Ms200 - kaboom!!

[komatsuvarna]

Id clean that piston up and run it,,, and not think twice about it! You do need to find out where the chunks came from. All the screws still in the carb butterflys? Can you see the crank and rod bearings? Had someone else recently been into it?

 

[lone wolf]

check the crank bearing cages for missing parts.:msp_thumbup:

Rod bearing

 

[brokenbudget]

Rod bearing

i've seen both, but looking at the picture it doesn't look like any parts from a bearing. could be that they were just chewed up beyond recognition.
how about a pic of the transfers in the cylinder? could this be from casting flash? just throwing that out there. still think it was a bearing deciding it didn't want to do the job anymore:hmm3grin2orange: maybe some of the case let go? hmmmmm.:smile2:

 

[gcsupraman]

i've seen both, but looking at the picture it doesn't look like any parts from a bearing. could be that they were just chewed up beyond recognition.
how about a pic of the transfers in the cylinder? could this be from casting flash? just throwing that out there. still think it was a bearing deciding it didn't want to do the job anymore:hmm3grin2orange: maybe some of the case let go? hmmmmm.:smile2:

It's not the main rod bearing as I can slide the connecting rod over and spin the crank. All the bearings are perfect on it....

Looks like the piston was peppered underneath as well. Going to pull the piston pin out....standbye

 

[Opihi59]

You did say the pieces you retrieved were Aluminum. If they are non ferrous, a magnet won't attract them, and they would have to be steel if they were bearing spall. Very hard to figure from where they came, especially since the aluminum components you have shown do not appear to have tell-tale chunks missing. If there were to be no screen inside your muffler, that could allow something to get in thru the exhaust port, or if there are some pieces that got sucked thru your carb or somehow broke off from inside it, those could get into the combustion chamber thru the transfers. Air filter would generally protect from something external going walkabout in your saw. I'm not an expert either, this is a puzzle and I'm interested in hearing what you find out.

 

[lone wolf]

Aint that much it could be really left or rt main bearing ,lower rod bear is all that is left.I wonder if it is a chunk of the muffler?

 

[gcsupraman]

You did say the pieces you retrieved were Aluminum. If they are non ferrous, a magnet won't attract them, and they would have to be steel if they were bearing spall. Very hard to figure from where they came, especially since the aluminum components you have shown do not appear to have tell-tale chunks missing. If there were to be no screen inside your muffler, that could allow something to get in thru the exhaust port, or if there are some pieces that got sucked thru your carb or somehow broke off from inside it, those could get into the combustion chamber thru the transfers. Air filter would generally protect from something external going walkabout in your saw. I'm not an expert either, this is a puzzle and I'm interested in hearing what you find out.

Just grabbed a magnet....there were about 5 or 6 chunks all of them not attracted to the magnet heart: = no)

Took the piston out....hard to tell by the photos but it was defiantly blasted from underneath at some point but no real damage. Same in the crankcase - little peppered metal marks but nothing obvious.

Lonewolf - This one is a mystery to both of us. I could pull the case apart - I assume it's just remove all the screws I can find and it comes apart. But if there is nothing in the lower end that is aluminum it's not worth it. And everything rotates perfectly.

 

[lone wolf]

How about the circlip on the inside of the air filter cover? or a piece of the muffler look at the muffler after you pull it.Dont split the cases yet.Must be the muffler if its not magnetic!

 

[rmh3481]

I think you will find its part of a bearing. If you need the manual, send me an email address via a private message and I will forward you a pdf copy.

 

[brokenbudget]

I think you will find its part of a bearing. If you need the manual, send me an email address via a private message and I will forward you a pdf copy.

anything from the bearing is going to be magnetic. he's already tried the bits an one:frown: i think his husky buddies tried to sabotage the poor little stihl:hmm3grin2orange:

 

[little possum]

Id take a peek in the muffler. Sometimes things go amiss in there, I had a large piece outta a 394 muffler that was just rattling around, sounded like the crank was banging at first

 

[lone wolf]

I think you will find its part of a bearing. If you need the manual, send me an email address via a private message and I will forward you a pdf copy.

PDF in my sig

 

[gcsupraman]

anything from the bearing is going to be magnetic. he's already tried the bits an one:frown: i think his husky buddies tried to sabotage the poor little stihl:hmm3grin2orange:

They wouldn't be buddies if they owned Huskys

Took the muffler apart, nothing missing from there. Nothing missing from the intake or carb.

There really isn't much it could be because it's not magnetic - looks like Stihl left a few extra pieces in there for me I guess.

-Greg

 

[lone wolf]

Got any enemies?

 

[CWME]

View attachment 207843


Can't really tell in the photo but is there something missing where I circled in red?

 

[lone wolf]

Cant tell either to blurry.

 

[bama]

View attachment 207843


Can't really tell in the photo but is there something missing where I circled in red?

If it is, then I am wondering what caused it and will more of it come off?? Been lucky so far. It HAS to be from the piston since it is aluminum, so somewhere there is a little chunk missing.

 

[blsnelling]

Perhaps this isn't the original piston. Maybe these are pieces from a previous failure and they just now got sucked out of the bottom end and into the combustion chamber. I think you've pretty much covered your bases. Put it back together and run it.

 

[gcsupraman]

If it is, then I am wondering what caused it and will more of it come off?? Been lucky so far. It HAS to be from the piston since it is aluminum, so somewhere there is a little chunk missing.

I took the piston out and inspected it for probably 30 minutes with a flashlight - nothing. This is unbelievable.

The aluminum is the killer as there aren't many options. I'm stumped - they sure don't teach you these things in high school power tech class

New piston rings are on order. I cleaned everything out with a compressor and should have it back together this week (along along with an 012av i'm rebuilding - same piston rings I found out today believe it or not).

If it happens again it should be more obvious where these metal pieces are coming from

-Greg
PS Here is a different angle of the piston - the first picture looks like it was a possibility but this should clear it up. My wife has this super expensive camera that I can't figure out how to use so the pics aren't the greatest - sorry.

 

[sdmaker]

Perhaps this isn't the original piston.

This is my guess as well. someone blew it up at some point and didnt get all the old piston out of the bottom end.