Wet Base Gasket

[F-Red]

Can this be normal? Both sides. Excessive oil on the outside edge of the gasket. Seems to be seeping through.

[Jerry Hall]

The capillary action of some gasket materials allow some liquids to "wick" through the gasket.  Some guys do not like this because the gasket seems to "sweat" a little and collect dust along the edges of the gasket.  I like this capillary action because it makes the gasket "plump up" a little and makes the gasket seal better where there are microscopic imperfections in the machined surfaces.

What I see on your gasket looks like what I am accustom to seeing on 250Rs that have had the cases cut for big bore cylinders.  I do not think that oil is wicking through the gasket but the cases are flexing between the 4 studs and not keeping sufficient clamping force on the gasket where it is wet.  When the clamping force is insufficient, some of the crankcase mixture may be getting past the gasket in the transfer port areas and where there is not much aluminum next to where the cylinder sleeve protrudes into the cases.

The engine would probably pressure check ok but when the engine is running, it may have a very very small leak every time the engine fires.  I doubt that they are leaking enough to cause any lean conditions.

Did the engine run like it had an air leak?

[jcs003]

bad sealing surface??

john

[F-Red]

Did the engine run like it had an air leak?

Thanks for the explanation Jerry. As always, your dedication to detail is impressively splendid.

The engine did not appear to have an air leak. The cases are bored. I usually apply a little gasket sealer on those gaskets. This time i didn't.

What sealer is the best for oil and gas resistants?

[udontknowme]

klingersil is good stuff and what I always use.  alittle sweating isn't a big problem but you can use a small amount of sealer and the exterior sweating will probly go away. some people are super stitious about sealers that it must have a motorcycle on the label or its no good. permatex ultra black is what I always use and it does a good job. had engines leak free for years with that stuff. some of the other sealers are slippery and can in some instances make the gasket push out when its torqed down. don't use a lot or it spooges to the inside of the engine. then again you could run the gaskets dry and should be fine. make sure the dowels aren't holding the cylinder up

[2ndmoto]

I have used 1211 quite often. I like it because it goes on easily. The key to any sealer is to use minimal amount. A few drops is all that is needed for a gasket. Just enough to make it glossy. You should barely be able to see it on the gasket. If it pushes out when tightened, that's too much.

[Skeans1]

Copper coat would work as well

[Jar350r]

I did a leak down test today my 350 held 10 psi for 15min and maybe lost .5 of a psi  but I did notice a leak when I sprayed soap water on right hand side base gasket. Think it will be good for now or I guess I could just fix it since it will bug me for ever if I don't

[jcs003]

The capillary action of some gasket materials allow some liquids to "wick" through the gasket.  Some guys do not like this because the gasket seems to "sweat" a little and collect dust along the edges of the gasket.  I like this capillary action because it makes the gasket "plump up" a little and makes the gasket seal better where there are microscopic imperfections in the machined surfaces.

What I see on your gasket looks like what I am accustom to seeing on 250Rs that have had the cases cut for big bore cylinders.  I do not think that oil is wicking through the gasket but the cases are flexing between the 4 studs and not keeping sufficient clamping force on the gasket where it is wet.  When the clamping force is insufficient, some of the crankcase mixture may be getting past the gasket in the transfer port areas and where there is not much aluminum next to where the cylinder sleeve protrudes into the cases.

The engine would probably pressure check ok but when the engine is running, it may have a very very small leak every time the engine fires.  I doubt that they are leaking enough to cause any lean conditions.

Did the engine run like it had an air leak?

jerry, did you word this incorrectly, because i read it as contradictory.

[Jerry Hall]

jerry, did you word this incorrectly, because i read it as contradictory.

I read it again.  What part or parts are contradictory?

[RIDE-RED 350r]

I use a thin coating of Threebond on my base gaskets for added insurance. As previously stated, use sparingly, just enough to put a thin even coating on the gasket. Threebond/Yamabond/Motoseal are pretty much the same stuff by different names, but all work extremely well. I know that Rotax does not use crankcase gaskets at all and uses Threebond type sealant only when they assemble sled engines at the factory. It also has adhesive qualities.

I also use Threebond when I modify chainsaws with base gasket deletes.