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Old 08-22-2013, 07:23 AM   #1
Cpt. Ron OP
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Valve Lash after Top End Clean Up

I tried asking this in the Garage forum and got nothing.....

So I'm in the process of putting my 950 back together. I took the top end and jugs off to fix a leaking base gasket. While the heads were off, I decided to clean up the valves and seats using some valve grinding compound. Upon reassembly, I double checked the valve lash was reasonable with the shims that I had in the motor before tear down. A short run up to verify that everything worked and then one more check of the valve lash. Two of the exhausts had significant increases in the lash measurement. According to my log, the last measured gap was .254mm, but now one is .406mm and .356mm.
All of the parts in the valve train went back into their original position, nothing got mixed up.

Now, I'm not surprised to see a change in the lash after doing the work that I did. But I figured the lash would decrease since I removed carbon as well as a little material from the valve and seat faces. Am I worrying about nothing? Can anyone explain the change?
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Old 08-22-2013, 07:30 AM   #2
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Sounds like a trick question cause it doesn't make sense.
Are you sure there is no human error in measuring?
Did you try giving the engine a few more turns after those measurements?Just to make sure.
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Old 08-22-2013, 09:48 AM   #3
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Yeah, it doesn't make sense, hence me posting here with my hat in hand.....

Yeah, I'm going to double-check the measurement. But to back up what I measured, I did run the bike and there was certainly excess noise due to the large gap on the exhaust valve.

So, what can it be?

Measurement error? Most likely, I am human. But I find it hard to squeeze in too-tight feeler gauges.
Took too much material off of the stem of the valve? Not likely, since I didn't touch that end.
Added too much hard facing on the valve? Doubtful, I can't weld like that and didn't try anyway....
Some dust/debris between the valve face and seat? I don't think so, especially since I ran the motor already.
Not enough oil between the bucket/shim/valve? Strange, since the other valves didn't change nearly as much.
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Old 08-22-2013, 03:40 PM   #4
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Have you mic'ed the original and replaced base gaskets? I wish I had more to offer but that's all I can think of.
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Old 08-22-2013, 03:46 PM   #5
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Being that it's not a pushrod motor, the base gaskets won't affect the valve lash. The cam chain tensioner will handle any difference in the base gasket thickness.
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Old 08-22-2013, 03:59 PM   #6
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Of course. I wasn't thinking. I'll stay tuned for the solution!

Quote:
Originally Posted by Cpt. Ron View Post
Being that it's not a pushrod motor, the base gaskets won't affect the valve lash. The cam chain tensioner will handle any difference in the base gasket thickness.
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Old 08-22-2013, 05:56 PM   #7
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Last try: it doesn't seem crazy that your valve lapping compound could have removed the .15mm. You might want to try the same procedure on some scrap and measure the difference.

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Old 08-22-2013, 06:41 PM   #8
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Assuming everything is assembled correctly, its an X file case.
stating the obvious, re-check and set to the correct gap.
and dont run it over 9200 RPM.
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Old 08-22-2013, 07:46 PM   #9
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Quote:
Originally Posted by jwalters View Post
Last try: it doesn't seem crazy that your valve lapping compound could have removed the .15mm. You might want to try the same procedure on some scrap and measure the difference.

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I agree with the first part; yes the compound would/will remove material. But that would move the valve further into the cylinder head/valve face. Which would push the stem further up into the shim/bucket/cam assembly. Thus, reducing the clearance between the top of the bucket and the camshaft.

But my clearance increased......
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Old 08-23-2013, 12:27 AM   #10
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Just lapping the valves in shouldn't cause that much of a difference, nor should there be that much wear and anyway it would be there before you did the work anyway! Just a thought, you haven't put the shims back in the wrong position? One other thought, you aren't a tooth out on the cam position are you?
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Old 08-23-2013, 07:36 AM   #11
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When it came apart, every valve and associated pieces were put in individual zip-lock bags and labeled with their position. Upon reassembly (and the ensuing quandary....), I verified the shims to my notes from previous checks and adjustments. I believe having the cam a tooth off could only make the lash tighter, not looser.

I'll be verifying the whole the again today/tonight. I may end up using locally sourced 9.8mm shims if my shipment of HD shims doesn't come today.
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Old 08-23-2013, 07:50 AM   #12
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Cam bridge bolts loose?
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Old 08-24-2013, 09:21 AM   #13
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If your feeler gauges are not bent at the end and you check the clearance with one feeler gauge, you will get a smaller figure than with two because the feeler gauges need to flex to get into the gap and the single gauge flexes less than 2.

So if you used just one gauge in the past, the reading with 2 gauges will appear looser, but its actually operator error ;)
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Old 08-24-2013, 09:40 AM   #14
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Quote:
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If your feeler gauges are not bent at the end and you check the clearance with one feeler gauge, you will get a smaller figure than with two because the feeler gauges need to flex to get into the gap and the single gauge flexes less than 2.

So if you used just one gauge in the past, the reading with 2 gauges will appear looser, but its actually operator error ;)
I'm afraid I don't follow what you're saying. But I've been measuring this machine with the same set of feeler gauges (with bent tips), so any user error should be repeated. I only use one feeler gauge at a time, I don't stack them.

Lying awake in bed early this morning, I had an epiphany. I wonder if the valve got damaged or bent or something like that. If it doesn't close all the way, that could cause my problem. So, I'm on a quest to find a leak down tester....with a 10mm adapter. No one local seems to stock that. Crap.
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Old 08-24-2013, 10:37 AM   #15
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Quote:
Originally Posted by Cpt. Ron View Post

I wonder if the valve got damaged or bent or something like that.
What would be the reason for that ? was this cylinder (i am assuming that both those valves are of the same cylinder) off timing at any point?
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