slight oil weep from valve cover gasket... | GTAMotorcycle.com

slight oil weep from valve cover gasket...

Triple

Triple

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After 5 months of sleep, I started my CB750 Nighthawk. 5 cranks of the starter and she hummed to life. I noticed a 1 cm section of the valve cover gasket with a slight bit of oil film. Can this happen after simply storage and cold weather? Wait and see if it goes away with warmer weather, or reseal? What is your experience?
 
I would clean the area and run the bike to see if it continues to leak, maybe try to re-torque the valve cover
 
RonnieRev said:
I would clean the area and run the bike to see if it continues to leak, maybe try to re-torque the valve cover
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This but find out the torque specs and don't over torque (easy to strip). The constant warm-cold transitions we've had this winter cause a lot of constricting / expansion. Take a look at your driveway after starting your car and you'll occasionally see some small drops of coolant down there on the coldest of days as the hoses just don't fit right until they warm a bit. My bike seeps a tiny bit of coolant if it's really cold out in the garage and it hasn't been run in a while.
 
a 2001 cb750 is a bit new to have valve cover gaskets rot on. has this cover been removed in the past?+

I'd just remove the cover, clean it and put a thin strip of rtv and it should hold well. Or buy a set of new gaskets.
 
frekeyguy said:
a 2001 cb750 is a bit new to have valve cover gaskets rot on. has this cover been removed in the past?+
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That's a 13 yr old bike
 
frekeyguy said:
still too new for dry rot. i suppose it is possible.
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Agreed its possible. But as you mentioned I'm willing to bet it was the previous mechanic who didn't use silicone.

The important part for this is the U-corners on the valve cover
 
I'll pop the cover when the weather is warm and reseal with some rtv sealant. There's no dry rot to be found on this beast. She saw a sheltered, pampered life.
 
RonnieRev said:
I would clean the area and run the bike to see if it continues to leak, maybe try to re-torque the valve cover
Click to expand...

Thanks, I will try that first. I have a shop manual, so I have the correct torque values.
 
Just to keep you in the loop (and I appreciate your help), I ordered 8 new rubber washers that go underneath the valve cover bolts. Because my Nighthawk is a 2001, the odds are that these washers are somewhat flattened with age/heat. My thinking is that if I replace the washers, there will be a little more "squish" before the valve cover bolts bottom out (as you know, you can only tighten them so far). Basically, I will replace the rubber washers and re-torque the bolts (7 foot pounds?) and see if this stops the sweating. This is worth a try, as the gasket appears perfectly fine from the outside. If this fails, then I will replace the gasket. What do you think?


frekeyguy; I tried to message you, but your inbox is full.
 
Grommets are indeed the right solution. Inspect your gasket before you put it in. Don't forget to retorque if starts weeping again. Also synthetic will leak more.
Torque settings - check the manual
 
You can see where the rubber washers go (#7)...

HJ540003.gif


I will not bother to lift the valve cover to inspect the gasket unless this idea fails. I am certain that the original gasket is like new.
 
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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.


grommets.
:
IMG_20140216_182850.jpg



outer bolts:
IMG_20140216_164305.jpg

While i was at it, i repainted the cover. Grommets go on the inside of the valve cover for radian.
IMG_20140223_141252.jpg
 
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Your photos just answered my question! Thank you.

The valve cover hold down bolts have a shoulder on them (as in your photos) so you can only tighten them down to a point and they stop. The rubber washers clearly shrink/wear away with time (again, as in your photos) so the cover will not go down as far. Often the gasket is not the cause of the leak but these rubber washers are too thin!

BTW, my 2001 Nighthawk 750 has hydraulic valves! :) Part of the reason why I bought it! ;)
 
Oh... and... my Nighthawk has never seen synthetic or synthetic blends. I swear by quality dino oil and regular 3000-5000km (max) oil changes.

Post a photo of your Radian... they're cool bikes!
 
Perfect, glad i was able to help. You can clearly see the wear on the rubber grommets + rubber washers from the age.
I kept the old gasket too :D just in case. While i think it should be ok to reuse it, i do believe they tend to get squished with age :)
Also with regards to torque value IIRC mine was 7.2 ft*lb
 
nomad_man said:
Perfect, glad i was able to help. You can clearly see the wear on the rubber grommets + rubber washers from the age.
I kept the old gasket too :D just in case. While i think it should be ok to reuse it, i do believe they tend to get squished with age :)
Also with regards to torque value IIRC mine was 7.2 ft*lb
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I was going to go with 10 Nm... which I believe is about 7 ft lbs... so I'm confident with that torque rating. No ham-fisting with me anymore... learned that lesson a few times!
 
RockerGuy said:
That's urban legend
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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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