None of my used shims show any wear and they all measure the correct thickness so I don't think it's a problem.

Well, I've run across one or two that were 0.0005 out or so. The surfaces didn't show any degradation so I used them again. I am begining to think Chacal has a very valid point because hardening is not going to be very deep given the cost of the shims. I wish we could do some tests. Perhaps I ought to sacrifice one or two shims in the name of science. Is there a way to determine hardness across the cross sectional thickness if I cut the shim in half?

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I've swapped shims around (of course after measuring them) successfully for years with no ill effects. Has there been any reports of used shims causing problems with the old XJOwners shim pool? I haven't heard anything to date. Now I suspect they have been at it a while so if anything untoward had occured, we would have heard about it by now. Your thoughts?

Unless people re-measure their clearances after re-installing a used shim, they'll never know whether there is a "problem" or not. I would hazard a guess that many people do NOT re-measure. As far as any problems surfacing, remember: you CAN compensate for uneven valve clearance via butterfly shaft position adjustments during the "synch" process. But also remember: the "synch" process by its nature drags all other cylinders down in output to the level of the lowest (worst) performing cylinder.

It is for that reason that you want all the valves to be adjusted properly, and ideally, each to the same identical setting, even though Yamaha specifies a range of allowable clearances (the absolute number within the allowable range isn't an issue, you would just ideally like to have all the valves at the same setting within that range. Technically, to get the most cam lift (and therefore performance) out of the engine, you would want all the clearance to be set at the same amount AND that amount would be as close as is possible to the low end of the allowable range, meaning as minimal clearance as is possible).

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Well, I've run across one or two that were 0.0005 out or so. The surfaces didn't show any degradation so I used them again. I am begining to think Chacal has a very valid point because hardening is not going to be very deep given the cost of the shims. I wish we could do some tests. Perhaps I ought to sacrifice one or two shims in the name of science. Is there a way to determine hardness across the cross sectional thickness if I cut the shim in half?

Unless there were other types of problems/issues present, you will never see any surface degredation on a shim. A few microns is way past the ability of the human eye to resolve.

A shim that is off by .0005" is off by .0127mm (I assume that the .0005 measurement is in inches?). Valve shim thicknesses are expressed in millimeters, i.e. a 270 shim is 2.70mm in thickness, and shims come in .05mm increments. So a shim that varies by .0127mm from indicated IS within the range of shim increments, but also notice that it is fully 25% OUT of spec in relation to the incremental size difference (.0127 divided by .05). ALso note that the allowable range of valve shim CLEARANCES is even smaller: .04mm (as in: inlet clearance allowable range is .11mm - .15mm). A .0127mm deviation is almost a 33% deviation within the allowable range.

As far as determining the hardness of a material, there is a Rockwell hardness scale and process/tools for doing such measurements; large testing labs or high-end machine shops probably have such equipment. I would agree with you that a test of the depth of the hardening would reveal that the hardening process applied to the shims is literally "paper thin", if that much!

Look, you can swap used shims around and as long as you re-measure and are sure that the hardened surface treatment has not been breached (which I do NOT know how to check in any cost effective way), then you're fine. On the other hand, new shims are anywhere from $7 to $11 each, you're only going to need a few (hopefully!), and to me, the risk versus savings equation of re-using a worn part---one that is designed, by the way, to wear out and be replaced---just doesn't balance out.

That's why I don't re-use old shims. The factory agrees. Perhaps their engineers were ignorant, or perhaps they were so profit-driven that they were hoping to possibly squeeze an extra $20-30 out of each customer every 5-6,000 miles during the valve clearance adjustment proceess---AND, if you notice the mileage readings of most of these older XJ models, most are in the 15K-45K range AFTER 25 years!! Meaning an average of 1-2,000 miles per year. Meaning valve shim replacement every 4-5 years. Meaning squeezing $20-30 out a customer needlessly every 4-5 years. Meaning an average of $5 - 7 per year. And, meaning---in the "bigger picture" view---schlepping an extra $5 per customer, per year, on top of a, what, $200 service procedure?

Maybe that's what they had in mind. Maybe not. Everyone has to make the decision as to what they think is best given their own specific circumstances, needs, abilities. I'm providing and sharing the most accurate and honest information and analysis that is available to me, and which I consider to be accurate. Trust me, the markup on valve shims is NOT going to make me (or anyone else) wealthy, in any shape, fashion, or manner!

