Hi-Comp Thin Head Gasket

TVann

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So, I've experienced the dreaded over-heating on my 17 rc390. Overheated, won't run etc. Turns out there's a hole in the radiator from road debris. Brought it to trusted mechanic and had him replace the fan (SPAL), hoses, new radiator. In doing so it appears the head gasket is blown as well.

Given the head gasket needs replacing, I'm intending to do so with the thinner head gasket offered by KTM Performance - bumps up compression. Why not, right?

What, if anything, is the downside?

Thanks for the input. Great site, good people. Cheers.
 

Icehax

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So, I've experienced the dreaded over-heating on my 17 rc390. Overheated, won't run etc. Turns out there's a hole in the radiator from road debris. Brought it to trusted mechanic and had him replace the fan (SPAL), hoses, new radiator. In doing so it appears the head gasket is blown as well.

Given the head gasket needs replacing, I'm intending to do so with the thinner head gasket offered by KTM Performance - bumps up compression. Why not, right?

What, if anything, is the downside?

Thanks for the input. Great site, good people. Cheers.
I've been searching for an answer to this question everywhere... what I can say is from what I see they seen to be pretty reliable. Also looks like there are no problems with engine knocking or detonation. Have you put them on? How is the engine feeling?
 

Icehax

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I have never had a downside to this modification other than the labor involved to install it.
Nice. I have to pull the engine out anyway to adjust the valves so I will definitely get the kit and the ti retainers to upgrade the internals a little for the higher rev limit.
 

Icehax

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Nice. I have to pull the engine out anyway to adjust the valves so I will definitely get the kit and the ti retainers to upgrade the internals a little for the higher rev limit.
Update: engine's out Screenshot_20211228-180734_Gallery.jpg

Now I'm just waiting for all the pieces to arrive.
 

1JZSupra

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Make sure you check all the surfaces for straightness. There has been some past posts on dips and whatnot due to poor casting. A lot of people just use a flat surface with sandpaper technique.
 

Icehax

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Please keep us informed on that thin head gasket install.
Will do. Currently waiting for my 2 packages from gray area to arrive, one is in LA the other is in Milan (i think, no updates since it left new York on the 4th) and with covid i think both US and Italian customs are overloaded... I'm hoping to get at least one of them this week and the other probably next week, will keep you posted.
 

TVann

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Just got the bike back with decked head and thinner head gasket. More grunt, very noticable.

Also had ceramic wheel bearings installed. Much easier to push bike around, which has obvious implications for the bike at speed. I've found that, with small displacement bikes, ceramic bearings give almost as much bang for the buck as do forged wheels.
 

Icehax

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Just got the bike back with decked head and thinner head gasket. More grunt, very noticable.

Also had ceramic wheel bearings installed. Much easier to push bike around, which has obvious implications for the bike at speed. I've found that, with small displacement bikes, ceramic bearings give almost as much bang for the buck as do forged wheels.
I'd love to start working on mine, but clearly USPS decided to lose the packages... they've been in transit between the US and Italy for 3 and 4.5 weeks respectively now... hopefully I'll be able to mount the engine back on for the start of spring...
 

TVann

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Hang in there. I suspect you'll enjoy the upgrade. Good things take time.

UPS just delivered a set of Marchesini forged magnesium wheels for my 749 - from Italy. Took less than a week.....:cool:
 

Icehax

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Hang in there. I suspect you'll enjoy the upgrade. Good things take time.

UPS just delivered a set of Marchesini forged magnesium wheels for my 749 - from Italy. Took less than a week.....:cool:
Yeah UPS is fast af, USPS however... idk how you guys are able to deal with them lol, our country has some problems but at least our national post service is acceptable . Cool thing about living here is most car and moto parts come from here, for example I bought my full decat mivv gp pro exhaust and picked it up directly from the factory lol
 

Icehax

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Finally got the packages. I have now opened the motor up. Head is nice and straight, gonna clean it up really well and get on with it. I still have to wait for a couple of pieces from ktm Italy and then I'll be able to put it all back together! I'll share some pics of the insides of my engine later
 

TVann

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Hopefully yours won't overheat and blow another head gasket 50 miles after you put your engine back together....as mine did.
 

kostean

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Hopefully yours won't overheat and blow another head gasket 50 miles after you put your engine back together....as mine did.
50 miles- I had the new thin gasket blowing on 4th lap after the change (the head were freshly machined flat).

Can not blame the gasket though but the design of the head. After that one blowing, I replaced the head bolts with hardened studs and over-torqued the bejeezus out of them. Normal gasket worked the whole season that way, but I don't dare to recommend that being uncertain how much torque do the case side of the head bolt threads withstand (they are pretty deeply threaded though).
 

DavidSim

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50 miles- I had the new thin gasket blowing on 4th lap after the change (the head were freshly machined flat).

Can not blame the gasket though but the design of the head. After that one blowing, I replaced the head bolts with hardened studs and over-torqued the bejeezus out of them. Normal gasket worked the whole season that way, but I don't dare to recommend that being uncertain how much torque do the case side of the head bolt threads withstand (they are pretty deeply threaded though).
Hi Kostean, what year is your bike, just want to understand if your bike has the newer style head or not, thanks.
 

DavidSim

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Hopefully yours won't overheat and blow another head gasket 50 miles after you put your engine back together....as mine did.
I know there were problems with earlier bikes before the head was redesigned, but I wonder if part of the problem is the head bolts stretching over time too !? I like the idea of hardened studs like Kostean has mentioned above, hopefully the 2022 bikes will not have head gasket and overheating issues like earlier bikes (got my fingers crossed).

Regards to all.
 
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