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Top piston blow-up


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Brollocks

 
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Top piston blow-up

Mon Oct 10, 2005 8:18 pm » Post: #1 » Download Post

Hey Guys

My top piston blew on my last race meeting. When i got home home after a miserable day, i decided to have a look and see how the piston looks. First i had a look at my bottom piston and found that it was looking as good as new. Next i went on to have a look at my top piston.... What i found was a piston and the head full of pen-point size holes around the radius of both, but my barrel didn't have a single scratch on them and the piston ring was still in tach.
I knew my gasket was blowing in the race as the overflow bottle was full of water, but the temp was still at 70 just before it popped.

Could it be that water got in the head and made so much damage? Secondly, how important is it to use a torque wrench when putting on the heads(Can over tightning cause the gasket to blow????)

Thx a thousand!
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Dave Ett
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Tue Oct 11, 2005 4:27 am » Post: #2 » Download Post

I think that damage is detonation, caused by pre-ignition , caused by the cylinder getting too hot, caused by the lack of cooling around the head!

It is absolutely crucial to use a torque wrench. Over tightening can cause the head to warp - it's only soft alloy!

You were damn lucky by the sounds of it, so buy a new piston and a new tool to rebuild it with! Wink
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Brollocks

 
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Tue Oct 11, 2005 8:38 pm » Post: #3 » Download Post

Thx

Will check the heads and barrels out to see if they are still completely flat and then rebuild the bike using a torque wrench.
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Binka

 
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Re: Top piston blow-up

Wed Oct 12, 2005 7:30 pm » Post: #4 » Download Post

Brollocks wrote:Hey Guys

My top piston blew on my last race meeting. When i got home home after a miserable day, i decided to have a look and see how the piston looks. First i had a look at my bottom piston and found that it was looking as good as new. Next i went on to have a look at my top piston.... What i found was a piston and the head full of pen-point size holes around the radius of both, but my barrel didn't have a single scratch on them and the piston ring was still in tach.
I knew my gasket was blowing in the race as the overflow bottle was full of water, but the temp was still at 70 just before it popped.

Could it be that water got in the head and made so much damage? Secondly, how important is it to use a torque wrench when putting on the heads(Can over tightning cause the gasket to blow????)

Thx a thousand!


What did the plug look like ?
The aftermath of a gasket letting go can resemble pre-ig...

bad luck
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