Grenade!!!!!!!!!!!!!!!!! Warning, GRAPHIC content!!!

[nmurph]

what i noticed is the small dings in the top of the piston. it looks like a circlip came loose, bounced around on the top for several revs and then hung in some of the lower transfers where it detonated the piston.

 

[Tzed250]

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Yeah, the more I look at it the more it appears that the flywheel side of the upper ring pushed into the port. See how the piston is broken in line with the locating pin, and the port floor is broken down and out. My best guess anyway.


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[Fish]

I have seen a lot of toasted pistons, rings break, circlips, bearings etc.

Almost all if not all were oem, never have seen a piston reduced to gravel.

Which makes me still say it was a casting failure..

 

[Deets066]

Sorry for the loss, i know how you feel just when you think your goin to give her a run she takes a s#@t on ya. I put 2 out of 3 pistons in backwards in a snowmobiele once, dropped the rings on both but didn't do near that much damage.

 

[ross_scott]

sorry to see all your hard work on that saw go up in smoke I guess you were lucky it never happened at a GTG.

 

[blsnelling]

Looks to me like it hung a ring on the way down. No matter what that happened, the evidence is the top land blown off. Circlips usually don't cause that much damage.

I'm not following you. There's nothing for the rings to catch on the intake port on the way down. Or are you referring to the transfers? I don't think the transfers are near wide enough to catch a ring. Plus they were beveled after widening.

Possible something was in the exhaust that was sucked in when you blipped it

Definately nothing in the exhaust. It was just assembled.

Yeah, the more I look at it the more it appears that the flywheel side of the upper ring pushed into the port. See how the piston is broken in line with the locating pin, and the port floor is broken down and out. My best guess anyway.

I'm still not following you. The top ring would never have dropped into the port. It would have to be the lower one.

I have seen a lot of toasted pistons, rings break, circlips, bearings etc.

Almost all if not all were oem, never have seen a piston reduced to gravel.

Which makes me still say it was a casting failure..

There had to be an abnormal force that caused it to break. I'm not blaming a casting. I will comment that this piston is made out of something different than anything I've seen before. It is extremely hard and was difficult to cut, even with a carbide burr.

 

[Tzed250]

I'm not following you. There's nothing for the rings to catch on the intake port on the way down. Or are you referring to the transfers? I don't think the transfers are near wide enough to catch a ring. Plus they were beveled after widening.




I'm still not following you. The top ring would never have dropped into the port. It would have to be the lower one.


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Operators left upper transfer. Is that not the side of the piston that has the top broken out?

Why couldn't the ring get in there, it passes all the way over the port on the way down...


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[blsnelling]

Operators left upper transfer. Is that not the side of the piston that has the top broken out?

Why couldn't the ring get in there, it passes all the way over the port on the way down...


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I suppose it could be that would surprise me with it being no wider than it is. Also, I don't think that would puta gouge in the cylinder like it did.

 

[Tzed250]

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That port is pretty durn wide Brad.


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[troutfisher]

Is this the intake port with the Cylinder upside down? Looks like a ring snagged it on the way up.

 

[blsnelling]

Is this the intake port with the Cylinder upside down? Looks like a ring snagged it on the way up.

Yes, it is. I'm convinced the ring caught, but my theory is the the damage was started at the transfer port. IMHO, the ring end looks too far from the edge of the port to have been the initial cause. No?

I appreciate all the opinions and feedback. Don't let my opinions stop you. This is a discussion. I'm not 100% convinced of any theory at this point. Probably no way to ever know for sure.

 

[troutfisher]

Yes, it is. I'm convinced the ring caught, but my theory is the the damage was started at the transfer port. IMHO, the ring end looks too far from the edge of the port to have been the initial cause. No?

I appreciate all the opinions and feedback. Don't let my opinions stop you. This is a discussion. I'm not 100% convinced of any theory at this point. Probably no way to ever know for sure.

Very well could be. Man, that's a lot of damage to sort through and try to figure out what happened first!

 

[blsnelling]

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That port is pretty durn wide Brad.


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So I should make it wider next time

 

[Rounder]

`

 

[Tzed250]

So I should make it wider next time

Install the gapless rings and you are good to go!!!!


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[blsnelling]

I've seen this several times before. That's all I'm going to say. There is a definite reason for what happened here. - Sam

That doesn't help us much

 

[Rounder]

`

 

[blsnelling]

Install the gapless rings and you are good to go!!!!


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I just need Husky pistons in my Stihls, where the ring ends are towards the middle of the port. Then I can make everything as wide as I want

 

[blsnelling]

I wasn't going to say anything more, but I should add that I don't think Brad's port work was the issue. Not saying another word - Sam

Speak your mind. Just do so civilly. We're just discussing possibilities here. Hopefully we can learn from it. At least, hopefully I will!!!!!!!!!

 

[breymeyerfam]

my personal opinion: lower ring dropped in intake at bdc and broke skirt off on its way up. then on its decent the skirt was laying under piston keeping it from traveling back to bdc thus breaking the bottom of the pin boss and then the c-clip came out doing the damage shown in the transfer on its next round before everything got piled up in the bottom. i've never saw a just a c-clip coming out do that kind of damage unless the wristpin catches the transfer port.