>Unless people re-measure their clearances after re-installing a used shim, >they'll never know whether there is a "problem" or not. I would hazard a >guess that many people do NOT re-measure.
Who wouldn't measure the clearances after putting in the new shims to make sure they got it right? I always do. Besides, all the other shims in there are used so I wouldn't want to throw everything off by mixing in some brand new ones.

I always re-check clearances after reinstalling shims. Maybe I'm obsessive, maybe thorough, i don't know.

The only wear I've noticed has been where the shim was installed upside down and the numbers have worn off. Correction - on a couple of shims there was a slight discolouration/whitening.

I have, however, checked the thickness of shims with a micrometer (albeit a cheap one). According to my (cheap) micrometer the thicknesses were not exactly as specified, but were the same at all points on the surface - ie no perceptible wear. I did this because some of the shims had no visible number and because I wondered if the hammering would cause any flattening.

At the risk of sounding lazy, I just use a go-no go way of checking clearances. In english: as the inlet clearance is .10-.15mm and exhaust .16-.20mm, if you can put a gauge .10 thick into the inlet gap, but not .15 (or for exhaust .15, but not .20) then it's ok. If the .15 sides easily, but not the .20 (pn the inlet), then one size larger shim is needed.

I check it again because it does seem that not all shim thicknesses are exactly made in .05mm increments - or maybe my gauges are not exact, I don't know. It may be that sometimes a clearance is at the point where it's on the border of sizes, so I have to agonise a bit. Anyway - that's why I check afterwards - to be honest, I thought everyone would - surely you check you've got it right while it's apart ??

The other point is that I obviously have shims from at least two different sources judging by the style of the numbers printed/etched on them - that may be another reason for any variation.

PS - my understanding is that these shims are stamped out of sheet the required thickness. My mind boggles at what could be hard enough to accurately and neatly punch a hole through steel as hard as this.

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I always re-check clearances after reinstalling shims. Maybe I'm obsessive, maybe thorough, i don't know.

Thorough. You play by the rules. You measure twice and cut once.

Your bike thanks you for your efforts!

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The only wear I've noticed has been where the shim was installed upside down and the numbers have worn off. Correction - on a couple of shims there was a slight discolouration/whitening.

Mmmmm....I do not believe that both sides of the shim are hardened.

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Anyway - that's why I check afterwards - to be honest, I thought everyone would - surely you check you've got it right while it's apart ??

Mmmmm......that's quite optimistic of you!

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PS - my understanding is that these shims are stamped out of sheet the required thickness. My mind boggles at what could be hard enough to accurately and neatly punch a hole through steel as hard as this.

I believe that the shims are punched first, ground smooth and sized, and then heat-treated to the appropriate hardness.........

You may well be right, I do know that once an engine has settled, there is very little variation in the shims needed unless something else is changed. If I have reground the valves during a top end rebuild, for example there will need to be new shims. What I'm saying is that I haven't noticed perceptible wear on shims (or camshafts, as I'm good on oil changes), despite muc higher mileages than some posters have talked about - 75,000 on the XJ750 and maybe 180,000 on an XJ550 (with engine rplacements and rebuilds over the past 18 years) [That's total mileageincluding previous owners] plus fewer miles on another 550 and 650.

Heat treatment after being stamped out is possible and may mean it's the same thickness throughout (dependant on rate of cooling, heat and metal composition).

I was able to get all the shims but one that I needed for the 1100 free from the xs11.com groups free shim exchange program and only had to pay for postage. The last one I got from the local bike shop for $8.00 exchange.

By the way, LtDave is hilarious.

But now that the winter FINALLY gave up, I think a regular shim pool would do just fine. My xj is much less cranky too.

But, concerning carb clinics, this can be a problem, since nobody would know what sizes he needed until the day of, and then it's kind of too late (at least if it's supposed to be a 1-weekend thing). Is there any way people could order the most common replacement sizes and maybe send back (or send around) the ones they didn't need? Something like that, anyway.

chacal wrote:

On the other hand, new shims are anywhere from $7 to $11 each, you're only going to need a few (hopefully!), and to me, the risk versus savings equation of re-using a worn part---one that is designed, by the way, to wear out and be replaced---just doesn't balance out. That's why I don't re-use old shims. The factory agrees.

So, these are designed to wear out. At what milage did the factory engineers tell us to chunk them all regardless of clearance. If a shim has been in there for 30k miles is it time for it to go? I've read here many places that as time goes on, there is less need for change since the actual wear parts (valve seats) wear less. Are you saying that the shims are the wear part and if so, how often should all of them be changed?

