New Gen KTM Head Studs....stretched?

stone881
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866
Joined
12/26/2014
Location
Fruita, CO US
4/21/2020 9:56am
After replacing the top end on my 17 250 SXF, I can't seem to stop coolant from getting into the head. Had the head/jug decked, torqued to 40 lbs, new gasket, and it is still happening.

One guy thought maybe the studs stretched, anyone seen this on their KTM?

Any idea?
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aees
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1505
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8/20/2015
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US
4/21/2020 2:05pm
stone881 wrote:
After replacing the top end on my 17 250 SXF, I can't seem to stop coolant from getting into the head. Had the head/jug decked, torqued...
After replacing the top end on my 17 250 SXF, I can't seem to stop coolant from getting into the head. Had the head/jug decked, torqued to 40 lbs, new gasket, and it is still happening.

One guy thought maybe the studs stretched, anyone seen this on their KTM?

Any idea?
Place it, and cylinder, on a flat surface lika a mirror or piece of glass, or polished ceramic tile to see if you possibly twister it.
FGR01
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AZ US
Fantasy
1334th
4/21/2020 2:11pm
Either one of the surfaces wasn't cut flat, or the studs or nuts are bottoming out before making full contact due to the total height of the cylinder and head now being less.
WEAL
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11/6/2018
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DE
4/21/2020 2:16pm
hydraulic lock under the bolts
stone881
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866
Joined
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Fruita, CO US
4/21/2020 7:45pm
WEAL wrote:
hydraulic lock under the bolts
What would cause that?

The Shop

Matt_B_#57
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4/16/2020
Location
Douglasville, PA US
4/22/2020 6:35am
stone881 wrote:
After replacing the top end on my 17 250 SXF, I can't seem to stop coolant from getting into the head. Had the head/jug decked, torqued...
After replacing the top end on my 17 250 SXF, I can't seem to stop coolant from getting into the head. Had the head/jug decked, torqued to 40 lbs, new gasket, and it is still happening.

One guy thought maybe the studs stretched, anyone seen this on their KTM?

Any idea?
Did you torque the head nut in a cross pattern and step up the torque 3 times per the manual? The order I torqued my head nuts are in this order:
1. Intake Right
2. Exhaust Left
3. Intake Left
4. Exhaust Right

Three torque steps are as follows – be sure to torque in the order listed above for each step:
1. 7.4 lbf*ft
2. 22.1 lbf*ft
3. 36.9 lbf*ft

Also, what head gasket did you go with? I used a Tusk on my 250 with no issues. Used the same type of Tusk gasket on my 350 and had the same issue you are having so I went back to OEM. The OEM gaskets have a nice rubber surface on the metal that creates a better seal in my opinion. The Tusk gaskets are just metal with no rubber so smaller warping issues will become bigger problems. Be sure the head surfaces are clean as well since the OEM rubber will sometimes stick to them and that could create issues as well.
1
c0ncEpT
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Harrison Twp., MI US
4/22/2020 1:30pm
WEAL wrote:
hydraulic lock under the bolts
stone881 wrote:
What would cause that?
Fluid in a blind hole. Typically when this happens with an aluminum block it will actually blow the side of the block out when torqued.
stone881
Posts
866
Joined
12/26/2014
Location
Fruita, CO US
4/22/2020 4:24pm
stone881 wrote:
After replacing the top end on my 17 250 SXF, I can't seem to stop coolant from getting into the head. Had the head/jug decked, torqued...
After replacing the top end on my 17 250 SXF, I can't seem to stop coolant from getting into the head. Had the head/jug decked, torqued to 40 lbs, new gasket, and it is still happening.

One guy thought maybe the studs stretched, anyone seen this on their KTM?

Any idea?
Matt_B_#57 wrote:
Did you torque the head nut in a cross pattern and step up the torque 3 times per the manual? The order I torqued my head...
Did you torque the head nut in a cross pattern and step up the torque 3 times per the manual? The order I torqued my head nuts are in this order:
1. Intake Right
2. Exhaust Left
3. Intake Left
4. Exhaust Right

Three torque steps are as follows – be sure to torque in the order listed above for each step:
1. 7.4 lbf*ft
2. 22.1 lbf*ft
3. 36.9 lbf*ft

Also, what head gasket did you go with? I used a Tusk on my 250 with no issues. Used the same type of Tusk gasket on my 350 and had the same issue you are having so I went back to OEM. The OEM gaskets have a nice rubber surface on the metal that creates a better seal in my opinion. The Tusk gaskets are just metal with no rubber so smaller warping issues will become bigger problems. Be sure the head surfaces are clean as well since the OEM rubber will sometimes stick to them and that could create issues as well.
Yes I stepped it up as mentioned and it actually calls for the 3rd step to be 36.9 degrees past the 22.1 lb, which I did.

Used Vertex gaskets, so don't think that it is the problem. Unfortunately its a 270 so the stock gaskets won't work.

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