066.....What happened?

[Wagnerwerks]

Disregard this post

 

[Adirondackstihl]

Plenty of oil

 

[Adirondackstihl]

Was it snowing or raining when you were cutting? Any possibility there was moisture in your fuel? Usually scoring on the intake side only is from something washing the oil/lube off the intake side...also known as water score. Condensation forming in the carb maybe from cold temps? Or debris ingestion but like you said...debris probably wouldn't cause the transfer. Something had to of washed that cylinder. My .02.

It was -6 degrees

 

[cutforfun]

Piston heated up and expanded faster than the cylinder?

 

[old-cat]

Very small burr, bottom edge of intake port?

 

[Adirondackstihl]

Very small burr, bottom edge of intake port?

I'll have to check, but I don't think so.
I've already began cleaning the cylinder so there is a chance that if there was a burr, it's gone now

 

[old-cat]

I'll have to check, but I don't think so.
I've already began cleaning the cylinder so there is a chance that if there was a burr, it's gone now

Your piston scars match the bottom of the intake port. I have run coarse sandpaper on the floor of the intake and made a burr that I didn't realize and it made marks on the piston like yours.

 

[Adirondackstihl]

Your piston scars match the bottom of the intake port. I have run coarse sandpaper on the floor of the intake and made a burr that I didn't realize and it made marks on the piston like yours.

I see what youre saying.
This saw had never been apart prior to last night.

 

[HuskStihl]

As knobby said, leaky decomps have killed many saws, but if it was comfortably and clearly 4 stroking out of the cut, and cleaning up with pressure, then the tune should have been fine regardless of leak. All the damage on the intake side speaks to friction rather than heat as the root cause.

 

[Duke Thieroff]

Hey dummy did you vac/pressure test the saw?

Or did you just post on AS about it?


I would've hoped you were smarter than that.

 

[Adirondackstihl]

Hey dummy did you vac/pressure test the saw?

Or did you just post on AS about it?


I would've hoped you were smarter than that.

Why the phuck would I do that?

 

[Homelite410]

Derk a der...... Lol

 

[Duke Thieroff]

Why the phuck would I do that?

Usually when a guy scores a piston he diagnoses the issue.

Maybe it was an air leak, filtration issue, burrs on the port, busted up bearing cage, bad fuel....

Or maybe the aftermarket parts gremlins flew in from the Far East the last time you ran it and threw a fine mixture of aluminum melting/scoring dust directly into the intake pipe of your saw and damaged that beautiful OEM piston beyond repair.

 

[HuskStihl]

Leaks don't kill saws. Not checking u'r tune and letting it go lean kills saws

 

[old-cat]

The marks on that piston don't show signs of heat which is what causes aluminum transfer.

 

[pioneerguy600]

Meausure the bore on both cross axis. I have one here that is badly out of round, so much so that the intake side is .005 narrower than the transfer side of the cylinder.

 

[old-cat]

Meausure the bore on both cross axis. I have one here that is badly out of round, so much so that the intake side is .005 narrower than the transfer side of the cylinder.

That's the way most pistons are manufactured.

 

[Adirondackstihl]

FWIW......I'm not a noob at tuning a saw. Far from it actually.
Nor did the saw act like it had an air leak.....AT ALL.
Ran and idled perfect. Plenty of snort too.
Clean HD air filter.
I'm just baffled.

I would have never found this problem had I not decided to pull the muffler to open up the 2nd port a bit more.

 

[Adirondackstihl]

Leaks don't kill saws. Not checking u'r tune and letting it go lean kills saws

It was 4 stroking so hard outta the cut I thought it was 6 stroking

+ "I have a potty mouth"

 

[Plan-b]

I am going to say this one was a cold seize. If most of the scuffing occurred where the piston has the most mass such as the webbing, points in the cold seize direction.