Topic: 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

[denward17]

Could be the valve guide seal, could be rings.

Slight chance of 0-ring leaking between head and cylinder.

Compression test?

Does the valve wobble in the valve guide by hand?

Hopefully more experienced guys will chime in.

[bryanj]

O ring way too far away as they are at outer ends

[denward17]

O ring way too far away as they are at outer ends

Good point, I was thinking about the 750.

[Little_Phil]

Did you check the valve guides for wear? On my 78 model all the ex guides showed wear and two very worn. Was cheaper to by replacement head.

[happynen]

Could be the valve guide seal, could be rings.

Slight chance of 0-ring leaking between head and cylinder.

Compression test?

Does the valve wobble in the valve guide by hand?

Hopefully more experienced guys will chime in.

Compression test showed all cylinders having the same pressure, so guess rings and valves shall be ok.

It does wobble a little, but doesnt seem to be any bigger play than the others.

[happynen]

Could be the valve guide seal, could be rings.

Slight chance of 0-ring leaking between head and cylinder.

Compression test?

Does the valve wobble in the valve guide by hand?

Hopefully more experienced guys will chime in.

Compression test showed all cylinders having the same pressure, so guess rings and valves shall be ok.

It does wobble a little, but doesnt seem to be any bigger play than the others.

Did not, will check for the way to check it for sure, thank you. Saw the guides cost just a few bucks and are quite easy pressed in. Is thinking of changing them and keep the same head a bad idea?

Thank you!

[bryanj]

Then you need the special  reamer and seat refacer

[HondaMan]

Yeah, like BryanJ points out: you can't just replace a guide. It changes the angle of the valve due to the distortion of pressing the old guide out and new guide back in. The seat (and often the valve guide's diameter) must be cut to match. The valve stem-to-guide clearance is TIGHT in this engine, at NO MORE than 0.0012" on the exhaust valves when new, and more than 0.0018" is seriously worn-out status. The guide wears in an oval shape, following the angle of the rocker arm above it.

[grcamna2]

Probably worn guides.
The valve guides all have one 10x1.6mm O-ring each,which sits under each valve guide and it's good to be sure you have them also along with the new guides.