Cr 250 2003 - head gaskets

Clint_ezra
Edited Date/Time 4/11/2016 8:59am
Ok so last week I installed a new piston ring in her to keep her sweet...

I took the bike out today!
In the second lap of practice I heard hard detonating, and pulled over!

I lost a lot of compression so walked her back to the pits!

Plug was wet and I had lost coolant!
Took the head off - blown a head gasket!
Now j thought that this was due to not enough torque on the two nuts on the head, nearest the exhaust!


So I put new head gasket on,
And it felt like the cylinder stud nearest the exhaust was stripped of thread a bit (turning with little tension)

But we got some good purchase on it (yes I know, torque wrench next time)

So she starts ok once we got all the coolant out of the bottom end

Went to the line for my moto and I got coolant coming out of my overflow
So I am assuming a head gasket again!

Anybody know common reasons for two blown head gaskets...

a) warped head/cylinder
b) no oil in petrol (although I thought this would seine bearings first)
C) power valve way out of tune!!
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Paw Paw 271
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Paw Paw 271 4/10/2016 5:46pm
4/10/2016 5:46pm
Running an engine without the head tightened to spec is the easiest way to warp the head. After that it will continue to blow head gaskets until it is corrected by milling the head. When you mill the head, the squish will then need to be adjusted as well.

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FGR01
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FGR01 4/11/2016 8:59am
4/11/2016 8:59am
You're going to have to do something about that stripped stud. It might be repairable with a time-sert. Also, when milling the head flat, also mill the top of the cylinder, just enough to ensure flatness. On my 2002 CR250 the top of the cylinder had a taper to it. Sometimes it happens because it is harder near the center where the nikasil is.

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