17 Tc 125 cracked head

final touch
Edited Date/Time 8/11/2019 6:04am
Purchased this bike Friday evening with around 50 hrs on it started up right away with no issues I did notice the coolant was a little low toped it up and thought nothing of it

Rode the bike at my local track Saturday for the first time and all was good until the second session I pulled in and noticed coolant on the ground it was coming from one of the coolant pipes where a jubilee clip had failed ,put a new one on and toped it up with coolant ,started it up and then coolant was pouring out the overflow pipe like the whole system was pressurised.

Got the bike home took the head of and saw this crack in the insert ,my question is what would of caused this ?did it over heat or is there other issues ?i don’t want to replace this part and the same thing happen again any help will be much appreciated.
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final touch 7/14/2019 11:20am
7/14/2019 11:20am
CarlinoJoeVideo wrote:
Do you have a photo of the plug and piston?
I’ll get a picture up soon ,the plug was maybe slightly lean but still brown the threads were black ,haven’t looked at the piston yet but the barrel looked in good condition no scoring and top of the piston looked clean little bit of carbon
Bruce372
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Bruce372 7/14/2019 11:25am
7/14/2019 11:25am
That's crazy, never seen anything like that

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Paul_Pitzonka
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Paul_Pitzonka 7/14/2019 12:17pm
7/14/2019 12:17pm
I’ve seen it before in heads that were machined too thin in the combustion chamber or very high compression applications... as mentioned above I’d believe to be probably be a production defect...
final touch 7/14/2019 12:33pm
7/14/2019 12:33pm
Paul_Pitzonka wrote:
I’ve seen it before in heads that were machined too thin in the combustion chamber or very high compression applications... as mentioned above I’d believe to...
I’ve seen it before in heads that were machined too thin in the combustion chamber or very high compression applications... as mentioned above I’d believe to be probably be a production defect...
The part is only £27 to replace from the dealers do you think this will fix the pressurising problems with the cooling system ?
final touch 7/14/2019 12:37pm
7/14/2019 12:37pm
Just noticed on the parts list they have an updated part for this maybe the old part wasn’t machined to spec
Paul_Pitzonka
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Paul_Pitzonka 7/14/2019 12:45pm
7/14/2019 12:45pm
Paul_Pitzonka wrote:
I’ve seen it before in heads that were machined too thin in the combustion chamber or very high compression applications... as mentioned above I’d believe to...
I’ve seen it before in heads that were machined too thin in the combustion chamber or very high compression applications... as mentioned above I’d believe to be probably be a production defect...
final touch wrote:
The part is only £27 to replace from the dealers do you think this will fix the pressurising problems with the cooling system ?
Definitely will fix your pressurized cooling system issue... and if they list an updated part there was more than likely some sort of flaw or update the company felt was necessary... if everything else looks ok my money is on part defect...
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final touch 7/14/2019 2:09pm
7/14/2019 2:09pm
Paul_Pitzonka wrote:
I’ve seen it before in heads that were machined too thin in the combustion chamber or very high compression applications... as mentioned above I’d believe to...
I’ve seen it before in heads that were machined too thin in the combustion chamber or very high compression applications... as mentioned above I’d believe to be probably be a production defect...
final touch wrote:
The part is only £27 to replace from the dealers do you think this will fix the pressurising problems with the cooling system ?
Paul_Pitzonka wrote:
Definitely will fix your pressurized cooling system issue... and if they list an updated part there was more than likely some sort of flaw or update...
Definitely will fix your pressurized cooling system issue... and if they list an updated part there was more than likely some sort of flaw or update the company felt was necessary... if everything else looks ok my money is on part defect...

Paul_Pitzonka
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Paul_Pitzonka 7/14/2019 8:08pm
7/14/2019 8:08pm
How many hours are on that piston? Everything looks pretty good as far as I can see... I’d replace the head insert as I still think it was more than likely part failure... if the piston has over 40 hrs on it replace that too... if it’s a fairly fresh piston re-ring it, de-glaze the cylinder and you should be good to go
final touch 7/14/2019 11:16pm
7/14/2019 11:16pm
There’s 5 hours on this piston according to the previous owner which I can believe looking at it I’ll get the insert ordered and post back when it’s back together thanks for your help 👍
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riv187
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riv187 7/22/2019 1:00pm
7/22/2019 1:00pm

I have my 2018 head with 7 hrs. $40 USD plus shipping,,,,or do as I did,,and get RK make you one like this. Run smoother with wider power band.
HighPlainsSquid 7/23/2019 6:18am
7/23/2019 6:18am
riv187 wrote:
[img]https://p.vitalmx.com/photos/forums/2019/07/22/361878/s1200_57075044326_07B90438_A2AB_4207_A433_F58152860B9C.jpg[/img] I have my 2018 head with 7 hrs. $40 USD plus shipping,,,,or do as I did,,and get RK make you one like this. Run smoother...

I have my 2018 head with 7 hrs. $40 USD plus shipping,,,,or do as I did,,and get RK make you one like this. Run smoother with wider power band.
I have an RK Tech head insert on my KTM 150 and it transformed the bike. If I were replacing the head anyway, I'd 100% go with RK.

Pit Row

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final touch 8/11/2019 5:59am
8/11/2019 5:59am
Bike all out back together and runs spot on now no overheating and no loss of coolant runs great ,took the head of and a few other pieces today for cerakoting and noticed these faint score marks on the cylinder and power valve you can’t feel them and I’m sure if I used scotch brite they would go ,but what could be causing this ?I’m running 40:1 motorex oil and always run clean filters totally stumped by this

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