Piston Failure??? Stihl MS362s

[Canyon Angler]

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

Maybe a mix of acetylene and nitromethane?

 

[MrWizard]

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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So, this one in particular was the 2nd rebuild that failed. Our Silver Tech is responsible for the rebuild. I made sure before the carb and muffler went on that it passed leakdown vac and pressure tests.

 

[MrWizard]

Maybe a mix of acetylene and nitromethane?

Is that in MotoMix
The wildest thing is the bottom side of the piston you can see the aluminum has melted and bubbled. I'll post more pics in a few hours

 

[cuinrearview]

To be consistent across the fleet makes me think fuel. What does damage from water in the gas look like?

 

[MrWizard]

To be consistent across the fleet makes me think fuel. What does damage from water in the gas look like?

Initially I was thinking fuel, after learning of their mixing process. However they do have 7 other MS362s and 5 Husqvarna 550XPs running daily. But the picture with the piston still connected to the crank is with only one tank of MotoMix ran through on a fresh rebuild.

 

[Deleted member 135597]

Pull the flywheel and check the key to see if has been ground down. Too much timing advance can cause preignition

 

[CR888]

Test the fuel, not just from the tank but empty the carb and see what' going on. The piston failures all look similar with major damage to the exhaust side & top of piston. It appears the same thing is happening again & again. I think there severe lean seizures. I'd be checking things like cylinder fins aren't caked up preventing cooling, testing fuel etc.

 

[Mauser]

Everything about this story sounds suspicious to me, especially the two stories about one saw running fine for a year and then magically torching, and another doing the same thing within the first tank of fuel!. Wouldn't surprise me a bit if they had some goon on the team who is getting a kick out of seeing how fast he can hog a saw through the wood and burn up a company saw - it ain't his, so the results are how he gets his kicks.

It is beyond belief to me that even a baboon could run a saw long enough to do what I see in those pictures without KNOWING exactly what was happening in his hands.

 

[MrWizard]

More Photo Evidence

Aluminum bubbled on the bottom side of the piston. Metal transfer damage on all sides of the piston.

 

[MrWizard]

Test the fuel, not just from the tank but empty the carb and see what' going on. The piston failures all look similar with major damage to the exhaust side & top of piston. It appears the same thing is happening again & again. I think there severe lean seizures. I'd be checking things like cylinder fins aren't caked up preventing cooling, testing fuel etc.

Fuel in the Carb was the same as in the tank. Fins are clear, brand new cylinder was installed and looks as clean as new. In my experience lean seizures will show a metal transfer on the skirts of the piston, but won't overheat so bad that the piston explodes. Usually seizes before that type of overheating occurs, I feel in this situation that the overheating actually broke down the lubricity of the oil.

 

[CR888]

Yup the underside of the pistons have the dreaded death ash.....not enough oil in mix. Well what do you think is going on?

 

[MrWizard]

Yup the underside of the pistons have the dreaded death ash.....not enough oil in mix. Well what do you think is going on?

the oil would break down at the temperatures these machines would reach, so right track.

 

[pioneerguy600]

Has the muffler screen and exit been checked for obstruction?

 

[dmb2613]

I bet on operator error

 

[MrWizard]

Has the muffler screen and exit been checked for obstruction?

 

[MrWizard]

I bet on operator error

what part of Virginia are you in? I'm in Southwest VA

 

[dmb2613]

I am 25 miles from South Boston, 75 miles from Richmond and 30 miles from Lynchburg , I live in Charlotte County and work at Spaulding Equipment Co, right on the side of hwy 360 18 miles from South Boston

 

[belgian]

Operator error ???


I would like to know what error an operator can make to achieve this result…


Must be a fuel thing for sure if they are non M-tronic.

 

[MrWizard]

I am 25 miles from South Boston, 75 miles from Richmond and 30 miles from Lynchburg , I live in Charlotte County and work at Spaulding Equipment Co, right on the side of hwy 360 18 miles from South Boston

Nice, you're a little over 4 hours away. Ever need anything Stihl or Husky, holler at me.

 

[MrWizard]

Operator error ???


I would like to know what error an operator can make to achieve this result…


Must be a fuel thing for sure if they are non M-tronic.

Only operator errors I know of that could cause this is are covering the vents on the starter cover, really long cuts with a dull chain, or getting it jammed holding it wide open til it fails.