Possible material in valve seat, how to remove

[Guest]

I have the head of my off-brand bike on my workbench. It is an 8 valve shim under bucket, similar to a GS shim over bucket engine. A few weeks ago I was working on it with the cams mounted, and it was sitting on a towel. I had been rotating the cams, and noticed part of the towel had caught under a couple of valves (I don't remember which ones). Silly me, I pulled the towel out with the valves closed. Now I am attempting to adjust the valves and find that two of them have unreal clearances that can't be adjusted by shims because the clearance is too large. I suspect that particles of that towel (long since banished from the workbench) remain under the vavle seats. I have tried opening the valves and wiping them with a paper towel, with no improvement.
All valves used to be close enough the be adjusted by shims, so this is a new development.
If my theory is correct and there are still particles there how can I remove them? The clearances measure 0.020" - 0.025" (twenty to twenty five thousandths of an inch) with a shim installed.
Thanks in advance.

[hampshirehog]

If you've got a compressor how about opening the valves and trying blasting some air through there? Tiny bits of towel won't do any damage in the combustion chamber.

[Steve]

Well, the material got in there when you were rotating the cams and had the valves open.

How about just rotating the cams to open the valves, then blowing out the port with some compressed air?

.

[koolaid_kid]

I have an air compressor, I'll give it a shot. Double entendre intended.
I know the carbon-based material won't harm the engine, but it prevents me from adjusting the valve prior to installing the head.

[Nessism]

I'd pull the valves out of the head and clean out any debris properly. I trust you have a valve spring compressor and have replaced the valve stem seals while the head is on the bench.

[koolaid_kid]

You are partially correct. The valve stem seals have been replaced. Unfortunately, I do not have a valve spring compressor. And I no longer have access to the one I used originally.

[koolaid_kid]

Well crud

Took it out the garage and tried to blow the debris out with the air compressor. No change. Took some declorinated brake cleaner and tried cleaning it with that. No change.
Any more ideas are most welcome.
Bwringer may have a valve spring compressor, but he is out of town this weekend.

[bwringer]

Took it out the garage and tried to blow the debris out with the air compressor. No change. Took some declorinated brake cleaner and tried cleaning it with that. No change.
Any more ideas are most welcome.
Bwringer may have a valve spring compressor, but he is out of town this weekend.

PM sent...

[Nessism]

Lots of people use a large C-clamp and piece of PVC as a valve spring compressor. Got a Harbor Freight in your area?

[koolaid_kid]

Went over to bwringer's and used his. Discovered an interesting thing: the valve is "sticky" when inserted the last few millimeters. I pulled it, cleaned it, reinserted it, had to tap it down the last bit. When I rotate the cam, it does not reseat itself completely, but I can tap on the valve and it will drop back down all the way. Hmmmm.
History of head:
This was in a running bike that I chose to rebuild. I pulled the valves, decarboned them completely with many hours of wire-brushing, lapped the valves, replaced the seals, and reinstalled the valves. The cams have been installed and removed several times. These valves chose to stick only yesterday (2 are sticking, I expect the others to start). What do I need to do? The valve I worked on, I lubed it all up and down with motor oil, I lubed the seal with oil, and it still sticks. They can't be bent, that would be almost impossible since they worked fine on the bench until yesterday. And they were fine when I was lapping them, which was an all-day task.
Any suggestions are gladly welcomed.

[Nessism]

Did you run a bottle brush down the valve guides to make sure there is no debris down inside? Could be some rust forming in the guide too. Best to be very careful to find the cause of this issue now.

[koolaid_kid]

Ed, I couldn't agree more that it needs to be resolved now. Hence the thread.
Since the head has always been inside my climate controlled home, the valves have always been in the guides, and the valve stems themselves appear perfect, rust is possible but highly improbable. The valve stem slides down into the guide fine until just the last few millimeters. It was quite odd.
On the plus side, I am going to strip the head down again, clean, paint and bake the critter.

[koolaid_kid]

Continued musings

Continuing along Ed's excellent line of thought, what if particulates got on the valve stems? I thoroughly lubed the stem yesterday, so lubrication alone could be ruled out. What could I polish the valve stem with to see if it loosened up slightly? I have some 2000 grit emery paper. It's only for the very last bit of the stem, perhaps the valve had been held open with the cam for some time? The cams had been removed for quite some time while the sprockets were being slotted, but I guess anything is possible...

[Nessism]

You might want to get a micrometer and measure the valve stems. Did you wire wheel the valve stems when you cleaned the valves?

The valve should not bind in the guide at all. Typically with used parts the valve wallows around in the guide due to excessive clearance, so your story is very strange indeed.

My guess is debris in the guide, guide rust, or valve damage. You will know more once the valves are out of the head.

Oh, and don't bother baking paint on a cylinder head. The first time you run the engine the paint will bake by itself.

[gs road racer]

I have the head of my off-brand bike on my workbench. It is an 8 valve shim under bucket, similar to a GS shim over bucket engine. A few weeks ago I was working on it with the cams mounted, and it was sitting on a towel. I had been rotating the cams, and noticed part of the towel had caught under a couple of valves (I don't remember which ones). Silly me, I pulled the towel out with the valves closed. Now I am attempting to adjust the valves and find that two of them have unreal clearances that can't be adjusted by shims because the clearance is too large. I suspect that particles of that towel (long since banished from the workbench) remain under the valve seats. I have tried opening the valves and wiping them with a paper towel, with no improvement.
All valves used to be close enough the be adjusted by shims, so this is a new development.
If my theory is correct and there are still particles there how can I remove them? The clearances measure 0.020" - 0.025" (twenty to twenty five thousandths of an inch) with a shim installed.
Thanks in advance.

OK I have been following this thread and thought it time to go back to the beginning.Something didn't jive, the picture I have in mind now is that the head is sitting flat a bench with a towel while you rotate the cams to check clearances.How did you rotate the cams? You rotated the cams with the weight of the head and pressure applied from your working is a better visual image coming into view? Those valves would have extended far below the head gasket surface. The head was off to rebuild a running motor that you chose to take apart.

I believe you have bent some valves (possibly most of them)...do you have any way to check run out on them? A quick couple of ways is to rotate them in the guide even a small bend should be noticeable.Or take a piece of 4x4 wood and layout enough holes in a line drill to little bigger then stem size (drill press required to make them all perpendicular and same depth) sight along the tops with them in the wood . Bends should be readily apparent and you now have a stand that can be used for the valves.Soft wood is great for this no damage to the stems like a metal stand might do.If you're going to do what you did in the manner which you did it , either a stand is required to hold the head off the bench or use the cylinder block to accomplish this with the old gasket or something to prevent damage to the surfaces.The guides are probably fine but should be checked as well.Time to take it apart to assess the problem.You're not the first or will be the last to do that kind of damage.

As with a lot of posts on here the more information even seemingly trivial may help solve problems. It's often hard to imagine what happened...the picture gets clearer with more information. Always go back to before the problem started.A description of your method (all of the steps taken) at the first could help troubleshoot.