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Discussion Starter · #1 · (Edited)
For those high mile riders reading this, do your valves tend to tighten or loosen over time? I'm shimming right now and on some valves have to decide between the low or high end of the spec.

Those newer to the wrenching may wrongly believe that valves always tighten over time. Whether the cam lobe to bucket gap increases or decreases over time is a function of cam lobe wear (widens gap) vs valve seat recession (shortens gap). Some engines are designed so these opposing factors cancel one another out and gaps are held relatively constant. Another factor to consider is the smaller the gap the greater the valve lift and theoretically greater flow and power. Too small a gap, especially on the exhaust side, and heat will buildup and in the worst case scenario, damage a valve.
 

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I love your spirit and honesty. I'm being critical of this job, in general, not you as a person. As a person, you are one of a kind and I appreciate you....with that said. You have the theory correct, but perfect execution is way more important.

The truth is, they don't don't do much of anything, long term. Very much like clutch plates in that regard. The amount of allowable wear is almost zero. If you did have to change to a shim 5 or six steps different than what you have, your fix is temporary. Most of the reason these are checked is due to emissions reasons rather than mechanical. Kawasaki certifies the engine will be emissions compliant with X valve lift,y cam duration,and z overlap. When the shim size is off, it changes these specs, slightly and they want to make sure you are within tolerance.

On the first inspection, it is not unusual to find some that are on the tighter end of the scale. Maybe even slightly under scale.

Loose valves are usually a measuring error. If you had to make a rule, you would say that they tighten over time. I'm talking about Japanese motorcycle heads. Not Italy. Not china. Not German.

Typically these Japanese heads, with stainless steel valves stay where you set them until something truly does wear out.

If you have a head where the valves are moving, tightening up, it doesn't matter what you set them to. The head will need a rebuild if the clearances don't stay stable.

The measuring range we are allowed to set these valves in amounts to a thick "almost nothing" to a thin "almost nothing." In range is as good as it gets. You won't accomplish anything by playing around with large or small sections of this range.

You also see a lot of people ruin excellent motors when they try to adjust the valve shims. I could show you a stack of damaged zx14, Concours 14 or ninja 1000 motors where something went wrong as the owner attempted to re-shim a slightly tight valve that would have never been an issue.

Please don't take my word for it. Search and learn, yourself and see how many people are lucky to have caught this "tight valve just in time" at 16,000...... 36,000...….48,000mi. Always just in time. Always slightly tight.

Most people who damage engines are so obsessed about the exact shim spec that the basics are missed or glossed over. Now the fun begins.

Ironically, a burned valve that ran at zero clearance brings a person right where you are to needing a new head or some head work.

Unless a person is 100% able to do this job, without mistakes, the risk vs reward factor doesn't work out.
 

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Discussion Starter · #3 ·
I love your spirit and honesty. I'm being critical of this job, in general, not you as a person. As a person, you are one of a kind and I appreciate you....with that said. You have the theory correct, but perfect execution is way more important.

The truth is, they don't don't do much of anything, long term. Very much like clutch plates in that regard. The amount of allowable wear is almost zero. If you did have to change to a shim 5 or six steps different than what you have, your fix is temporary. Most of the reason these are checked is due to emissions reasons rather than mechanical. Kawasaki certifies the engine will be emissions compliant with X valve lift,y cam duration,and z overlap. When the shim size is off, it changes these specs, slightly and they want to make sure you are within tolerance.

On the first inspection, it is not unusual to find some that are on the tighter end of the scale. Maybe even slightly under scale.

Loose valves are usually a measuring error. If you had to make a rule, you would say that they tighten over time. I'm talking about Japanese motorcycle heads. Not Italy. Not china. Not German.

Typically these Japanese heads, with stainless steel valves stay where you set them until something truly does wear out.

If you have a head where the valves are moving, tightening up, it doesn't matter what you set them to. The head will need a rebuild if the clearances don't stay stable.

The measuring range we are allowed to set these valves in amounts to a thick "almost nothing" to a thin "almost nothing." In range is as good as it gets. You won't accomplish anything by playing around with large or small sections of this range.

You also see a lot of people ruin excellent motors when they try to adjust the valve shims. I could show you a stack of damaged zx14, Concours 14 or ninja 1000 motors where something went wrong as the owner attempted to re-shim a slightly tight valve that would have never been an issue.

Please don't take my word for it. Search and learn, yourself and see how many people are lucky to have caught this "tight valve just in time" at 16,000...... 36,000...….48,000mi. Always just in time. Always slightly tight.

