New Gen KTM Head Studs....stretched?

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4/21/2020 9:56 AM

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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4/21/2020 2:05 PM

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 ...more

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.

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4/21/2020 2:11 PM

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.

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Powerband in every gear !

4/21/2020 2:16 PM

hydraulic lock under the bolts

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4/21/2020 7:45 PM

WEAL wrote:

hydraulic lock under the bolts

What would cause that?

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4/22/2020 6:35 AM

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 ...more

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.

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4/22/2020 1:30 PM

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.

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Race Bike: 2018 KTM 350SXF

Other Bikes: 1985 CR80R, 1990 CR250R, 1998 PW80, Yeti SB130LR.

Sold: 2016 YZ250F, 2012 CRF250R

4/22/2020 4:24 PM

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 ...more

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 nuts ...more

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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