[MrWizard]

One would think he could have dumped motomix in after failure. I’ve only seen this with poor quality fuel or water in fuel.


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This is a pretty professional group of guys at least the ones I get to deal with. It's their reputations and jobs on the line as well. So I don't think foul play is at hand. Least I hope not

 

[MrWizard]

I’ve had these failures on 361s and 362s both of which the customer stares it is the saw they abuse the most. Running 25in bar close to the ground stumping. Additionally they admitted with wet season it could have gotten water in the fuel.

Not to be a Stihl fan boy over here but these saws cut really well and they may be pushing them harder than they should in many ways.


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What did you determine the cause was?