Valve clearances again

I feel like this topic has been talked to death on this site and I have tried searching for my answers but have not found what I really wanted to know.

First a quick question. I pulled all the shims out to check their numbers so I could have them on record. One the marking was rubbed off. I measured it at 2.67mm I'm assuming that is a Y270 that has just worn down? That was the #2 intake shim. Should I get a 265 to put that back at the high end of the spec?

On to the next question Here is my chart (metric feelers were used)

#1 #2 #3 #4
Ex: .23 .15 .15 .20

In: .20 .13 .15 .20


I'm not sure if my measurements were accurate. Intake and Exhaust on #1 are loose and so is Intake on #4. Is it possible that I measured wrong? Could I have put the cam shaft in a position where the gap would be greater than if it were in the correct position for measurement? Should I go ahead and go up a shim to get them in spec?

The other thing that is getting me is I have had this bike for several years and put at least 10,000 on it if not 15,000 on it and I have never touched the valves. Shouldn't they all at least be on the tight side? Or did one of the POs really screw up valve shims?

 

Are you sure about your measurements? Not of the clearances but of the shims?

The shim numbers ARE their measurements; a 265 is 2.65MM thick.
If you found a 1.67MM thick shim it's likely not from a Yamaha as they only ever wear by a few thou if that; the valves pound into the head more than the shims wear. The smallest shim available for our bikes is a 200, or 2.00MM thick.

Another possibility is that you might have a warped valve or two that aren't closing fully; those would read "loose." Did you do a compression check?

There's no "more clearance" zone, the round part (heel) of the cam is where the measurement is done, directly opposite (180* from) the lobe.

They should be shimmed to spec; but the extreme looseness of a couple of them along with the "neglected mileage" makes me think there might be more afoot. You don't want to "correctly shim" a valve that isn't closing fully, you wouldn't be. I would do a compression test. (Set the valve cover back on, if you spin the motor with it off it makes a terrible mess. Honest.) If you come up with a couple of pots that are horribly low (like #1 or #4) then you should probably pull the head and investigate those valves. If the compression check results are fine, then shim away, and assume someone before you used gawd-knows-what for shims.

**QUICK EDIT: The Haynes manual incorrectly specifies .16mm-.20mm for both intake and exhaust. (The specs are really the same as all the other XJs, 11-15 and 16-20.) Maybe a PO shimmed to the incorrect spec. It doesn't explain a 1.67mm shim, but it also would explain some of the other findings. Do that compression test.**

 

I'm absolutely positive on the measurements but I'm not so sure on my ability to type them into a computer. That would be 2.67 not 1.67 I'll go correct that in my previous points.

I tried doing a compression test but I was never able to fit the tester that I was using in. These bikes use 14mm plugs right? I certainly hope that isn't the case. The bike has actually be running quite well. I'll borrow a compression tester again and give it another shot.

Thanks for the help.

 

Yep, 14mm plugs. A 2.67mm shim would have to have been a 270 quite possibly someone ground it down. Either that or your caliper had .02mm of crud on it, and it's a 265. I went out and measured the most worn-out shim I could find, a 260 and it still measures 2.60mm.

Definitely do a compression test; if it comes out OK then you know it was simply mis-shimmed. #3 and #4 are "expected" results, either ok or slightly tight.

Keep us posted.

 

Fitz is right about

but there is a lot of less clearance zone, check that 180 twice

 

I have a same problem, one of my shims have the number almost completely worn out, looks like - 2X0 - X assuming to be a 5, 6, 7, 8, 9 etc.
the other shims go from 250-265, can i use calipers to measure this shim and try fitting another measured one throught the calipers, from what i have been reading here, is that the shims do not normally wear down..... so in theory i could use the others as caliper guides unless the unmarked shim is less than 250 and higher than 265.

 

You sure can. You are correct in that even when they wear, it's barely measurable. Measuring them is the only real way to determine what they were anyway.

 

Finally got my valve cover all cleaned up and re painted I'll be putting it back on to do the compression test this weekend. Since its a 650 I have the little camshaft end plugs. I got replacements from Chacal and was wondering if I should use the gasket sealer to seal them to the head much like Fitz suggests to do with the valve cover gasket to to valve cover. Any thoughts?

 

Ok I finally got my compression test done. And here are the results

#1 #2 #3 #4
100 110 75 115


So something seems to be going wrong. Here is what is kind of weird though. 1 the bike has been running fine other than taking some time to warm up. It pulls strong (hit 100mph the other day). Could I be doing that if my compression was off that much?

The other odd thing was I decided to try a wet compression test. I put a little oil in the cylinders and retested and every cylinder easily went off the chart (over 250psi).

Comments? I'm confused and worried that I will need to pull the head off.

 

So I did another compression test tonight. This time I actually warmed up the engine (what a novel idea, I can't believe I didn't do that the first time around). Compression this time was

#1 #2 #3 #4
135 125 125 145

So Still low 2 and 3 and at the bottom of acceptable on 1. I would love to put new rings in and get it closer to 156psi but I don't have the time or the money. Right now I am just concerned about my valves.

Since my compression is OK and since the compression shot up one the wet test is it safe to assume that my valves are ok? I would like to just get the valves in spec and maybe to a quick carb sync and just keep it on the road for another 2 or 3 seasons. My kids will be older and hopefully I will have more time and money to dedicate to the bike. Thoughts?

 

Those are not "bad" results. Not great, but not horrible. The actual reading (which can vary greatly from gauge to gauge) is not as important as any extreme differences would be. You do have some cause for concern there; but I would adjust the valves and check it again. You might find that 2 and 3 come up a bit... I think you put too much oil in for your "wet" test I wouldn't keep that result in the equation.

Adjust the valves, check compression again, and then get it sync'ed up. You'll get some more miles out of it.

 

Thanks Fitz That is exactly what I wanted to hear.