Oil leak half way up barrel.

[highboy_coupe]

Hi, are the head stud holes in the block open to the crankcase? My head gasket is dry, as is the base gasket... but I have oil on about the third barrel fin up. When the bike is running, if the bike is on the side stand I get a spot of oil on the primary cover.
I can only guess that oil is creeping up the threads on the left rear stud. I was sure I used thread lock on them!
Thanks.

[neil1964]

You have not said which bike!
It is entirely possible to have a leak from the barrel in isolation
If your barrel has been over bored it is possible for oil to penetrate around the head bolts and come through the side or even up the bolts and appear on the top of the head fins. 
So answer is yes it is possible, but it depends!!

[highboy_coupe]

Hah, sorry, it's a B40F, and it's 40 thou over. I cleaned it all off, and went for a ride, this resulted in a slightly wet 2nd and 3rd fin up. But definitely dry around both gaskets.
Is the answer just more thread lock next time? Some kind of high temp gasket sealer? I used blue hylomar but I think this is too soft.

[rhyatt]

I think you'll find that there is weepage into the studs from the 2 drain holes that take oil from the rocker box down 2 drilling through the head gasket into the barrel drain drilling into the crankcase.
I had to make a paper gasket to supplement the copper gasket and use wellseal , this sorted it totally

[highboy_coupe]

Great, thanks. If it doesn't get too bad I will wait 'till winter and then add more gasket material.

[highboy_coupe]

I am returning to the garage determined to sort this out as riding around it can get quite messy with oil blowing off the fins...

I think it's been established it's either being pushed up the threads and studs from the crankcase, or it's coming down the studs from the head gasket.

I would like to confirm what work I need to carry out to stop this, rhyatt mentioned wellseal and paper gaskets in addition to the copper gasket, but in what manner, smear both sides in wellseal and put a paper gasket underneath?

I have heard that the drain holes from the head could also be blocked with sealant (I used a very light smear of blue Hylomar on my head gasket and I know this can migrate as it stays semi liquid. I can see if there's a blockage oil is going to sit around in the head and find it's way out eventually.


While I have the head off, should I just take the barrel off and remove the studs to apply silicone to the threads? This would just be insurance in case it was being pushed up out of the crankcase.

Thanks for your help

[rhyatt]

Yes wellseal and paper gasket.
My SS80 suffered weeps from the head gasket joint despite scrupulous attention on rebuild.
O ly cured after I discovered that the new copper gasket was not as thick as the original.
Tried annealing of course.
So , created a paper gasket and made the new assembly ,
Head , wellseal, copper , wellseal , paper, wellseal and cylinder spigot upstand.
Sorted
Making sure with a piece of wire that the 2 drain holes went right down into the sump

[rhyatt]

I did try a couple of new copper gaskets, but found that even after nipping the 4 head nuts down, there wasn't much of a nip on the copper gasket.
Maybe modern copper gaskets are thinner than originals??
I did also try a wire down the drain hole from the top of the barrel joint face to ensure the wire went into the crankcase, to ensure no blockage.
I did take a while to ascertain that this "thinner" gasket was the cause, but sorted and dry now

[highboy_coupe]

That's great information thanks. Luckily I can get the head off with the engine in the bike!

[highboy_coupe]

Right, engine is all apart, the head gasket was pretty oily on both sides but it's inconclusive as it could have happened when the tension was released on the studs. I cannot for the life of me get the studs out, so my hopes are if the they're that tight then it's unlikely the oil is being pushed up from the crankcase.
Also, logically the lower fin would be the only wet one if the oil was coming up, as it would spread out as soon as it got to open air.

Rhyatt, you mentioned a "cylinder spigot upstand" in the assembly process, now am I being stupid or am I missing a part?

I noticed that the base gasket had migrated slightly and was half obscuring a drain hole. The drain holes seemed to be clear otherwise.

I am going to do as Rhyatt says, and make sure everything is sealed up top, bit it seems like of I could get the studs out then I could put a bit of thread sealer on them just to be sure.

[rhyatt]

Upstand was the only term I could think of in relation to the top face of the cylinder barrel that sticks up.
It is this upstand or spigot that the copper head gasket sits over.
I think I used a paper base gasket along with the copper gasket and Wellseal to create an oil tight head joint, trimmed to fit of course.
It is most likely gravity and oil draining down from the head , through the 2 drain holes that was weeping through the head joint , but at least you've discovered that 1 of them was obstructed by the base gasket moving.
If they're that tight, I doubt if the oil is coming up via them.
Cheers

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