Valve Clearance Shim Grinding

I would like to grind a few thousandths off of the valve clearance shims in my bike to compensate for tight clearances. Does anyone know if these shims are through hardened or just case hardened?

 

I believe they are case hardened and cannot be ground down. Member Hogfiddles runs a shim pool and all you do is swap your shims for postage cost.

 

grinding shims is something you don't want to do

 

Polock..sounds like you have a shim to grind...lol...sorry...couldn't help it...must be the lunar eclipse or something...

 

The "system" is set up so that you SWAP OUT shims for thinner ones.

They come in .05mm incremental sizes, and the spec range is similar such that one size shim, and only one size shim, will put any given valve within spec. If you have say, an intake valve too tight at .10mm, then a one-size smaller shim puts you in spec at .15mm, and so on.

If you have tight valves, swap those to an appropriately thinner shim; in most cases it's only one size; sometimes two.

They are only case-hardened, and not very deep at all. We've had this discussion more than a few times since I've been a member of this forum; and about two or three years ago a member who is a metallurgist sliced one and posted an electron microscope photo that clearly showed how "thinly" they're hardened.

BAD idea. Get ahold of HogFiddles or XJ4Ever and get some shims. Don't risk blowing up your motor to save a couple $$.

 

Thank you all for the excellent advice. I'll have to look into that shim pool you mentioned.

 

And now, for the other side of the coin. Almost literally.
I have an XJ and 3 XS 1100's and I and a couple of other members of that forum grind the shims to achieve a more even clearance between valves (Each of us happens to have access to a surface grinder)
When the shims are manufactured, they are probably done in a batch mode, with the hardening process being a bath type heating process, (Cyanide salt or gas) which will penetrate all surfaces.
The reason for the hardening is to maintain a difference in hardness of more than 5 points Rockwell between the two rubbing surfaces, which will prevent galling. The harder surface becomes the sacrificial surface because of the lapping action of hard particles imbedding in the softer surface.
Which should prompt everyone to run clean oil.
Guess which surface is harder?
And easiest to replace?
So if the wear surface of the shim does not show wear, it is probably good for a few more miles.
But notice that the pressure of the valve spring is taken by a line of contact on the cam lobe, giving us a point load of "X" pounds per square inch on the surface of the shim and contact area of the lobe.
Obviously the pressure is not enough to displace the metal, or for that matter, to rupture the oil film between the two surfaces, since if it was, they would show signs of fretting, or scouring.
Now, lets look at the other side of the coin. (Shim)
We know that X amount of force per unit area is being applied to the top of the shim, and assuming the shim doesn't bend or flex, (don't grind then too thin), the same force is transferred to the contact surface between the shim and bucket. Since there is not any relative motion between the two surfaces, there can be no wear, and the forces applied cannot be high enough to swage the metal of either surface, since the line contact of the other side is spread out over the entire surface of the shim on this side. (If someone wants to do the math on that one, I'd bet that the ratio of areas is over 500 to 1. So 1000 psi on the cam side would be 2 psi on the under side)
So the trick of grinding is to grind the face of the shim that has the size printed on it, and contacts the bucket, and when done, use battery acid to etch the new thickness value on it, being sure to rinse and neutralize the acid before installation.
I measure clearance, take that shim out, grind, remark, and reinstall in the same bucket, just to keep every shim in it's original position. Figure that those two surfaces have been working well together for a long time, and there is no sense in breaking up a good team.
Another use for grinding shims is that you can adjust the timing of the valves, (trying to get them all the same), by selective thickness grinding on the shims. (That's for all the compulsive tuners)

Personally, I would rather keep the functioning set of surfaces together, rather than throw a different used surface in, (as in the case of a dealer shim swap) into the situation.
A new shim would probably not be a problem, but since those of us that use this method can get it done in a few hours, and not have to wait for shipping, new shims seem like a waste of time and money. And swapped shims are worse than what we have in there.
My advice is if you have access to a surface grinder, and know how to use it, go for it.
CZ

 

And now for the economics viewpoint. How much is your time and equipment worth? What more productive task can you accomplish in the time it takes to grind, clean, and remark one shim? Opportunity cost is always a factor. The only time when swapping out shims is not cheaper than grinding existing shims is when there are no replacments available (from any source). In that case grinding a shim becomes feasable because it involves less cost than making a new shim in a well equipped shop.

P.S. :roll:

 

Does that include time and gas down to the dealer?

:lol: CZ

 

Yes. I live in a small town. If I call ahead they'll even deliver for no fee.

 

dear Mr. Zap, horse feathers, you can't adjust valve timing with shims. [edit] never mind i read that wrong
just in round numbers a cheap surface grinder without tooling costs about the same as 300 shims.
do you make all your nut and bolts too?

 

I don't re-use shims; I just buy new ones.

