Valve Guide Leak?

[Happynen]

Hi guys,

Brought home project last year, incomplete CB550K ‘78, did total rebuild (seals, rings, plugs, oil, lapped valves..) and started riding it, everything went just fine, but than.. my head started leaking at the exhaust port at cyl no. 2. Cylinders had the same conpression, spark was dry, oil level in the middle of stick gauge, but the oil just kept on weeping out hard (checked at idle only as the weather turned shait).

Disassembled the top end to find out the seals were just fine, combustion chamber was dry, but found out the leak is coming through the valve guide, even though it was set with new sealing like a year back.

My question is- shall I think it is just a errored piece of valve sealing or is it possible the oil could be leaking through the guide itself? Have you ever faced the same thing? Whats is the course of inspection you would recommend before start acting? Just would like to avoid extra work not needed eventually resulting in me causing even more damage as I go:)

Thank you for your help in advance and sorry in case I have missed already existing thread, kept on searching the whole week long, but have not found anything focused on such a thing.

Thank you and have great day:)

Jiri

[McCabe-Thiele (Ted)]

Iirc the guides if they are removed have an end seal.

Not the outer valve stem seal.

[Bryanj]

If you or a po did not take extreme care when fitting the cam cover it is possible for a rocker arm to push the top of a valve sideways and crack the valve guide which may be your problem.
As all 500 and 550 sohc heads are the same it may be cheaper to locate a used one, i have a totally bare head i may let go

[Happynen]

Iirc the guides if they are removed have an end seal.

Not the outer valve stem seal.

You mean that o-ring, right? I was thinikng the same, but thought the press fit of the guide itself shall seal it just the way how tightly is fitted in..?

[Happynen]

If you or a po did not take extreme care when fitting the cam cover it is possible for a rocker arm to push the top of a valve sideways and crack the valve guide which may be your problem.
As all 500 and 550 sohc heads are the same it may be cheaper to locate a used one, i have a totally bare head i may let go

Im not sure about the POs procedures really, but the engine was stripped down before for sure. As only one of these seem to be faulty, is it bad idea to think of changing it? Also got the head decked, so would like to keep it.. but if getting another one would make better sense, thats the way I guess too..

[McCabe-Thiele (Ted)]

Iirc the guides if they are removed have an end seal.

Not the outer valve stem seal.

You mean that o-ring, right? I was thinikng the same, but thought the press fit of the guide itself shall seal it just the way how tightly is fitted in..?

If the fit was enough then why is there a seal/Oring ?

[Bryanj]

Changing a guide is not that straightforward, the bore has to be reamed and its not a standard size then the valve seat has to be remachined to suit