The clip is deformed. Did you notice the transfer bridge pushed in a cracked? Something definately got caught in there, whether that's what started it or not.
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- Thread starter blsnelling
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The clip is deformed. Did you notice the transfer bridge pushed in a cracked? Something definately got caught in there, whether that's what started it or not.
WildnCrazyGuy
ArboristSite Operative
Peckerhead will be along shortly and give you the low down. He'll try to get all philosophical and talk about mixed gas, proper ratios, and the like. I'll just go with when you put the piston in you tapped the connecting rod with a hammer and bent it when putting it in.
wigglesworth
Booned
Yea, saw that. That's what got me thinking circlip.
Birdhunter1
ArboristSite Operative
A company called Alliant makes this gunpowder called Green Dot that is fast burning and tends to go KABOOM when you have an excessive oversharge of it..... looks like somebody might have replaced your gasoline with Green Dot.
On second thought maybe something just broke.
On second thought maybe something just broke.
I wonder if you might of had a little piston slap and with the widened porting it caught a port with the piston skirt and them wam broke it. I base this on how the pin boss broke like it did. Its either that or the pin boss is what failed.
I have a theory.
The cirlcip came out. As the piston was moving down, it got caught between the piston and transfer bridge, pushing it out and cracking it. At the same time the ring broke, and was pulled around some what. This allowed the ring end to drop into the intake port. As the piston moved back up, the lower ring caught on the top of the intake port, and broke the entire skirt off.
I might be wrong, but this is the only way I can explain everything I see. The only other scenario would have been for the lower ring to have dropped into the port on it's own, but I don't believe the port to be wide enough for that to happen.
The cirlcip came out. As the piston was moving down, it got caught between the piston and transfer bridge, pushing it out and cracking it. At the same time the ring broke, and was pulled around some what. This allowed the ring end to drop into the intake port. As the piston moved back up, the lower ring caught on the top of the intake port, and broke the entire skirt off.
I might be wrong, but this is the only way I can explain everything I see. The only other scenario would have been for the lower ring to have dropped into the port on it's own, but I don't believe the port to be wide enough for that to happen.
No damage at all to the bottom of the intake port. The pin boss couldn't fail with abnormal force being exerted from some where else.
2000ssm6
Stihl User
That will polish out....
:jawdrop:A new 440.......:jawdrop:
:jawdrop:A new 440.......:jawdrop:
jnl502
ArboristSite Operative
i think a ring hung on that wide intake port. that port is huge from the pictures. that is what i think. that sure was some nice port work Brad sorry for the loss
jnl
jnl
:jawdrop:A new 440.......:jawdrop:
I was FAR more worried about the saw than I was the topend!!!
That is a possibility I'm considering. I've lined everything up as carefully as possible, and don't believe that to be the case. I won't say it wasn't, but I don't think it was. Also, notice how far from the edge of the port that the marks from the ring are. Also, that also would not explain the damage to the transfer bridge, and the fact that it happened on the way down, and the skirt happened on the way up. The physical evidence verifies which direction the piston was moving when the two places were damaged.
Fish
Tree Freak
What brand aftermarket piston was it??
Looks like poor casting.
Looks like poor casting.
wigglesworth
Booned
That makes sense. It did pull a big section off the top of the piston.
MS460WOODCHUCK
Addicted to ArboristSite
The piece missing from the top of the piston happened as the piston moved down. The skirt broke off as it moved back up.
+1 Looks like the ring caught the intake port
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That looks like a possibliity as most of the piston damage is aft (intake side)of the wrist pin on the side that the clip is missing in the pics. I was pondering this as you posted. With so much damage it's hard to tell which came first the chicken or the egg!! Hard to tell if the clip came off by itself or was released by damage. Is the clip in the pic the one that's missing?? If it is, it doesn't seem to show any damage from being squished between the bridge and the piston??
Tzed250
Addicted to ArboristSite
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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.
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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.
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2000ssm6
Stihl User
No doubt. Those pics make me stay farther away from the aftermarket stuff. That kind of failure can happen to either but that sure looks like the piston came apart. Bad thing was it wasn't even WOT.
Possible something was in the exhaust that was sucked in when you blipped it, causing the the t-port and piston top damage from there that created an imbalance and piston slapped and grenaded. At least that's what i can come up with it's the only way I can explain the damage to the t-port and piston top
