Barrel to Caes seal, and small indent

[kd]

Cometic has .010 &.020.  They will also make other thicknesses on request for no additional fee.  You have to call them to discuss what dimensions of stock they have.  You can also do like No Cents and I (at least) did. and add a paper wafer with aviation gasket cement. Again, adding a gasket "cement / glue" that has time to set before assembly is complete, seems to me to be looking for failure.  There are too many better options. 

[Don D]

For those that just have to have their goop the SLS Cometics can be used with a light coat of copper coat or hylomar or derivatives.

[kd]

    And a very light film application is all that is required as it will be squeezed out to a zero build-up.

[1340evo]

Just re-reading the instructions for the gasket I have and what it actualy says is 'needs no additional sealants' so does not say don't use it. I have some Loctite 5900 flange seal that I know through experience is impossible to get off, so it will get a dab of this on the indent, and again on the case joint, job done. I have cover an area on a .020 gasket I had spare just to see what happens and if it degrades the existing silicone bead any... job done.
Have also finished my fly cutter now so will be skimming the heads down to 78cc tomorrow... then Bob it back together and ride   

[kd]

What does the Loctite 5900 do at sustained temps of up to 400 degrees?  It's silicone sealer.   You are joking, right?  Have you looked at this ?

[1340evo]

It's good for 200 deg C.. so 392F.... what temp do you think it sees down there?
We use on flanges that sometimes see 200c and it lasts...

Anyway, this arrived today if you think its better. Will it work with the silicon bead? I've put some on my test gasket to see what happens

[kd]

I guess you're gonna find out.  You can let us know how your experiment goes for you.

[1340evo]

see above.. I tried the Permatex on the silicon on the gasket... see what happens after 24 hours.. any idea if its okay ?

Did you take a look at this? https://hylomar.com/en/mwdownloads/download/link/id/130/

[kd]

I think what ever you try will probably be captured inside the bead and possibly not allowed to escape (at least evenly if at all).  To me that means build up.  I have no experience with the James Base gasket you have and would probably follow the gasket manufacturer's instructions if I had no other gasket choices. I suggested the aviation cement because I thought I understood at the beginning of this you were using a single layer steel or paper composite gaskets.

[1340evo]

Ok... let's see what happens

[nmainehunter]

Today I had to take my front cylinder off due to the failure of the James base gasket, same as the one shown. I got less than 50 miles on it since taking it down this winter to do some up grades. I've been doing this for years and never had a failure like this. I checked my head bolts for torque and all was good. This wasn't just a seep. I expected to see a torn gasket but that wasn't the case. What I did see that was odd, was the red silicon was squished out in the front and the rear of the cylinder, weird.

[1340evo]

They did have problems with early ones doing this by all accounts. Any idea when your gasket was made?

Or oil on the sealing face could see them slide out sideways?

[nmainehunter]

I don't know how old those gaskets are. I did order new Cometic head gaskets but the others have been in my collection for a while, years. I'm going Cometic top and bottom on the do over.