valve shim case hard thickness

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barncat

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finishing up the top end work on my related '83 GR650 (cousin to XS) with shim and bucket valve adjusters.

anyone have experience as to the thickness of the case hard layer on bike shims in general, or whether they are through hardened? after the valve work, i'm considering "lapping" .0005"- .001" off the underside of 3 shims with 400 grit paper taped to my granite surface plate. have seen conflicting opinions on trying this but they are originally manufactured on a surface grinder one assumes.

the valve spec is .001"- to .003" clearance. i don't have a .001 feeler gauge and .002 is a no go. buckets can be rotated when cams are at adjustment position but there is some drag, so i'm guessing clearance is under .001".
 
It was always a BIG NONO to try and thin shims on Kawasaki fours. Especially shim over bucket, where the cam lobe could grab the shim and spit it out. Don't do it.
 
Hi barncat,
perhaps racerdave is right about Kawi fours but your shims are what?
Mebbe 1/8" nominal thickness and they are all surface ground at the factory in the first place to get the different final sizes.
Dunno of valve shims are case hardened, through hardened or just made from tough material but FWIW,
Nitride case hardening is perhaps 0.002" thick while carbon absorption case hardening is perhaps 0.008" thick
but if the shims are in fact case hardened and you want to thin down the shim with your lapping technique
I'd suggest you lap the shim's non-hardened underside. It's got the size marked on it and that'll be wrong afterwards anyway.
Gawd! Can't you find replacements instead?
 
i figure most of us on the forum own a variety of bikes, hence the Q...

racerdave and fred- my OP stated i'm considering lapping the underside of the shim(s), not the top chamfered surface which is critical. all valve shims are undoubtedly hardened, it's just a matter of depth of hardening. if you don't cut through that layer and keep your work flat there is no difference between dusting less than .001" off the bottom or swapping in another shim. valve clearance spec on this motor is tiny.

i'm pretty sure these shims, if you can find them, are in .05mm steps which is over .001" and more than i need off. actually, one shim is ok as is and what i could do is just swap 2 of the 3 in this case, so i'd only need 1 fresh shim. that route makes more sense, but i'm still curious re hardening thickness.
 
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My experience with shims.........go to the dealer/service, the parts person is of no use to you here, ask about the box of shims in the garage/tech area, they keep them in a box, usually not even inventoried. Yes the new ones were made in different sizes in increments but the ones used in the engine when they were new are sized in-between these increments. You should be able to find the size you need new or old. Take your mic or calipers with you.

Scott
 
closest Suz dealer to me is 50 miles one way. this area is very underserved for bike dealers other than Harley stuff. just swapped shims and ordered a 2.55 shim on ebay- where you can almost always find whatever... it'll be several business days though from CA. i would not have tried to reduce a 2.70 to 2.55. numerous other phases of build to work on in the interim.

upon close inspection, both top and bottom edges of the shims are chamfered, and all surfaces are extremely hard including the bottom. a very light test pass on an edge with a sharp fine file won't even begin to touch it. if there are any motor builder metallurgists out there, i still think you could knock .001" off if you had to. could not find anything specific online.
 
If your Suzy takes 25mm shims, you can use Yamaha, Honda or various car 25mm shims. No, there is no upside or downside to the shims. Some people put the markings in a certain orientation but it doesn't matter, heck they need to be measured anyway. The most common price for shims from the back room is currently about $4 per shim.

Scott
 
weasel- duly noted. these are probably going to end up in the mid range.

mrtwo- yes technically you're right. i suppose convention dictates putting the markings down so they don't wear off but calipers or a mic are the final word.
 
On a Suzuki (shim over bucket) I had the previous owner had noted down in the workshop manual the size and location of each shim. It was just a simple drawing. He also gave me a homemade bucket depressor and a length of 0.001 shim stock (that he said was hard to get).

Knowing what size shim was where made shim selection a lot easier next time and sometimes they could be swapped as you have done.
 
barncat said:
- - - upon close inspection, both top and bottom edges of the shims are chamfered, and all surfaces are extremely hard including the bottom. a very light test pass on an edge with a sharp fine file won't even begin to touch it. if there are any motor builder metallurgists out there, i still think you could knock .001" off if you had to. could not find anything specific online.
Click to expand...

Hi barncat,
I doubt that the hand lapping technique will work too well for you.
It's been over a half-century since I last used a surface grinder but borrowing the use of one would be the way I'd go.
Set the shimming disk up on the surface grinder's magnetic chuck, put a strip of steel plate front & back of the disk
to stop it being spat out and kiss 0.001" off it. But first you'll need to add a "bro with machine shop" to your buddy list.
 
The shims are all marked for size. I just made a .001 feeler out of some thin spring steel. A surface grinder would be best way to take a bit off, with shim nested in a circular steel cutout. Magnetizing the shim is not good however...
 
Over the years, I've ground down a shim or two on my GSs, no big deal with a modicum of care. Such were the delights of living in the sticks, pre-internet. I wouldn't bother doing it now, though.
 

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