 

I truly appreciate CaptonZap's descriptive reasoning for NOTswapping shims. Obviously a fellow that finds metallurgy and machining to be thrilling and fulfilling. Congratulations on having a passion in life that can be so very helpful.

However I agree with K-Moe :roll:
:lol:

 

Well, yes I have.
The exhaust nuts on an XS11 (XJ 11) have a hex (Allen) socket in them, and are rather short, and prone to abuse from PO's that don't know that there are metric and SAE hex wrench's, and they don't interchange. And if the wrong size is used on a recalcitrant (rusted) nut, the internal hex can become rounded, which can cause consternation and foul language.
So, some coupling nuts of the proper size, drilled out on one end to a size a few thousandths larger than the distance across the flats on the wrench, and a straight section of a hex wrench ground hollow on the end, using an arbor press for a broaching machine, all become the means to make nuts that can use the hex wrenches, or a regular box end.
Now by all rights, I cant say I made the nuts, but I definitely modified them, and I have made nuts for things other than motorcycles, so maybe that counts.
While I appreciate you folks that don't want to be bothered with the, you'll pardon the expression, nuts and bolts of obtaining parts for your bikes, know those of us that do will be more than happy to take your money for supplying parts that you could make yourself. 8)
Clutch and throttle cables come to mind. But you get the point.

And if you read my original missive, you will note that I said "have access to ", which does not imply that a grinder has to be bought to be used. I'm sorry that you don't have access to machine tools, because it opens up a broad array of possibilities, and outlets for creative endeavors in the motorcycle arena.

CZ

 

New shims cost less than $10.

I have access to machine tools, but I also buy OE clutch and throttle cables.

The exhaust nuts on most XJs have an internal hex that nobody knows is there; I just buy replacements when necessary. They're available, and cheap.

Clutch and throttle cables are a matter of opinion and choice; exhaust studs are an easy fix; but a shim failure of any sort can do an incredible amount of damage. Grinding shims is an old race-tuning trick; however race motors don't have the same expectancy as street motors. The only time I've ever personally seen the spectacular results of a spit shim was in a race motor where shim-grinding was being practiced.

So grind on.

Personally, I keep my 30-year old motor maintained with "store-bought" factory parts, so I don't have to give a second thought to running it to redline whenever the mood strikes.

And I still don't recommend grinding shims.

 

Yes, and do you know WHAT caused the "spit shim"?
Correlation is not causation.
Some one putting the shim wrong side up could be a cause. Or any other number of reasons.

And your buying new parts is your prerogative.
The original poster asked if the shims could be ground, and whether they were case or through hardened.
Either way, they can be ground. They could be ground if they were annealed. Would it be a good idea? :cry:
My answer was to show that with a little thought, and to know the circumstances that it would operate in, a shim could be ground without worry. Can someone, who isn't knowledgeable about the process, cause a lot of grief? Does a bear scat in the woods?
How many riders are competent riders? Do you tell the ones who aren't to not ride?
Or do you explain the whys and wherefores of the process, and let them make up their mind as to if they should do it or not?

It's nice that you keep the newbys on a safe course of action, and the parts supplyers appreciate it too. :lol:

CZ

 

Granted; it was a race motor and there are a myriad of possibilities.

There are also a long list of valid reasons that shim grinding isn't recommended nor rarely practiced.

I keep myself on a safe course of action; then share the experience.

 

keep up the good work Zap

 

"Faint heart ne'er won fair maid".

Bunglejyme, if you have the facilities, and the know how, my opinion is that you will get a closer match on clearances by grinding, and no decrease in longevity.
Shims jump .002 in, and I can get within .0005 inch consistently in less than 10 minutes per shim. Lets see, at $10 a shim, plus mail wait time or drive to the dealer time, that equates with a shop rate of $60 an hour. Yep, I'll work for that. :wink:

CZ

 

so at 60$/hr how much you think you have in those exhaust nuts?
did you ever make any tire valve caps?

 

Can we clarify -
The shim is "Hard" - the cam is "Soft" but has picked up some hard bits.
Let's be generous and say the cam is now 20% hard bits embedded into soft metal. You still have something that is 80% soft rubbing something flat, that is 100% hard. Bathed in oil as well - why does the shim wear ??
Also,
Are you re-establishing the tiny radius at the edge of the shim??

 

Grinding or Machining a Valve Adjusting Shim is NOT recommended.

Fitting a New Shim - OR - using a correct one from a Used Shim Pool is OK.

