Topic: Oil leak above the head gasket

[Stoli]

Model: CB750 K8

About 2000 miles after a rebuild, I noticed a little oil on the head fins after a ride. Not too bad, but a few drips would result. This is not a pic of my engine, but just to show where the oil leak is -



- Area A seems to be where the heaviest concentration of oil is after a ride.
- Eventually it will drip from point B after resting on the side stand.
- No oil above or below, so the head and valve cover gaskets are good.

Soooo ...  You assume pucks or valve tower stud, right? That's what I did, so I recently pulled the engine, took off the valve cover and valve tower assembly, sealed the studs with some high temp thread sealer and the pucks with some non-hardening gasket seal, re-torqued the head nuts while I was in there and then put her all back together.

First ride - same exact leak.

Ran a q-tip up inside the puck area and the hole where the leftmost valve tower stud threads into and it came back dry. The immediate area around the spark plug is also dry. 

The only place left that I can guess where the oil might be coming from is the nut/washer that is on the cylinder stud in front of the spark plug. There looks to be a little oil around the base of that (although it is a low point in that area so inconclusive at best). The rest of the plug cavity is pretty clean.

So my question(s) -

- Is it possible/likely for oil to come out of that cylinder stud?
- If so, what is the easiest way to seal it?

I haven't tried yet but it looks like I might be able to get that nut and washer on and off without removing the valve cover, so I might be able to remove and retorque without removing the engine again.

Thoughts?

[flybox1]

stumped. 
time to break out the spray foot powder 

[KayOne]

Don't know about area A, but I had oil in the B area from the valve cover screw threads that are open on the bottom (pretty sure all but 4 cam cover screws are open to the bottom). Used thread sealant when I assembled the motor initially too. Had to remove the two forward screws nearest the outside of the cam cover, clean holes and threads with brake clean and reseal...holding up so far.

[Stoli]

I've been studying all the oil passages and it seems very unlikely that oil would be around that particular cylinder stud and now that you mention it, the oil does seem to be concentrated directly below the leftmost valve cover screw. Man I hope that's it. I really don't want to pull this engine again. My stands are busy holding other projects.

[mcswny]

I'm sure its a long shot, but did you check your valve tappat inspection gaskets? Might as well as throw out the brain dead easy options first...

[Stoli]

I'm sure its a long shot, but did you check your valve tappat inspection gaskets? Might as well as throw out the brain dead easy options first...

Yes, they look fine as does the valve cover gasket. I'm putting my money on the valve cover bolt holes. It is most likely the one on the end but will clean and seal all 3 of them. Unfortunately it'll be another week before I can test it out.

[mcswny]

I'm sure its a long shot, but did you check your valve tappat inspection gaskets? Might as well as throw out the brain dead easy options first...

Yes, they look fine as does the valve cover gasket. I'm putting my money on the valve cover bolt holes. It is most likely the one on the end but will clean and seal all 3 of them. Unfortunately it'll be another week before I can test it out.

Is it stripped or just dirty? If stripped heli coil or time/sert

[Stoli]

I don't think it is stripped or dirty. When the head heats up, I'm guessing the threaded hole expands enough for oil to easily seep down between the bolt and the threads. Technically, the valve cover gasket should be preventing oil from ever getting to that area but I probably have a slight imperfection, maybe a small gouge in the head or valve cover that is allowing the oil to get by the gasket in the area around that bolt on the end of the cover.

[mcswny]

I don't think it is stripped or dirty. When the head heats up, I'm guessing the threaded hole expands enough for oil to easily seep down between the bolt and the threads. Technically, the valve cover gasket should be preventing oil from ever getting to that area but I probably have a slight imperfection, maybe a small gouge in the head or valve cover that is allowing the oil to get by the gasket in the area around that bolt on the end of the cover.

Ahh that's a bummer.

[Stoli]

Sort of, but the fix is actually easier than installing a heli-coil. Assuming I am correct, a little thread sealant should do the trick and there is no need to remove the cover. There shouldn't be much if any pressure under the valve cover so the seal is just working against gravity.

[mcswny]

hope thats it, good luck! keep us posted

[madScientist]

Question...when you had your head off I assume being rebuilt...did you remove the cam tower studs?

If so there's a possibility oil could be seeping past the threads. What I did with mine is put some permatex sealer on the threads as I installed them.

[Stoli]

On the initial rebuild, I didn't get that memo, so, yes I removed the studs and no, I did not seal them during reassembly. That is why my first thought was to pull the valve towers and seal those studs as well as the pucks. I did that recently but it didn't fix the leak. So the only other holes in that area that I know of are the cylinder stud, spark plug and valve cover bolts. The valve cover bolts make the most sense.

[evanphi]

I'm keeping a close eye on this... I think I have a similar issue.

[Stoli]

Still have a leak. To recap, I have sealed the pucks, sealed the valve tower studs and sealed the 3 valve cover bolts on the end, There is no oil leaking from the valve cover gasket or above it and the head gasket is good as well. Only places left that I can tell are the cylinder stud and the bolt as shown in the pic. for those that noticed, the bolt is not standard size. The stock was stripped so I tapped with a 1/4" bolt and used that for the rebuild. Anyone have any thoughts? Guess it's time to break out the Dr. Scholls.

[flybox1]

Positive it's oil?
Exhaust blow by from a bad ex. seal depositing there?

[Stoli]

Hey Fly,

Well, its brownish and slippery. Curious about the exhaust blow by. What would that look like?

[grumpy]

exhaust blow-by is soot very black soot.

check the head cover gasket seal around the cam tunnel above plugs 2/3 (you'd be surprised how far oil will flow)

also, try smooshing some epoxy putty or high temp RTV into the the open ends of the cam tower studs - in case the thread sealant failed.

is there any oil present on the cam chain tensioner cover and/or the fronts of the carb bowls?

[Stoli]

Well, it isn't sooty at all. My engine is very clean so there is no mistake there. Still looks like this only it's in the bike:



The head gasket cover is spotless all the way around. Also checked the carb bowls and tensioner area and all are clean.

Just the few drops of oil that show up between the bottom 4 fins on the head in the area shown in my first pic. I'll try the putty suggestion but that orifice seemed pretty clean after my last ride.

Is there any possibility at all that oil can come up and out of the cylinder stud or bolt that my previous picture is pointing to?

[flybox1]

head gasket on backwards creates an awful alignment issue right between plugs 2&3, and possible gasket tears when installing the cover bolts in that area. 
could any oil be weeping out of this area and riding turbulence pushing it to this side?

[Stoli]

I've run a clean white paper towel all over the cover gasket area as well as the rest of the head and the only place that it picks up oil is on those fins. Can the wind clean it off that well? Maybe. I guess that is why the foot powder test is probably necessary.

Funny you should mention the gasket. I did in fact have it backwards when I last reassembled the head cover but I noticed it before I put the screws in, so I am positive that the gasket is installed correctly. It is one of the few things I am sure of.