The factory said not to...

so I don't re-use old shims period. Maybe it's being overly cautious, I don't frankly know. I DO know that the cost to repair damage caused by a spit shim is many times the cost of a new one; I regularly run my XJs to 8K or 9K... I'm simply not taking any chances.

Okay Fitz, this is my last set of questions on this, then I'll stop and let everyone make thier own decision.

1) Where does the factory say not to reuse shims?

2) If the shims being "worn" is an issue, what is the milage limit for a shim? (its not when its out of spec, because that wear is not on the shim, but elsewhere).

3) If I check the clearance and its good, but pop the shim out to read it to make a shim map for future reference and put it back in(or just to find out what I need to fix an out of spec one) how is that different from moving it from one valve to another in the same engine? In other words, once a shim is out of a bucket should it be replaced and if not, why does it matter where I put it back? (yes, I know it chages the clearance on that valve, but other than that. Why is it more likely to be thrown by a different valve than it came out of?)

4) If wear on the shim were an issue to the engineers at Yamaha, wouldn't they have a replacement interval for all shims as opposed to only those whose valves have set enough to be out of spec?

I know its my bike to do with what I want and same for you and everyone else out there.

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1) Where does the factory say not to reuse shims?

They say to replace shims with "new" pads, i.e. "Install the new pad with the number down." The word "new" can be interpreted either as "new", meaning just that (brand new) or it can be interpreted as meaning "another pad of the same size; "new" as meaning "different from what was originally int here").

In almost all other cases, the word "new" in the service manuals refers to a new part, not a replacement used part.

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2) If the shims being "worn" is an issue, what is the milage limit for a shim? (its not when its out of spec, because that wear is not on the shim, but elsewhere).

The wear could be on the shim, the cam lobe, the valve seat, or a combination of all three. Some service manuals specifically states to measure any used shims with a micrometer to verify that the stamped size is the actual size due to wear; otherwise, your calculations will be off.

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3) If I check the clearance and its good, but pop the shim out to read it to make a shim map for future reference and put it back in(or just to find out what I need to fix an out of spec one) how is that different from moving it from one valve to another in the same engine? In other words, once a shim is out of a bucket should it be replaced and if not, why does it matter where I put it back? (yes, I know it chages the clearance on that valve, but other than that. Why is it more likely to be thrown by a different valve than it came out of?)

Shims develop wear patterns in conjunction with their specific cam lobes.

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4) If wear on the shim were an issue to the engineers at Yamaha, wouldn't they have a replacement interval for all shims as opposed to only those whose valves have set enough to be out of spec?

There are no replacement intervals given for many wear items; i.e. brake pads, engine bearings, etc. Why would they specify replacement intervals (miles or time) for items that may not be out of specification?

While you are hot on the subect, Len, when I re-shimmed this 900 so I could get reliable comp' readings, the new shims all gave a tighter readings than they should? do they have to bed in? '2' when i put this motor back together I will be reusing the original shims to get me started,no? none will be ok as the valves have been lapped ect, so I check them all & buy 8 new, now will these have to be bedded in & replaced again, or is there a fomula whereby you make some allowance?

Hey Wiz, well, I'm not sure that I understand the question(s)? You re-shimmed the engine in order to take compression readings (loosen up the clearances, correct?) but you state that the new shims all gace tighter readings "than they should"? I guess I'm not sure what you mean when you say "should"...................."should" as compared to what other readings?

As far as when you get the valve seats ground, yes that will of course change clearances, you will re-measure clearances and calculate what is needed and then order the appropriate sized new shims as needed.

Obviously, with a "fresh" motor, you can expect some level of clearance changes to occur as the parts all bed in and experience initial wear, etc. since the valve clearances tend to shrink over time as "wear" (or "bedding in") occurs, then it would probably be wise to begin with using the largest possible clearances possible, in other words, if there are any "borderline" clearances to the tight side, go up one valve shim size even if that means going slightly out-of-spec on the LOOSE side, as that "looseness" will go away fairly rapidly, and thus you may not need to exchange shims.

Yamaha recommends that an intial valve clearance check be performed during new engine break-in after 3K miles (5K km) and then after every 5K miles after that, although I would tend to suspect that the majority of the new/fresh engine bedding in of parts occurs much more quickly than that.