slight oil weep from valve cover gasket...

RockerGuy said:
That's urban legend
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I'd have to say that synthetics can leak more. I run synthetic in everything, including my highway tractor.

If you do have a leak, it will become more obvious when switching to synthetic. Syn is still the best choice for most applications in my opinion though, people that are pro conventional, are usually people that haven't torn down/inspected many engines.
 
I had the same issue with my 81 cb1000. New gaskets fixed it..

Do not use the factory torque specs! You will break a bolt i did two and i had drill it out. Hand tighten and then quarter turn more.. Run the bike if she leaks then quarter turn more and so one
 
casacrow said:
I'd have to say that synthetics can leak more. I run synthetic in everything, including my highway tractor.

If you do have a leak, it will become more obvious when switching to synthetic. Syn is still the best choice for most applications in my opinion though, people that are pro conventional, are usually people that haven't torn down/inspected many engines.
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I've done countless research on oil & filter. If it was ever a leak because you switched to synthetic its because the sludge was holding the seals together. When you switch to synthetic, you've dislodge the sludge and the oil is able to leak through. Your seals were inherently bad to begin with.

Here is some of my background on oil, I take my oil very seriously :D
http://www.gtamotorcycle.com/vbforum/showthread.php?144099-Amsoil-Motor-oil

http://www.gtamotorcycle.com/vbforum/showthread.php?143552-Kimpex-Oil-Filter
 
Triple said:
I used to think that... and perhaps it's just coincidence, but on older motorcycles with older seals, a change to synthetic immediately caused leaks for me. I don't chance it on older motorcycles.
Another observation is that, in my case, synthetics burns faster than conventional oils (meaning I have to top-up more regularly). I've been on two wheels since 1987 and have owned a number of bikes to base these observations on.
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There is no way synthetics should burn off faster!

They have a higher boiling point, that's one of the advantages thousands of people use synthetics. Why would you pay a premium if it burns off faster?

Just because you have 200 bikes that burnt synthetics faster, that is not scientific & credible evidence. Be very aware that some oil manufacturers lable their oil synthetic and they're not a true synthetic, for eg. Castrol synthec, Shell T6, etc
 
Synthetics in an older, worn engine will burn off faster as it will get past rings and valve guides because (a) it's slicker and (b) it tends to dissolve varnish and carbon that might otherwise seal up an older engine. And it's not "boiling point", the correct nomenclature is volatility (NOACK). Synthetics, especially the higher groups can be as low as 5% volatility while conventional oil can be 15% or higher.
 
RockerGuy said:
I've done countless research on oil & filter. If it was ever a leak because you switched to synthetic its because the sludge was holding the seals together. When you switch to synthetic, you've dislodge the sludge and the oil is able to leak through. Your seals were inherently bad to begin with.

Here is some of my background on oil, I take my oil very seriously :D
http://www.gtamotorcycle.com/vbforum/showthread.php?144099-Amsoil-Motor-oil

http://www.gtamotorcycle.com/vbforum/showthread.php?143552-Kimpex-Oil-Filter
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I absolutely agree with ya.

It will also make an existing leak or seep worse. The same features that allow for easier cold starting on my Pete, also make leaks more obvious.

I admire your research. I use analysis as well as part of my maintenance. I send mine to a spot in Edmonton.

I guess oil is a pretty big part of my life as well, I sell it, and have done some real world testing and give regular feed back to one of the suppliers.
 
casacrow said:
I absolutely agree with ya.

It will also make an existing leak or seep worse. The same features that allow for easier cold starting on my Pete, also make leaks more obvious.

I admire your research. I use analysis as well as part of my maintenance. I send mine to a spot in Edmonton.

I guess oil is a pretty big part of my life as well, I sell it, and have done some real world testing and give regular feed back to one of the suppliers.
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I know better than to enter into an oil debate :)

I removed the tank and plastics and gave everything a good cleaning. I also removed a valve cover bolt. Yep, the rubber washer is flatter than a Thailandese shemale. A bugger to remove to. Obviously original washers. New washers will be in on Tuesday.
 
nomad_man said:
i had a 23 yr old gasket on my radian + old grommets. Changed them all for good measure. I also recommend check your valve clearance even if it's not due for service, you are under there, can't hurt. And will give you updated records on their wear.
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Funny, when I first read this thread I couldn't help but think back to my own Radian. I couldn't get it to stop weeping oil no matter what, but then again I didn't really know what I was doing back then. Also IIRC it is pretty easy to warp that valve cover if you aren't being careful.
 
I installed the rubber washers that Honda refers to as "rubber mounts". I tightened the valve cover bolts in a "criss-cross" pattern; I set the torque wrench to 7 Nm, and then finally to 10.35 Nm. I ran it for a while, but I ran out of daylight to see the fruits of my efforts. There was still a bit of residual oil film that came out in two spots, but after I wiped it off, I didn't see any more oil. I will go for a ride after work and report on my success.

Just an FYI, the original rubber washers were about 2mm flatter than the new ones! I hope this worked. If not, off comes the valve cover and in goes a new gasket.

As an aside, this Honda is a work of art. The engine was Honda's "high water mark" in terms of air cooled technology. It all comes together in a graceful, yet functional package. Not too many late model Nighthawks around. Single rotor up front, simple drum (that works!) in the rear, cable clutch, hydraulic valves, air-cooled, and minimal plastics. You can't get much more maintenance-free than this! :) O.K. if it was shaft drive, even better, but chains are dead easy to clean and lube (got it down to a fine art).
 
