1978 CB400 Hawk Head Bolt question

Chim

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Location
New Hampshire
I'm chasing oil leakage on this 78 CXB400 Hawk and thought head gaskets would in order. In removing the head bolts, the outside four bolts are pristine, but the four interior bolts were either exposed to oil leak or are contributing to the leak problem... threads packed full of grimy oil residue. I realize they have external exposure (you can see them as you pull them). What can I do to help with this going forward when I reassemble.? Should the threads be sealed somehow? thanks for your help!
 
Look at the base of the cylinders. Are there 2 channels running from the cam chain tunnel to the front head bolt holes? If so then you want to clean them and fill with JB Weld. Those channels only exist on the '78 models.
In '79 the inner left cylinder bolts got a rubber sealing above the threads, might update those 2 bolts.
As for the rears I seen what you're talking about and the only thing I've come up with is the copper sealing washer at the top wasn't sealing well or possibly the torque was right. I retorque head bolts on every fresh engine after the 1st run and again after @500 miles.
 
Thanks for your help… I had read somewhere about the rubber sealed head bolts. The upgrade makes sense. Wonder why you wouldn’t do both inners..?
Thanks
 
LongDistanceRider said:
Good question with no answers
Click to expand...
I see you've got a couple of 400T's... your 79 has the grommet bolts but the 78 doesn't? I'm thinking the grommets would block that channel which you've mentioned is only on the 78 and should be filled in anyway. What do you think the grommets actually do?... is it to keep the threads from exposure to the elements (through that air passage in the head)? And... wouldn't a very thin layer of a sealant like UltraGrey serve that purpose? Sorry for all the questions... I just don't want want to block oil flow that is supposed to be there but at the same time most of it comes out the front and back near the cylinder/cylinder head seam. Appreciate your help and responding... thanks
Also: found the upgrade bolts on Partszilla.... listed them under the 1980 Hawk.
 
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My theory on the rubber is to prevent water from seeping down into the threads. Note that when parked on the side stand the left cylinder is low side and the front inner bolts are exposed.
The only bolts that serve as oil passages are the rear outer bolts. It can't hurt to use the UltraGrey on the bolts but it would need to be dry and not on the threads before installation.
 
LongDistanceRider said:
My theory on the rubber is to prevent water from seeping down into the threads. Note that when parked on the side stand the left cylinder is low side and the front inner bolts are exposed.
The only bolts that serve as oil passages are the rear outer bolts. It can't hurt to use the UltraGrey on the bolts but it would need to be dry and not on the threads before installation.
Click to expand...
Thanks, I went ahead and ordered the two bolts with rubber for the left interior, figuring there is a good reason they don’t put them on the right. The outer bolts were fine… also OE sealant washers. Thanks for all your info. 👍

Also, look at this video that shows the problem clearly...
 
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