Super Jet what is the cuase of o ring head melt down?

Another problem in a month. Took the head out to inspect the leak as the plugs had sign of water. Found out all the o rings were melted after only 4-5 rides in one month. Last rebuild I didn't order the set from ADA but used the o ring from hydraylic shop here. Was it about quality of the o ring? This time I'lll put the ones from ADA but afraid that it'lll elt down again.
 
They were made out of rubber but not for the high temp application, I believe, but they look the same as from ADA. I thought it was ok since there's water to cool down the cylinder but it turned out I was wrong. So I wondered if they are the same as ADA??
 

SuperJETT

So long and thanks for all the fish
Location
none
For the domes you need to use viton or other high-temp material. Mcmaster sells them way cheaper than ADA.

Even though it's water cooled, you have to realize the temperature of the metal at the combustion chamber side is probably 1000F+ and the water jacket side is 100-150F depending on your cooling setup, so in the middle it's going to be much hotter than a regular rubber o-ring can handle. Also, the o-rings aren't the main seal, it's the metal surfaces being flat.
 

Mark44

Katie's Boss
Location
100% one place
Buna-N is good for +250f plenty for your head seal. Viton is good for +400f over kill yes but for the price difference why not. Viton is just a little bit harder than Buna.

Mark44
 

stanton

High on jetskis.
Location
atascadero,ca
Warped head, worn shell/domes, dropped sleeve. I would guess your getting blowby out the dome causing the rubber to burn. The oring does not provide the seal! Get new domes.
 

Mark44

Katie's Boss
Location
100% one place
t

Warped head, worn shell/domes, dropped sleeve. I would guess your getting blowby out the dome causing the rubber to burn. The oring does not provide the seal! Get new domes.

I am with stanton on this one. You need to check the head and domes for flatness.

Mark44
 
Humm!The sleeve is for sure not dropped but I'll go check the domes and flatness of the head today before installing new set of o-rings.Are the o-ring for 701 and 760 the same in diameter? A dealer here has a set for 701 engine but my engine is 760 with 85 mm bore.
 
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