The International CBX Owners Association

Kool_Biker wrote:

daves79x wrote:Aris:
I'm still scratching my head over the #1 combustion chamber/valve damage to #1. No idea how glass could have gotten in there to cause problems.

Dave

I love old photos ... looking carefully at the pic below, taken during the previous assembly of my engine, you can see the 'damaged' cylinder no 1 exhaust valve(s) in all their glory!

DSC07375 (1).jpg

So the damage was there from BEFORE, and out goes the theory this might be glass related!
Some good news al last, BUT makes me wonder why these valves were used in my newly refurbished head (a job outsourced by myself at the time, to a competent firm in the UK).
In any case I will have them both replaced so I will hone my valve lapping skills
Aris

The "damaged" areas appear to be below the contact area.....so not an issue.

What an incredible thread and amazing photos Aris.

Like many have said before me...... you went well beyond the call of duty on this motor the first time around and to have this pocket of glass beads attack #1 cylinder is truly puzzling. Frankly, there's only a couple of pockets they could have been hiding.....and I'm sure you removed both plugs to clean them out.

I hope you find the answer.

My best....... Mike

daves79x wrote:Aris:
I think the dirty little secret is that most pro shops just cut/reface the seats and install new valves. They do not hand-lap each valve.
Dave

Dave, thanks for using the correct words describing what I was beginning to 'discover' here.
Now cleaned, all my valves / valve seats look freshly cut and good for sure. But they were definitely not lapped
You can tell immediately if a valve and / or a valve seat have been lapped, by the light grey ring on the otherwise shining metal. I will certainly lap all remaining valves, using fine paste only.
Cheers, Aris

Mike Cecchini wrote: The "damaged" areas appear to be below the contact area.....so not an issue.

Mike, thanks for your kind comments.

And BTW, I agree with you above, it is evident in the posted pictures.
But, as I have a few NOS valves lying around, I will go ahead and change them any way. They are only two ...

Regards
Aris

Valve lapping was the order of the day, and in the little time I had, I did few inlet and exhaust valves Very interesting how the lapping process, in a freshly pasted valve, sees the valve rotating easily but quite rough with a distinct abrasion noise which almost completely goes away as the lapping process proceeds and the valve becomes noticeably more difficult to rotate! You get the feel quite quickly and you are rewarded with a nice 'lap mark'. I have noticed the exhaust valves are measurably harder to lap - is there any truth to it?
Best, Aris

Great therapy work. It's nice to see the gray area appear as you go along and get the feel of it.

To answer your question about exhaust valves......Yes... many exhaust valves are of a different harder material because they constantly live in high exhaust temps and they only get cooled when they are seated vs the cool temps the inlets live because they are getting a constant flow of cool intake air.

Great pics Aris..... love following your work this way.

Best....... Mike

Soooooooo,
Finished with the valve lapping today. The exhaust valves took surprisingly more time to produce a nice continuous grey 'lap ring', but otherwise the process is identical as for the inlet ones; liberally coat the valve face with fine lap paste. Starting the back and forth motion you can feel the cutting with scratching abrasion noises, somehow amplified by the head aluminium structure(?) then, after numerous iterations, end up with an almost quiet back and forth motion, measurably harder to turn than before as the paste has done its job.
Below is a typical lapped exhaust valve, which seems good to me. But, as always, I would value your inputs: Too little? Too much? Cheers, Aris

Hi Aris,

Just curious are you numbering the valves and installing the laped valve in the matched seat that you laped them in?

Jay

Hi Jay

Absolutely, see pic below. I use an old carton where I make holes and number them 1 to 24.
I then put the valves in the corresponding holes as they are removed from the head.
For extra security, I also stencil the valves themselves as is visible above.

Best, Aris

Aris, is that a piece of something wedged in between the valve guide and the head in that picture?
I'm sure you've inspected it thoroughly and it is just an optical anomaly.

Jeez, now you got me super-sensitive to inspection / cleanliness for beads.

Barry

Kool_Biker wrote:

P1070813.jpg

Hi Barry
This is just light reflected off oil which dribbled down there as I inserted a well oiled valve stem down the valve guide; always a good practice during the lapping process, keeps the guides happy. The super narrow field of view of the camera makes it difficult to see, but it is oil. Thanks though, this is appreciated and you can't be too careful!

Cleanliness. Ha!
One thing I have found during my well documented ordeal: You can't be too careful with this
Try the following; Take any part of a dismantled engine. Put it in your favorite degreaser, scrub it, what ever. Then clean it further with petrol, what ever, and then wipe it dry.
It should be clean. Right? ---- Wrong!
Hold the part with one hand and spray some brake cleaner (love the stuff!) on to it. Then observe in awe a streak(s) of fine dirt coming off and flowing down the part!!!

Oh, and while lapping the valves I could not avoid thinking that if anything, the lapping paste must be 10 times as aggressive as glass! So getting every spec out of my head is paramount!

Cheers, Aris

Aris:
I'm about to lap the valves in the head of the engine I'm building. I tested them with compressed air blown into each inlet and exhaust port. Squirt a little heavy oil around the valves you are checking. Lots of bubbles will appear around the seat if it does not seal well. This head was from a great running engine with 38,000 miles. I found 2 inlet valves leaking significantly and nearly every exhaust valve bubbled at least a bit. I did not check compression before teardown, but it ran fine. So lapping these in should be even better. I assume you found a trick to install the valve seals? If not, let me know.

What I've found is that the material you wipe parts down with will leave 'fuzz' that even brake cleaner will not completely remove. I guess paper toweling is the preferred materiaal as the paper fibers seem to dissolve somewhat, whereas cotton and the like will not. I confess to using both, and you will see fibrous material accumulate on the sump screen the first couple of changes. I do not know how it can be helped. But after a couple of oil changes all has been well with the ones I've done.

Dave

daves79x wrote:Aris:
I assume you found a trick to install the valve seals? If not, let me know.
Dave

Dave, Hi

Not there yet .. the forthcoming problem has crossed my mind, and in fact, I was going to ask you

As I have said before, I think, my head was 'professionally' refurbished during my previous rebuild, so I had not assembled it as such, never tried to assemble a seal before. And mine have all now suffered a cruel death and will be replaced with new ones ... Why is it hard, what's issue? I am sure we will find a solution

Cheers, Aris

daves79x wrote:Aris:
This head was from a great running engine with 38,000 miles. I found 2 inlet valves leaking significantly and nearly every exhaust valve bubbled at least a bit. I did not check compression before teardown, but it ran fine. Dave

I guess the reason could be that the combustion pressure pushes down the valve and helps it closing, whereas the compressed air in the inlet and exhaust ports wants to push the valve open.
Desmodromic valve trains can not positively close valves with pressure, so they use hairpin springs to push the valves against the seat.
Some race motors with desmodromic valve trains do not have closing springs and rely on the cylinder pressure to close the valves completely. It would mainly be an issue at idle and as idle is not that important in a race motor, they don't care.

daves79x wrote:Aris:
I tested them with compressed air blown into each inlet and exhaust port. Squirt a little heavy oil around the valves you are checking. Lots of bubbles will appear around the seat if it does not seal well. I found 2 inlet valves leaking significantly and nearly every exhaust valve bubbled at least a bit.

Dave

Dave, I am not sure how this works.
What's wrong with filling the head domes with petrol or paraffin, and looking for leakage 2, 3 or 5 minutes down the line? Seems easier to me
One question of course (important in my case) is do you put the springs on? Afraid, the answer is probably 'yes', to keep the valves down with some force.

Best, Aris