O ring on KZ1000J cyl. block or silicone?

I'm thinking of replacing the large o-ring around the timing chain tunnel with silicone. What is the most successful method of applying silicone to do this. I was thinking of applying it thick enough to match the thickness of my new OEM head gasket and let it cure completely
Any thoughts?

Barney

I've had OK results just slathering the o-ring in black RTV and assembling.

Be sure your problem isn't just that you're not re-torquing the cylinder head nuts after the first few rides. That head gasket will compress a lot initially.

The problem with the o-rings themselves is just that they're too damn thin. You can shop around and use the thickest one. Or you could make your own. Here's an interesting technique:



I'd love to go to a one-piece gasket myself, but have never found one that I was certain would fit. Once you go to a big bore kit, there are plenty available, but not so much for the stock bore.

Jacklberry I don't think that method of making silicon O-rings would work since the o ring im talking about is a unusual shape

barney wrote: Jacklberry I don't think that method of making silicon O-rings would work since the o ring im talking about is a unusual shape

That's precisely why it would work. You'd just have to make the mold in the same unusual shape instead of a circle...

The problem with just slathering RTV in there and bolting on the head is that

1) It gets everywhere and is a PITA to clean out the next time
2) Unless it actually adheres to the surfaces, then it's just as useless as a too-thin rubber o-ring.

By making your own in a mold, you can theoretically make it thicker so that when installed it is compressed and the elasticity of the rubber is what makes the seal. This is how the stock o-rings are supposed to work, but they're often manufactured too thin.

FWIW, I just put a head back on with just the aftermarket 2-piece gasket and aftermarket o-ring and so far have no signs of a leak. I think I just got lucky this time and got either a thicker o-ring or a thinner head gasket.

I'm done with O rings forever. If you get the big bore head gasket, it will work and fill the groove with silicon, put it together wet. No leaks and the slightly larger bore area won't be a problem
Steve

swest wrote: I'm done with O rings forever. If you get the big bore head gasket, it will work and fill the groove with silicon, put it together wet. No leaks and the slightly larger bore area won't be a problem
Steve

Don't you think a 73mm bore head gasket on 69.5 cylinders would hurt compression? At least until the gap fills up with carbon, which could be a long time. Most of the big bore gaskets I've seen are copper too, which requires "o-ringing" the cylinders.

Steve the motor is .5mm overbore and im using OEM 2 piece gaskets. How would II applyit with a two piece?

I just got home. Long hot ride. Don't know how I double posted the pics. Fixed now. I'll get back to you.
Steve

barney wrote: Steve the motor is .5mm overbore and im using OEM 2 piece gaskets. How would II applyit with a two piece?

If you are using a 2 piece head gasket you MUST use the rubber 'O' ring.
Just using silicone is no substitute, it will NOT do the job of the 'O' ring and WILL get blown out by crankcase pressure causing a major oil leak.
Only use silicone on its own in the groove when using a ONE piece gasket.

I had to pull down my engine specifically due to the amount of oil leaking out from under the head. The reason was that PO had used silicone in place of the o-ring, the silicone had gone brittle, blown out and leaked.

There's nothing wrong with the o-rings - they're specifically designed to do that job.

And they leak, just ask my left foot. :whistle:
Steve

Zed. Is there really enough crankcase pressure to blow out a properly applied top quality silicon in the timing chain tunnel o ring groove ?