Removing Cams - Question

[jetmechmarty]

IAW the FSM, what you oil is the threads. Just a couple drops should do it.

Does the compression test fail?

[Radioguylogs]

Compression passes when measured cold., It's 150 across the board, except #3 was 10 PSI lower than the others until I retightened the head nuts. Details are in the earlier posts of this thread.

One thing that is bothering me, is that I replaced the head gasket on an XS750 twice, using the same torque wrench, and the same techniques, and everything was fine. I did use Yamaha head gaskets.

Right now my plan is to remove the head, inspect the head gasket. Replace it with an NOS Yamaha gasket. Have a second torque wrench on hand. Consensus so far is to oil the stud threads only, and not the nut flange.

[Radioguylogs]

Removed the head.

No smoking gun. Everything looked perfect, torques felt normal taking everything apart.

I had hoped to see some carbon trails on/around the head gasket so I would know for sure what the problem was. Gasket looks like new. Aluminum surfaces are squeaky clean.

I did observe the head studs look totally dry, so I must have neglected to put a little oil on them. Geez, could that be the cause of all this trouble?

[Schming]

I tightened the head bolts (nuts) and started it today.

At first, it sounded normal except #2 cylinder didn't seem to firing, because that vacuum gauge was near 0 PSI. (That plug looks very clean compared to the others.)

As I tried to adjust #2 sync to see if it was just set too low, the awful sound came back.

It went Erk-Erk-Erk-Errrrrrrrrrrrrrrrrrrrr. It is loud and sounds like something is terribly wrong.

I drained the oil and I didn't see any metal flakes, although I haven't poured out the pan to see what might have settled.

I did notice that as the most of the oil had come out, I began to see a lot of foam in the oil. In fact it seemed like the bubbles sometimes came up from the oil. I wonder if it is exhaust residue.

Therefore, I am beginning to conclude the head gasket installation is NG.

Hi Mike, JAT Do you think this particular sound may have something to do with the starter clutch ?

[Radioguylogs]

Hi Mike, JAT Do you think this particular sound may have something to do with the starter clutch ?

I'm not leaving any stones unturned, so I should think about that idea. I have done a fair amount of cranking to perform compression testing.

I'm also wondering if it is possible for a new valve seal to pop off. Seems like there would be a lot of smoke if it did. However, I didn't let it run for more than a few seconds. I'll take a peek under the shim buckets.

[bikerphil]

Just a thought, the squeal may be one or more of the cam caps not getting oil. Dry metal to metal turning could possibly make a noise you're describing.

[Radioguylogs]

Just a thought, the squeal may be one or more of the cam caps getting oil. Dry metal to metal turning could possibly make a noise you're describing.

Thank you for your suggestions. I know you have a lot of experience with this type of operation.

There are rub marks on few of the cam journal surfaces, but they were all loaded with fresh clean oil. I remember seeing the rub marks when I took it apart the first time. They are not deep scratches, just areas that look a little more shiny. Maybe I can post a picture tomorrow.

Meanwhile, tonight I removed each valve and inspected. Each valve moves smoothly, and seats nicely. Each new valve seal is sitting snugly in place. Everything look perfect in there.

[bikerphil]

Another thing that comes to mind, one time I had an intake boot leaking at the head and it was making a chirping sound, may have sounded like squeaking.

[Radioguylogs]

Another thing that comes to mind, one time I had an intake boot leaking at the head and it was making a chirping sound, may have sounded like squeaking.

Not sure how to test for it before installation, other than a visual check. Maybe try blowing into each one with the valve closed.

After installation, I can be on the lookout for this if the problem comes back.

[bikerphil]

Yep, I removed each boot and applied a thin layer of RTV to resolve.

[Radioguylogs]

Maybe try blowing into each one with the valve closed.

I tried putting my finger over the vacuum ports, and blew into the intake boots. Each of them was letting out air somewhere inside the head. Rather strange, but they were all the same, so I dunno what that means.

Maybe the valve seals can let the air pass outward.