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I have the same issue on my FZR250RR ..... in my case it was actually slightly bent cover. Have you tried to check whether the cover is absolutely flat? If there's a little bent it will create an uneven pressure doesn't matter how carefully you torque the new bolts.
 
Just an FYI, that all is well. No more weeping gasket!

However, I won't lie, my first attempt utterly failed and the dang cover was weeping in more places! I took a deep breath, went back at it and popped off the valve cover. I spent the entire day on Saturday (6am to 3pm) cleaning off the original factory gasket adhesive on both the gasket itself and the valve cover. I had no choice as OEM gaskets were on backorder until the end of May! What a royal pain in the a-$$! I also had to scrape off stubborn remnants of grey RTV sealant around the half-moons that I applied earlier last year as a "quickie fix"... another pain in the a-$$! In the end, I reused the gasket (like new when I was done), thoroughly cleaned the valve cover and all the mating surfaces, and inspected the upper part of the engine (like new). I also changed the oil. She's now as dry as a bone, and I don't expect to ever go back in there for the life of this motorcycle -- as she's got hydraulic valves.

I used a VERY THIN coat of clear, high temperature silicone sealant on both the upper and lower parts of the gasket and torqued the valve cover bolts BY HAND (finger tight, quarter turn). I noticed that the bolts seemed overly tight when I applied 10 Nm of torque using my torque wrench during my first repair attempt.

Lesson learned... there's no easy road to follow when it comes to solving valve cover leaks. Spend the day and do it right.

Thanks for all your help.

BTW, now that I'm a pro (virgin baptized by fire), I am willing to help anybody in the GTA with a similar project.
 
Oh, and I also installed my "Tool Tube" while I was in there! :)

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It came with an aluminum gas bottle. Added "peace of mind" on longer excursions.
iSale.jpg
 
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Good to see you got it sorted. That's a nice looking bike.
 
DJM said:
Good to see you got it sorted. That's a nice looking bike.
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Thanks. I searched high and low for a mint condition late model CB750. I come from more sophisticated motorcycles and wanted something 'old school' and simple to maintain and operate.
Problem is, it's neither a cruiser nor a sport bike... I just don't 'fit in' :)
 
There is no mechanical reason for the valve cover gasket to leak oil. There should be atmospheric pressure inside he valve gallery, so there should be nothing to push the oil out.
Check that you DO have positive crankcase ventilation.

... oh and don't use silicone to hold that seal, use something like Threebond 1194.
 
bitzz said:
There is no mechanical reason for the valve cover gasket to leak oil. There should be atmospheric pressure inside he valve gallery, so there should be nothing to push the oil out.
Check that you DO have positive crankcase ventilation.

... oh and don't use silicone to hold that seal, use something like Threebond 1194.
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Over time, the valve cover washers, that provide positive pressure on the seal, dry and flatten out. My washers were literally half the thickness of new washers. These are what caused the leak. The winter just set it off. Gravity is all that is required to "push out" the oil when there's microscopic gaps between the gasket and mating surfaces.

The high heat silicone I used (and designed for gaskets) was recommended by an experienced long-time mechanic. I trust his judgement. BTW, I have used Threebond in the past, and it is also an excellent product.
 
Triple said:
Over time, the valve cover washers, that provide positive pressure on the seal, dry and flatten out. My washers were literally half the thickness of new washers. These are what caused the leak. The winter just set it off. Gravity is all that is required to "push out" the oil when there's microscopic gaps between the gasket and mating surfaces.

The high heat silicone I used (and designed for gaskets) was recommended by an experienced long-time mechanic. I trust his judgement. BTW, I have used Threebond in the past, and it is also an excellent product.
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GRAVITY?????
How does gravity pull the oil sideways through the seal?
The ONLY way oil is getting pushed out of the valve gallery is if the pressure in the valve gallery is higher than the pressure outside the valve gallery. The valve gallery, actually the whole motor should have one bar or less of pressure inside the cases. Less is better, negative pressure is best.

Honda gave you a nice big thick soft neoprene gasket that compresses to seal the valve cover so there should be no "microscopic gaps between the gasket and mating surfaces" if you apply the recommended torque to the valve cover bolts.
So no need for silicone.
As long as the "washers" are not so flattened to allow the bolt to bottom in the hole, they weren't your problem in the short term. The purpose of those "washers" are to isolate the valve cover from the vibration of the valve train (in case you didn't notice the valve cover bolts go into the cam caps). In the long term, if those "setting rubbers" (that's what Honda calls tham) are flattened out and hard, the vibration would be transmitted from the valve train to the cover and then flatten out the big o ring and loosen that joint, causing an oil leak.
Honda does not call for any sealing compounds on that gasket, but that big "o ring" never sits flat in the groove so I use Threebond to glue it into the groove before I install it. When you remove the valve cover again, the "o ring" stays in place in the valve cover and you never have to putz with it again.
 
nomad_man said:
i had a 23 yr old gasket on my radian + old grommets. Changed them all for good measure. I also recommend check your valve clearance even if it's not due for service, you are under there, can't hurt. And will give you updated records on their wear.
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Been a long time since I've seen mention of a Radian, was my first bike and I miss her. Hope you still have it.
 
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