What caused this! Piston Pics

[grandpatractor]

Was the piston hittinh the top of the combustion chamber? It looked from the picture it was. Was the OEM base gasket installed and was the piston slapped out so bad it was rocking?
I wish I was there!

It wasn't hitting the top. It was eroded away from the detonation. Both the piston and the top of the cylinder.

 

[Jacob J.]

How the hell did you know that?

I've been inside a few of them.

Once you work on enough engines from a certain manufacturer, you start to recognize certain design characteristics.

It's like how my Grandpa could always tell a Cat motor from a Cummins or a Detroit Diesel just by the sound of it.

 

[Jacob J.]

It wasn't hitting the top. It was eroded away from the detonation. Both the piston and the top of the cylinder.

Yeah the dimpling is where the material in both the piston and the cylinder actually got hot enough to go molten.

If this had been just a head-smacker, then the surfaces would be flat and well-defined.

 

[Urbicide]

How the hell did you know that?

Jacob was gifted with special powers. opcorn:

 

[Teddy.Scout]

Yeah the dimpling is where the material in both the piston and the cylinder actually got hot enough to go molten.

If this had been just a head-smacker, then the surfaces would be flat and well-defined.

Bad top end?
What would be the reason for this. (getting to hot.)
By my NOVICE eye, if it was a small to good air leak, wouldn't the scoring be more aggressive?

 

[Jacob J.]

Bad top end?
What would be the reason for this. (getting to hot.)
By my NOVICE eye, if it was a small to good air leak, wouldn't the scoring be more aggressive?

Running low quality or stale fuel.

 

[jra1100]

Knowing Grampatractor I'd just chalk it up to bad Karma.

Grampa, I hope that your not freezing up there in Sconi land. Have a Merry Christmas. JR

 

[Teddy.Scout]

I am learning here,
How long would it take running a saw with poor fuel to cause this?
Immediate or after a couple tanks??

 

[promac850]

I am learning here,
How long would it take running a saw with poor fuel to cause this?
Immediate or after a couple tanks??

Couple of tanks can be all it takes. If it's really bad fuel, just a little too long (couple of minutes) of run time can be enough to destroy the piston.

If you hear pinging (detonation) turn the saw off and get better fuel in it. Don't cut for too long on it. If you need to finish a felling cut to safely drop a tree then do so. I would not go on to limbing until fresh mix was poured in.

Now, if you had say, a third or quarter of a tank of stale fuel, adding fresh on top and mixing would probably be fine and should not result in detonation.

If it's a full tank, dump it into an empty gas can and pour it into the gas tank on your truck. Don't run that stale crap in any saw, unless it's one that you hate and can't give away to someone for whatever reason...

Stale fuel is such that is has been sitting for a real long time and has lost most to all of its original octane value. Obviously, that isn't a good thing and leads to problems, grandpatractor's p/c in this thread is an example.

 

[brokenbudget]

hey look a poor mans pop up:hmm3grin2orange: just mill some of the bottom of the cylinder to match the material that was blasted off the piston and you good to go!