 

Seems kind of counter intuitive, doesn't it?
Laps are a standard tool in the machining trade. A lap can be a copper plate, and you know how soft copper is, mounted on a face plate, and "charged" with bort. Or it can be an expandable split rod, used to laps bores.
Bort is small bits of abrasive, usually diamond, in a liquid carrier, or dry, depending on the use.
The bort is spread on the lap, and a hardened roller is used to imbed the bits into the copper or other soft metal. The diamond grinder bits you buy at Habba Fleight have an electro deposit on to of the bort, which hold the particles in position longer.
Laps are to smooth off the asperities left by grinding or machining. They are not used for gross stock removal.
Apply all that info to the cam / shim interface. Anything hard enough to get imbedded in the cam, acts as a gouge every time the cam rotates.
What do they use to grind diamond? Diamond.
So anything AS HARD, or harder, than the shim, can become an abrasive particle embedded in the cam, which acts as a lap. Carbon, and diamond is a form of carbon, can be formed and entrained in the oil of engines. Not all of it is hard enough to pose a problem. But the possibility remains that some can find it's way into soft metals, (aluminum pistons?) and become a faux bort.
Every time there is relative motion between the two surfaces, the particle can "plow" through the oil film, and scratch the surface. Just like sandpaper. Enough times, and you have measurable metal removal.


Keep your oil clean!

And any machinist that doesn't "break" the edges of a machined piece, needs to go back to apprentice status. Of more importance is the bevel or radius on the edges of the cam lobes. They prevent a sharp edge from fracturing and depositing a chunk of metal into the oil stream.

Look at the situation with crank shafts with plain bearings. How can a journal become undersize, if it is running on a babbit beraing? And babbit is softer than copper!
Given enough revolutions, running in dirty oil, the steel surface is actually lapped to a smaller diameter.

Hope that explains things.

CZ

 

Goodness, I really stirred up a hornets nest? (lol).
In my original post I did fail to specify what side of the shim I was intent on grinding. My intention was to grind the 'down side" (i.e. the side that faces the bucket). AKA the side with the printing on it. In my case the most I would need to remove is .002" to .003". Case hardness usually exceeds that depth. Moreover, the under surface of the shim is not exposed to the wiping action of the cam lobe and the potential for fretting. Recycling used shims sounds like good economy but I suppose that all depends on the condition of the cam contacting surface. BTW my background is in Tool & Die. I have both shop and design experience in that field. I am a machine designer and have over 30 years behind me in the field.

 

So far, all I've heard is " don't do it because nobody does it, and it shouldn't be done, and the factory says not to do it".
Is there any logical explanation, based on sound physics, that says why it shouldn't be done?
Or just the factory covering it's liability position, and insuring that it sells some high priced parts, and everyone parroting the factory line?
We wouldn't be here talking about this if Gottlieb Daimler and Wilhelm Maybach had not said "Huum, :idea: I betcha if we took old Otto's engine, and put it on this wooden bi-cycle, we could make something cool".
I'm sure that everyone said "You shouldn't do that, nobody else does, and it will scare the cows". :wink:

Kinda sad to see American bikers getting so wimpy. :cry:

CZ

 

All this over a shim that can be replaced for about $8.

For me, personally, "the factory said not to do it" is reason enough. I trust Yamaha to have me out-engineered at every turn.

 

Thanks, that expains a lot.

In this case, it sounds like I'm preaching to the choir.
As you know, even going through the case would not have a deleterious effect on the functioning of the shim.
One other thing, about marking the shim.
I mentioned using acid as a marking agent. Everybody has a battery with acid in it. That was for those who do not have access to an electro marker. And I'm sure that you know what I'm talking about.
Actually, since you can grind what you want, there is no reason to mark them, since the next time they need adjusted, you measure the gap, measure the shim, figure out how much to take off, and go from there. This assumes that you are going to be the next one in there. If you are going to sell the bike, it is nice to let the next mechanic, who doesn't want to grind, know what size it is, and mark it.
Let your conscience be your guide, I've stated my position. :lol:
If you do decide to grind, let us know if you experience any problems, as I can always rethink my position, given valid reason.

And the nay sayers can gloat. :twisted:


CZ

 

Once you've ground down the shim, how well will it react to the bending force being applied by the cam, now that the outer surfaces of the shim are no longer uniformly hardend?

 

My experience with OEM manufacturers indicate that if a process is not absolutely needed, then it won't be done (depends on the level of "quality" being sought, of course). Each few pennies saved over a million+ units of production adds up really quickly. We pretty much know that Yamaha drivetrain engineering standards and performance were quite good (their electrical engineers, not so much), so second-guessing their experience and man-hours of development and access and time on testing may be hazardous to your engine health (perhaps)..............

 

What is the shim setting on?

What percentage of the thickness did you remove by grinding two or three thousandths off?

Will that removal seriously impair the strength of the shim?

CZ

 

I'll asume that you don't know since you only have more questions. I don't have the answers either, but since you actively practice shim grinding I thought that you might know.

I don't want to come off as flippant. I really am interested in why a method, that is counter to everything I've been taught about valvetrain maintainance, is acceptable.

