Head Gasket Blown

[MuTToN_DaGGeR]

Sooo... It happened.

There are bubbles coming up in the rad and the bike gets hot in a hurry.

While I have the heart open, what else should I do?
Should I change the rings and chain?

The list so far is pretty short, just change the gasket, check valve clearance.

Any advice is appreciated!

 

[=maz=]

Look at Chad's engine kit...and have a look at Grey Area KTM's bits and pieces.

 

[MuTToN_DaGGeR]

So I now know what the issue was.

The head gasket went and was pumping air into the cooling system.
There was obviously a constant pressure build up from the blown gasket, pushing the coolant out of the rad, overflowing the overflow and not letting the coolant flow back into the radiator.

So if anyone else has the below symptoms, change the clearly faulty head gasket.

• Pressure release while opening the cap when the bike is cold.
• Constantly "overfull" overflow tank.

I hope my issue will save someone else a completely gaziboed motor in the future.

 

[A0AM]

So I now know what the issue was.

The head gasket went and was pumping air into the cooling system.
There was obviously a constant pressure build up from the blown gasket, pushing the coolant out of the rad, overflowing the overflow and not letting the coolant flow back into the radiator.

So if anyone else has the below symptoms, change the clearly faulty head gasket.

• Pressure release while opening the cap when the bike is cold.
• Constantly "overfull" overflow tank.

I hope my issue will save someone else a completely gaziboed motor in the future.

Sorry to hear. What year is your bike? How many miles?

 

[MuTToN_DaGGeR]

Sorry to hear. What year is your bike? How many miles?

Yeah man, it is what it is.

Its a 2015 Model with 36000 KM on the clock, motor never been opened.

Till now

 

[chevaliernoir]

I had it too, after few month without using the bike
I did precise measurement of engine head flatness and found that :
It was still inside ktm specification,
But the gasket blown exactly where the flatness was bad. So for me, there is a clear link between flatness and engine head gasket failure.
Just changing the head gasket would postpone the next gasket blown, but does not solve the origin of the issue.
I would not expect reliability improvement too, with thiner gasket.
The flatness of cylinder was Ok.

Flatness can be corrected by yourself at very low cost

 

[MuTToN_DaGGeR]

Im going to be sending the Head and Barrel to a machine shop to get skimmed.

This was supposed to be the daily, now the head is coming off lol!

 

[ReidMcT]

Flatness can be corrected by yourself at very low cost

Interesting! How?

I only know very crude method for checking flatness. I have a spare engine apart on the bench right now, so it is a perfect time for me to learn and do.

Thanks!

 

[MuTToN_DaGGeR]

Ill be sending it to a shop to get done, I could ask for some pics if they remember?

Its the same place ive sent all my other engines to get flattened.
I was really surprised that the barrel and valves looked REALLY good, still loads of honing marks.
The ring gaps were also well within spec, the chain on the other hand seemed to have had more slack than it needed.
It started eating into the side of the engine case, that as well as the tensioner will be getting replaced.

 

[chevaliernoir]

Here is the thread I report measurement of flatness, and the cheap but effective way I corrected it : https://www.rc390-forum.com/forum/ktm-rc-390-general-discussion-forum/3192-ready-race-machine-2.html

 

[Boardinfourlife]

So I now know what the issue was.

The head gasket went and was pumping air into the cooling system.
There was obviously a constant pressure build up from the blown gasket, pushing the coolant out of the rad, overflowing the overflow and not letting the coolant flow back into the radiator.

So if anyone else has the below symptoms, change the clearly faulty head gasket.

• Pressure release while opening the cap when the bike is cold.
• Constantly "overfull" overflow tank.

I hope my issue will save someone else a completely gaziboed motor in the future.

Thanks for the advice man I currently am experiencing a slight loss in coolant and slight gain in oil level on my 2017 RC 390.. I have torn down the bike already once before to swap engine air filter, fuel filter, spark plug, clean 02 sensor, replace clutch disc plates, and water pump seals.. I picked up a high compression head gasket just in case.. and unfortunately I'll be needing to drop the engine this winter to swap out the old head gasket.. once I have the engine dropped and take the head off the engine.. is there anything I should watch out for in the head gasket installation? Thanks any bit of advice would be greatly appreciated

 

[1JZSupra]

A straight piece of glass, various grits of sandpaper, and I would consider checking to see how your valves are seating. If they are good and there are no leaks then you'll be fine. If not you'll want to lap in the valves to get a good seal.

 

[B7ACKTHORN]

Use a steel ruler and invert it to the sides and check for flatness of the head surface. If you have a boiling radiator, you have a bust head gasket.

 

[Formula390]

A straight piece of glass, various grits of sandpaper, and I would consider checking to see how your valves are seating. If they are good and there are no leaks then you'll be fine. If not you'll want to lap in the valves to get a good seal.

You can't just check the perimeter. You have to check flatness with something like a machinist square or steel rule. This is because the heads are frequently still perfectly flat around the perimeter, but are outside of the spec (0.004" if I recall correctly) on the inside... where combustion gasses can make their way to the oil and coolant passages, or oil and/or coolant can make their way into the cylinder.

 

[1JZSupra]

You can't just check the perimeter. You have to check flatness with something like a machinist square or steel rule. This is because the heads are frequently still perfectly flat around the perimeter, but are outside of the spec (0.004" if I recall correctly) on the inside... where combustion gasses can make their way to the oil and coolant passages, or oil and/or coolant can make their way into the cylinder.

Agreed. The good thing is that there are two well known areas where these things blow which helps out a lot when looking. I also use dychem on my head so that I can see the low points as I was sanding it down.