Most people who damage engines are so obsessed about the exact shim spec that the basics are missed or glossed over. Now the fun begins.

Ironically, a burned valve that ran at zero clearance brings a person right where you are to needing a new head or some head work.

Unless a person is 100% able to do this job, without mistakes, the risk vs reward factor doesn't work out.
I would agree with just about everything in your post. I've read of ZX14 owners complaining about the difficulty and even the risk of shimming. Personally, I like to get everything perfect then enjoy years of riding and redlining the engine as the spirit moves with no worries. The ability to sleep like a baby to me is more important than the hassle involved with a shim job. In this particular instance I'm installing a replacement head that came without shims. I'm forced to measure and pick suitable shims. For example, when the spec is .15 - .21 and I'm sitting at .20 do I stick or go down to .15? Answer depends on whether gap widens or decreases over time for this particular engine. Depending on my choice, I'm either moving steadily towards the middle of the spec or moving further out of spec as the miles accumulate.
 

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In this specific context, on this head, you would shoot for .20 as these valves tighten, over times if they even move at all.

We don't know where the starting point was other than we hope Kawasaki set them with range. The valve may have started life at .15 and might be at .15 after 100,000 miles have passed.

With that said, if you were at.15, leave them alone. You don't accomplish anything by shimming valves that have stayed in range.

I'm not sure what the temp is in your shop. If you are trying to work and mess around in that small range, the temperature has to be steady and your feeler gauges need to be expensive, high quality pieces.
 

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The valve clearance threads are always interesting because of everyone's experience and to see if there is a general trend. My recent experience with valve clearance checks isn't so recent anymore as my former C14 has been gone for over five years. In the 53k miles with it I did three valve clearance checks and never made adjustments. Though, I have read where guys have made adjustments with similar measurements because they want to be in the middle of the range. It's a lot of additional work.

Shim changes were easy with the old shim on top of the bucket engines from Kawasaki and Yamaha.

So I went back into my C14 maintenance files and found the 30k and 50k valve clearance check measurements. (Not sure where the 16k adjustment notes are at--those were hand-written and probably in a box with the manual.) Anyway, below you can see how over 20k miles there was a very slight migration to getting tighter. But, they are stable. Another check would have been interesting to see how this trend would have continued.

This is going to drive me batty because I feel like one or more valves actually loosened from the 16-30k check.

Anyway, here are some snipets if anyone is interested. The measurements do collaborate what's been mentioned already.

30k miles:
Font Rectangle Line Parallel Pattern


50k miles:
Font Line Rectangle Parallel Pattern
 

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I would love to see how they do this on the assembly line. Do you suppose they assemble this twice? Build one as a baseline, then substitute the correct shims, if needed?
 

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Good question. I'd suspect there is much awareness of the valve seat machining, cam line boring, and cam dimensions there is a trend that a standard set of shims put the clearance in spec. Then, as those guys with the colored QA markers check final clearance they would have enough experience to see slow changes to valve clearance as cutters/tools wear down. A change of a cutter/tool and the clearances are back in trend.

But now, a hand-built engine like a Ducati, Buell, or whatever, those guys are checking and adjusting clearances for sure.

Just my speculation.
 

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It always surprised me to see that there wasn't really a common, go to shim in the original head. They are within a range, but not specific.

I wonder if they have a way to measure before the cams go in?
 

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I remember reading about people who would swap their zrx 1100 cams for the zx11 cam. Apparently it gave a big HP increase. Sometimes the zx11 cam was new, or used...it didn't

Most of the time the cam dropped right in and did not require a valve shim change. That helped me realize just how precision oriented they are when they build these engines.

I had 79 xs11 that was Indigo blue color. I never adjusted it's valves.

I did screw up a kz650 valve adjust when I was 14. I missed the part where you line up the timing marks. No idea how, but I did. I think that is step 1 in the process? Proving once again that you can't fix dumb.
 

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I have not read every post as I’m in a hurry to get out of the house ( so this may have been answered already) but you should shim to the "loose" end of the spec as over time the valves tighten due to valve stem stretch and valves wearing into their seats.
If it were only cam wear, the opposite would be true.

As your engine gets more miles on it, your valves and stems find their happy place and you can go longer between adjustments. But if you keep your bike long enough with tons of miles, you will eventually not be able to find shims thin enough to get the proper spec as the stems have stretched to much and/or your valves have seated too deep… notice you always need thinner shims as the miles pile up.
In this case you need to pull the head and have your valve stems shortened. There’s a machine for that.
Or just buy a low mile head. Cheaper.
 
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