Blown out cylinder head, 2015 yz250

Kenman
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Kenman
Edited Date/Time 11/29/2014 1:22am
Anyone ever seen something like this?






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hvaughn88
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hvaughn88 11/10/2014 6:20pm
11/10/2014 6:20pm
Damn! You weren't kiddin! What the hell happened?
Kenman
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Kenman 11/10/2014 6:47pm
11/10/2014 6:47pm Edited Date/Time 11/11/2014 5:05am
Not sure. A buddy of mine was practicing and the bike died and started spewing coolant. This was towards the end of the day. They wiggled the spark plug and the whole head separated. Don't think it was fuel related, but they said it looked like the piston made contact with the head. So maybe something with the crank let go? They're having the bike torn down tomorrow.
hvaughn88
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hvaughn88 11/10/2014 6:52pm
11/10/2014 6:52pm
That's a bummer! Hopefully your buddy wasn't hitting a jump or something like that when it happened
hvaughn88
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hvaughn88 11/10/2014 6:53pm
11/10/2014 6:53pm
Do you have a picture of the piston?

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Harry Backmon 11/10/2014 7:37pm
11/10/2014 7:37pm
I can honestly say I've never seen a grenading quite like that. Any idea how many hours?
reded
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reded 11/10/2014 8:28pm
11/10/2014 8:28pm
Holy pissballs! Please update this thread when you find out more about the cause.
markit
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markit 11/11/2014 12:22am
11/11/2014 12:22am
Wow. Never sean that.
Kenman
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Kenman 11/11/2014 5:04am
11/11/2014 5:04am
20-25 hours on the bike, nothing out of the ordinary with the piston. I'll post any updates when I get them.
seth505
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seth505 11/11/2014 7:50am
11/11/2014 7:50am
Wow, lucky the spark plug didn't end up in his ass haha
hvaughn88
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hvaughn88 11/11/2014 8:10am
11/11/2014 8:10am
seth505 wrote:
Wow, lucky the spark plug didn't end up in his ass haha
haha! imagine explaining that one to the ER.

- "I was just riding along and..."

- "Sure you were, sure you were."
nytsmaC
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nytsmaC 11/11/2014 9:27am
11/11/2014 9:27am


danman
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danman 11/11/2014 9:38am
11/11/2014 9:38am
I've seen it once on a KTM 150, but it was high hours. The crank let go and the piston took out the head. The crank got all goofed up and went through the cases. The tranny and clutch were the only good parts left in that motor.
Markopolo400
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Markopolo400 11/11/2014 2:48pm
11/11/2014 2:48pm
I would bet defect in the casting from the factory, contact your dealer, Yamaha might want that engine back. No way it should do that, and look how the hole in the cylinder side is smaller than the hole on the top of the head, interesting.
Moto Mofo
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Moto Mofo 11/11/2014 3:19pm
11/11/2014 3:19pm
What kind of fuel was he running? Any detonation issues?
smoothies862 11/11/2014 5:37pm
11/11/2014 5:37pm
seth505 wrote:
Wow, lucky the spark plug didn't end up in his ass haha
hvaughn88 wrote:
haha! imagine explaining that one to the ER.

- "I was just riding along and..."

- "Sure you were, sure you were."
"one in a million shot doc"

thats crazy. i would think yamaha would want that on someones desk.
project racer 11/12/2014 12:09am
11/12/2014 12:09am
Markopolo400 wrote:
I would bet defect in the casting from the factory, contact your dealer, Yamaha might want that engine back. No way it should do that, and...
I would bet defect in the casting from the factory, contact your dealer, Yamaha might want that engine back. No way it should do that, and look how the hole in the cylinder side is smaller than the hole on the top of the head, interesting.
Good possibility. Once the combustion chamber portion broke free, and dropped down into the bore a bit, the last few revolutions of the crank / rod / piston probably shoved the broken combustion chamber portion through the top of the head.

slipdog
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slipdog 11/12/2014 6:30am
11/12/2014 6:30am
I'm pretty sure it was Mike Alessi's fault.
CamP
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CamP 11/12/2014 7:12am
11/12/2014 7:12am
LOL slipppy.

My guess is the head gasket blew, filled the combustion chamber with coolant, then hydraulic the head.

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privateerconnection 11/12/2014 11:44am
11/12/2014 11:44am
Was he running pump gas? I am guessing detonation. Current pump gas is murder on all the YZ smokers.
urola
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urola 11/12/2014 3:15pm
11/12/2014 3:15pm
First of all, sorry if I don`t write correctly. I`m from Spain and I'am learning English to go to US on my retirement. You can correct me if you want.

I think this is happened because the seal has been broken, and entered refrigerant in the cylinder. As the coolant can not be compressed the piston has broke whole head easily because it is so hot.
slipdog
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slipdog 11/12/2014 4:32pm
11/12/2014 4:32pm
urola wrote:
First of all, sorry if I don`t write correctly. I`m from Spain and I'am learning English to go to US on my retirement. You can correct...
First of all, sorry if I don`t write correctly. I`m from Spain and I'am learning English to go to US on my retirement. You can correct me if you want.

I think this is happened because the seal has been broken, and entered refrigerant in the cylinder. As the coolant can not be compressed the piston has broke whole head easily because it is so hot.
You did fine for a second language and I believe your idea is logical. Just like CamP said two posts above yours, here you'd say

" the head gasket blew and filled the cylinder with coolant causing the head to fracture from the hydraulic pressure."
urola
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urola 11/13/2014 1:44am
11/13/2014 1:44am
Thanks ;-)
Markopolo400
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Markopolo400 11/14/2014 6:47am
11/14/2014 6:47am
Any more pictures?
Falcon
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Falcon 11/14/2014 2:10pm
11/14/2014 2:10pm
Markopolo400 wrote:
I would bet defect in the casting from the factory, contact your dealer, Yamaha might want that engine back. No way it should do that, and...
I would bet defect in the casting from the factory, contact your dealer, Yamaha might want that engine back. No way it should do that, and look how the hole in the cylinder side is smaller than the hole on the top of the head, interesting.
That has to be from the dome shape of the combustion chamber. The weakest parts would be around the base of the dome, not on the curved dome itself. When that part let go, the dome passed through the water jacket area, slammed into the top portion of the cylinder head, and broke that at its weakest point as well.

I concur about the hydraulic pressure.
BobPA
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BobPA 11/14/2014 3:30pm
11/14/2014 3:30pm
CamP wrote:
LOL slipppy.

My guess is the head gasket blew, filled the combustion chamber with coolant, then hydraulic the head.
Yes
Rdubs19
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Rdubs19 11/17/2014 1:07pm
11/17/2014 1:07pm
Any update on this??
YamaLink
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YamaLink 11/20/2014 3:39pm
11/20/2014 3:39pm
Did a double take on that first pic!
Kenman
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Kenman 11/20/2014 4:57pm
11/20/2014 4:57pm
Still waiting to hear back from the owner. I am thinking it may have been hydraulic pressure from a blown head gasket like everyone is mentioning. However, do you think the amount of coolant that could enter the cylinder head be greater than the amount that could be pushed out of the exhaust port?
theonlinelegend 11/21/2014 5:47pm
11/21/2014 5:47pm
seth505 wrote:
Wow, lucky the spark plug didn't end up in his ass haha
That thing looks like it was close to being a story line on that show 1000 ways to die. I'm still trying to wrap my head around that head flaring out like that at the sparkplug. Unless my eyes are deceiving me. OP, what did the dealership have to say?
smezmx
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smezmx 11/29/2014 1:22am
11/29/2014 1:22am
Any update's? Interested to see it.

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