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Posted: 8/10/2012 12:31:13 PM EDT
My bike spends it's life digging through sand, climbing mountains, and bouncing off the rev limiter.
The engine is far from stock and has been over-bored to 100mm and the crank and rod stroked to 65mm. It also has a ported and polished head with oversized valves and a stage 2 cam, intake and full exhaust. Normally, it runs like a raped ape, but earlier this year it started running poorly (smoke pouring out of the air box and stalling). After an engine teardown, I now see why. Exhaust gasses were being forced through the piston and into the crank. Another few minutes and the entire motor would have Glocked itself. 
Luckily it only needed a new piston and it's now running great. 
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Posted: 8/10/2012 12:32:26 PM EDT
[#1]
The piston looks in generally good shape otherwise. Did you clean it up a bit before the pictures?
CMS |
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Posted: 8/10/2012 12:39:16 PM EDT
[#2]
Cast or forged piston? If it is cast, I can understand it. Cast pistons are very brittle. Forged is another story. If you put a forged piston you might want to let it warm up before you ride it. Forged pistons are very soft and have a tendency to want to deposit themselves onto the cylinder wall if not warmed up and expanded.
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Posted: 8/10/2012 12:43:26 PM EDT
[#3]
Hypereutectic pistons are a good compromise. I use them often.
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Posted: 8/10/2012 12:43:40 PM EDT
[#4]
Ouch. Glad you got it before it cost you a shit ton.
Nice bike OP, I miss my little YZ125. 
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Posted: 8/10/2012 12:45:52 PM EDT
[#5]
Shit man Ive melted my share of 2 stroke pistons.. that crack is nothing!
cchurchi.. sir you need to IM me your address. I have the 300BLK bullets I promised done..  i even have a few hollow point for ya too.
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Posted: 8/10/2012 12:46:18 PM EDT
[#6]
Cot dam, son.
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Posted: 8/10/2012 12:48:29 PM EDT
[#7]
it is life
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Posted: 8/10/2012 12:50:03 PM EDT
[#8]
Is it a Weisco piston?
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Posted: 8/10/2012 12:50:04 PM EDT
[#9]
Quoted:
Shit man Ive melted my share of 2 stroke pistons.. that crack is nothing! cchurchi.. sir you need to IM me your address. I have the 300BLK bullets I promised done.. i even have a few hollow point for ya too.Ha! Sweet. Maybe I'll see how they work against cracked pistons. |
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Posted: 8/10/2012 1:00:58 PM EDT
[#10]
Quoted: Is it a Weisco Seizico piston?  |
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Posted: 8/10/2012 1:23:26 PM EDT
[#11]
Quoted:
Quoted:
Is it a Weisco Seizico piston?
haha |
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Posted: 8/10/2012 1:32:58 PM EDT
[#12]
Quoted:
Is it a Weisco piston?
seems to be a common theme here..... |
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Posted: 8/10/2012 1:34:21 PM EDT
[#13]
Quoted:
Cast or forged piston? If it is cast, I can understand it. Cast pistons are very brittle. Forged is another story. If you put a forged piston you might want to let it warm up before you ride it. Forged pistons are very soft and have a tendency to want to deposit themselves onto the cylinder wall if not warmed up and expanded. I don't think thats how it works 
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Posted: 8/10/2012 1:37:28 PM EDT
[#14]
Ouch.
When they crack that's where it usually happens. How long for that to happen? |
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Posted: 8/10/2012 4:27:43 PM EDT
[#15]
The piston is a year old. I may have overfilled the crank case.
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Posted: 8/10/2012 4:32:55 PM EDT
[#16]
Done that with forged pistons in the drag car.
It happens, be glad you caught it on time. luckily we've caught it on time twice. 
First time was pretty much the same thing, second was the ring landings. |
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Posted: 8/10/2012 5:37:25 PM EDT
[#17]
A little JB Weld on that (maybe top and bottom) and you should be good to go.
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