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CB750 K3 Oil leak

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Bryanj:
With oil all over it does suggest that either the head or block is not flat or that they are not being clamped together enough by being held too far apart. I know that there are several different lengths of dowel pin, perhaps they have been mixed up? Try fitting the head to barrel with no gasket---it should allow the mating surfaces to touch ensuring enough squish of gasket and O ring

sim2011:
Update
I've taken the head and barrells of to SEP to be checked out so I'll let you know what they find.

I managed to find the original Honda head gasket and its mighty different to what Honda supply today See pics , the 1973 one also had gasket sealant around the cam chain tunnel the 2010 one doesn't !! The 2010 one is also bereft of those copper sealing rings .
Also I have noticed that on the 73 version all other holes (not the copper Ones) have the same sealant applied as the can chain tunell
Any thoughts on this will be welcomed.

K2-K6:
Hi again. To me that would confirm that you need a sealant at key points if not all (I've always covered total area) on any gaskets pattern or otherwise.

These are my reasons:- Honda clearly designed (original gasket proves it) to have some type of sealing additional to the gasket material around the oil ways.

I don't believe that sufficient torque can be exerted to do it totally dry with no additional sealant of some sort (copper rings, factory applied sticky-bits).

If you don't have that original spec of gasket OR something superior to it you'll have to use a substitute.

You can't increase the torque without stepping outside the original design spec, anybody that knows anything about the engineering design process will tell you that looking at this design (layed down in 1967 ish) was an absolute masterpiece then and still is an example of how to make a first off reliable engine from scratch; just one example is the stud design that is waisted (thinner) in the centre than at the threads to give equal torque load over the whole length and cross-section of each stud!!! also how the bottom threads are buried down into the casing so that the load is pulled from further within the material again to spread load indicates how thorough the design team went to work.

To me, the risk of using Blue Hylomar is only to avoid ANY loose sealant floating around as it survives in oil. The rest is all upside, as previously posted (by rigwit?) this stuff is seriously good.

With a nice new tube you can get a really thin spread coating onto the gasket, it even looks and feels like the original coating when it's dry.

Be interesting to see what your barrel / head inspection shows, let us know.

Maybe a bit too enthusiastic design appreciation there, maybe should be filed under "soapbox" but they are really good...............really.

Bryanj:
I dont ever remember seeing a Honda gasket with copper rings in it

Spitfire:
Never seen copper rings either, but have only worked on CB750's up to K2 and F1/F2.

Cheers

Den

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