Topic: are these o-rings important?

[mazingerzeca]

Hello all.
These o-rings are on the valve guide of my honda cb125s. When installing the new valve guides, the guy on the machine shop didn't install these o-rings that go between the valve guide and the cylinder head. I don't know if I will have oil leaks without these o-rings. I wouldn't like to get the valve guides off just to install these o-rings, because the taking off and entering of the valve guides can do some damage on the cylinder head. Well, are these o-rings essential or can I go without them?

[Tim.]

Yes they're essential.  Honda wouldn't have bothered with them otherwise.  Take the head back to your machinist and have them install your o-rings.

I had a machine shop do a valve job, and they forgot to install the new valve stem seals I gave them.  Of course I couldn't really tell once I got the assembled head back, and completed my full rebuild of my 550F.  New pistons/rings, the works.

A few months later I started burning oil.  Seals failed, oil through the guides, glazed cylinders... all leading to another complete rebuild of the engine.  New pistons/rings all over again in a fresh cylinder block.

Just be glad you found out he didn't install the o-rings.  Did he forget to do it, or did you forget to give him the rings?

[mazingerzeca]

Thank you for the advise.
It was my fault. When I was checking the partslist I saw the o-rings, but I didn't see them on the cylinder head. Of course, because they were under the guide, but I couldn't imagine that it could be a o-ring there, so I thought that it was referred to a different part on the parts list, or a mistake.

[Tim.]

I remember thinking the same thing when I saw them, but they are important.  You will get oil leaks and that in particular is one area you do not want oil leaking.

Does your machinist work on motorcycles much?  I think many of them have these o-rings.  Pressing the guides out and back in again won't cause any damage.  They are designed to be removed and replaced without damaging either head or guide.  Should take him 10 minutes to press all 8 out and press them back in with o-rings.

[mazingerzeca]

Well... I think they don't work on motorcycles too much. Mainly on cars and trucks, sometimes two-stroke spanish bikes. I don't think they make a bad work, but they are not as anal as me with my own bike.
Yes, they have the o-rings. I think it won't be necessary to get the guide all the way off. I'v tried with the old guide and the o-ring enters from the upside, and stretching it, it passed the prominent part of the guide, so maybe they can drive the guide off 2 mm, pass the o-ring and leave it on its place.

[Bodi]

The guide is a press fit, and leaks would be miniscule if any at all. I have left these things out with no problems.

[crazypj]

Your better off leaving them out.
If you remove he guides you really shouldn't re-fit them again, they will more than likely come loose when engine gets hot. They should be a shrink not a press fit, head needs heating to about 350 degrees for fitting or removal.
 You may also need oversize guides and ream holes in head if you try taking them out again. ( get early Goldwing or CBX guides and have them modified if Honda genuine are not available oversize)
 You can also get phosphor bronze guides made reasonable cheap.
PJ

[754]

Re and re of guides in a clean hole is not what wears out the holes.

Pushing them up part way and installing, may be the only way to do it WITHOUT having to touch up the valves.


They should noy leak unless the guide bore is scored, but Honda is extra careful and likes to produce an oiltight long running product..

[Tim.]

Well, now I'm all curious.  Why does removing and reinstalling the guides require 'touching up' the valves?

Doesn't sound like there's a clear concensus, but if they can press up the guides a little bit as you've suggested and 754's endorsed, that sounds like the best bet.

[mazingerzeca]

I think that if you remove the guide once the seat has been cutted, when it enters again, it enters in a different position, and the valve doesn't seat well.

[crazypj]

repeated removal and refitting enlarges the holes in the head. there is a limited number of times you can do it before you need oversized guides.
I worked with this stuff daily for over three and a half years so have some experience. (motorcycle cylinder head and crank reconditioning, single cylinder,offroad and ATV, etc.)
PJ