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Discussion Starter · #1 ·
Gi guys after a wee bit advice had my sx 125 sitting a while now bike had a heat seizure and wrecked the barrel , so it sat a while got the barrel redone at langcourt , rebuilt it with full new top end piston gaskets etc , fired up and it starts to leak via the overflow grrrrr, so peace of mind more new gaskets new head bolts new coolant try again , nope still leaking took rad cap off and it's foaming and bubbling like its got rabies,

so the gaskets are all good the barrels fresh all bolts torqued to spec .

So does this mean ive warped the head ?
If i have is it better to replace or have it machined ?

Its a 2007 125 with a vhm head and insert
Thanks in advance guy's :)
 

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It easy enough to see if the head is warped, just use a steel ruler across the face of the head and hold it up to a light source to see if any light is showing between the head and the edge of the ruler.
If the head is warped it could probably be fixed. What caused the first seizure?...I'm wondering whether you have a water pump issue and you still have that issue.
 
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Discussion Starter · #3 ·
Sorry should have said also had full water pump rebuild all oem parts,

As for the first seizure lt was definitely heat seizure due to the damage its happened on the track id foolishly not checked my water pre ride once off the track and parked up back home i noticed a leak from the front of the head so must have had a unnoticed leak to start.

I should note the frothing and overflow is immediately upon starting indicating back pressure in the system 🤔
 

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Don't just assume anything without checking it first...you could end up chasing your tail and it costing you money.

You might have a warped head, could be something trapped between barrel and head, could be dirt/debris in the oring grooves in the barrel, what make were the gaskets/o rings etc, did you grease the orings when you fitted them, were there any burrs on the head/barrel? etc etc

There's lots of things it could be.... so don't just assume the head is warped....
 

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Discussion Starter · #5 ·
All gaskets and o rings head bolts the lot were oem ,
Barrel just refurubed so spotless
As for the head and insert no obvious damage or marks very slight pitting underside of the insert so i smoothed out with wet an dry
 

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Is the insert o ring ok? VHM recommend renewing it every 4th time you've had it apart from the head.
 

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Discussion Starter · #7 ·
Is the insert o ring ok? VHM recommend renewing it every 4th time you've had it apart from the head.
That is a good shout its in fine visable condition, however I've never changed it ,
so I'll give that a try cheers
 

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Check that VHM doesn’t specify a different diameter oring to. The ktm oring could be smaller and not sealing as well? Just a thought.
 

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We used VHM heads on our 125s for years, and while never say never, I would be surprised if the head would warp. Anyway, did you use KTM gaskets or aftermarket? I don't know how many 125 pistons I've changed since 2007, is loads every 15 hours in 2 bikes and only issue we ever had was (once, in a rush) using aftermarket head rings which leaked and destroyed a new piston. Bob
 

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Discussion Starter · #10 ·
We used VHM heads on our 125s for years, and while never say never, I would be surprised if the head would warp. Anyway, did you use KTM gaskets or aftermarket? I don't know how many 125 pistons I've changed since 2007, is loads every 15 hours in 2 bikes and only issue we ever had was (once, in a rush) using aftermarket head rings which leaked and destroyed a new piston. Bob
Hi all gaskets o-rings bolts etc were oem
I try to allways use genuine ktm parts
 
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