 

I answered the way I did as a method to prompt you to use your powers of observation and analyze the situation.
The shim sets in the bucket, and while I haven't measured the thickness of the bucket top, I assume that it is more than paper thin. The shim sets on that surface, and it provides support for the shim. It is flat, and if the shim bottom is flat, there is no flex of the shim. (Well, actually there is some bending in both pieces, since all metals bend when stressed, but it is so minute that you would be hard pressed to measure it.) The force from the lobe is slightly off center of the bucket, and the valve stem is centered under it, so the force of the cam lobe is pinching the two thick nesses of metal between the lobe and stem. Almost no bending moments there!
I don't have a shim out to measure, but if memory serves, they were about .100 inch thick, depending on what thickness they were ground to at the factory. So a 5% reduction in thickness, that is .005 inches, or .127 mm, would reduce the thickness by 5%
When mechanical devices are engineered for public consumption, there are usually designed with a safety factor as far as ultimate load. Bunglejyme can probably give you a precise number, since he designs machinery, but it is usually more than 200%. So if we reduce the thickness by 5%, even if we say that the total strength was reduced by that amount, (and it won't be. Check beam strength calculation in any engineering handbook), we are still within the safety margin.
What you were taught is what the factory would like you to do. It's reasons are not mine to know, I guessed at two in a previous post.
I do know that there are a lot of people who claim to be good mechanics that employ practices that make me cringe, and if I were to say "yeah, do it this way", and they were not knowledgeable about the fine points of the process, there is a good likelihood that they could omit a vital detail, and the outcome would prove to be a failure. If my reputation was dependant on a good outcome, I would be hesitant to allow the unskilled worker to employ that process.
So I can see why Yamaha advises what it does. They can control what goes into, thus what happens to their product.

Besides, most motorcycle mechanics are not machinists, and few have a grinder.

You are the captain of your own ship, do as you think best.


CZ

 

Mr.Zap here's a thread you might be interested in
http://xjbikes.com/Forums/viewtopic/t=2 ... art=0.html
i know from making the dovetail cutter for this that sometimes we do things just because we can, even though their not practical.
but i mean really, a 8$ shim? and you have other bikes to ride anyhow.
at least use your talent for something a little more valuable

 

that didn't work very well, did it

 

Cute! The only question I have is why didn't you round off the new post to match the other one. :wink:
Don't you just hate people who screw up carbs?

I read the thread, and the only two on it that I would consider worth listening to were Militant_Buddhist and mirco. And even they seem to be ignoring the physics (geometry) of the thing. There are no bending forces involved.
Take a plastic cap from a gallon milk jug. Place it in the table, top up. Press down in the middle.
It bends, doesn't it? This is what you guys seem to be afraid of.
Now take the cap, and put your thumb inside the cap, and your index finger on the top. Imagine that your finger is the cam lobe, and your thumb is the stem. Push down with your finger. Does anything bend?
And yes, I know the answer to that question. :roll:
As far as the chamfered edge, 3M makes a wheel for a bench grinder that is, for lack of a better description, compressed Scotchbright. It takes me longer to type this sentence that it would take to run the freshly ground edge of the shim around and around against the wheel and come up with the prettiest radius on the edge that you will find.

Frankly, I'm getting bored with this thread. You folks seem to have your religion, and it's dogma, down pat, and you are welcome to it. The guy down under, who pays exorbitant rates for parts, might want to be a bit more heretical, and grind shims. Done properly, there is no "down" side. ( That's a pun, son :lol: )

Ride on, CZ

 

From what I've read, I didn't see any reference to what is actually wearing. It's not the shim that is wearing, it's the valve seat. I also would like to point out that there is another option to shim grinding and that is to grind the the end of the valve stem.

 

In case anyone wants to know -
a cylinder will stop firing at 0.0015" of clearance. (cold)
At operating temps, the valve is continuously held open.

 

Is the origin of that little tidbit personal experience?

 

I have to disagree with this statement. my xj750 valve clearances open up as the engine warms up. I know this from personal experience. my bike would barely run till it got warmed up and at ambient temp, there was almost no lash, whereas when the engine was warm I could measure a clearance above 0.015mm

CN

 

Was yours the intake or exhaust??
turns out mine was the intake. I just checked.
- -
While riding at highway speeds, I felt a cylinder "go away" and then babied it home. I saw 100 PSI cold when I was fixing it.

 

My 900's Valves are adjusted to I-.004 ~ X- .006.

Even running 20W/50 with a couple mouthfuls of extra Oil added to the Sump; I'd hear ticking a bit louder after getting surrounded by cars barely moving in Summer traffic jams, ... with aggravated Cage-commanders deliberately narrowing the running room between cars.

When Summer turns to Fall and temperatures drop to the Mid-50's, ... my Oil Light would come-on as the cooled-out Engine made Scavenged Lube Oil flow a bit slower triggering the Low Oil Light to blink or come-on full.