750B valve adjusting shims uh-oh

Woops:blush: meant LOW carbon steel, case hardening turns the surface to HIGH carbon steel(need to proof-read better-says to ones self). But you did bring up an interesting question. Is the case hardening done before or after said factory grinding and polishing. I'll do what I can to find that one out unless you have some insight to that Steell. Thanks for calling me out on that one!

Steell,as far how I based my conclusion that grinding and polishing occurs before case hardening is that a new unused shim (the ones I saw)were completely brown to blackish color and if you look at a used shim where the cam rides the shim its been "polished" bright and shiny. So if case hardening occurs before grinding and polishing, the two sides of the shim would be shiny. Hey, I could be way off base here but I'm just trying to find out if like you say some hardening has already been removed to make a specified thickness shim or has the hardening basically been untouched hence we got more room to work with.

I have just been doing some research, and I have not found any case hardening treatment that results in a brown or blackish color. Maybe it is some form of rust protection?

I did run across something that you may be interested in reading though

www.tech.farmingdale.edu/depts/met/met205/casehardening.html

I found it interesting anyway.

I did find that some forms of case hardening distort less than others, so those may not require grinding.

I'm no expert, I'm not even sure I qualify as a novice

The shim-under-bucket shims are hardened also. I ground one as an experiment. It definitely gets easier to grind once you get past the outer shell.

Hey LOUDHVX, Do you have any idea how much you ground off before hitting the low carbon center?

I talked with my step dad who retired from a large machine tool co. here in WI. He said generally speaking they ran across case hardening usually at .016 of an inch, but recommended not grinding any more than .008 of an inch (half). I only need to grind at most .005 of an inch. He said given the limited availability of these particular shims, he would not hesitate to have shims ground and make sure the ground side goes down in the bucket. He said the true strength of the shim was the low carbon center and the hard surface was to make the shim not wear out on the cam side. He did preface this with the fact that different methods of case hardening go to different depths. I wonder if any of the major cam companies (ie. crane) could shed some light? I'll have to give that a try.

Steell, when I was researching case hardening the other night I found a color chart pertaining to color relating to depth of hardness (went fom pale yellow-thinnest to blue black-thickest). IF I can find it I'll post it here (I was all over the place reading alot of different info)

OK,
I just took 4 out of one of the kz750 twins,
they are 280,280,265, and 260
if anyone needs them email me.
peace,
michel

Hey Ronjones,
What are you talking about "what he has listed is not..."?
I have at least 2 kz750 twins here...
michel

74cb750 wrote:

OK,
I just took 4 out of one of the kz750 twins,
they are 280,280,265, and 260...

Unfortunately, those are the larger sizes which are more readily available. They are still kinda rare though, and you are clearly a swell guy....

74cb750 wrote:

Hey Ronjones,
What are you talking about "what he has listed is not..."?
I have at least 2 kz750 twins here...

I'm pretty sure he means that the eBay listing link you posted (back on the other page) is for shims for 750 fours.

74cb750 wrote:

Hey Ronjones,
What are you talking about "what he has listed is not..."?
I have at least 2 kz750 twins here...
michel

He was talking about a link you posted (I think it was you anyway) to an eBay seller that had some shims. I checked the Link out and couldn't find any 750 twin shims either.

He wasn't saying you don't have any 750 twins

Unfortunately, those are the larger sizes which are more readily available. They are still kinda rare though, and you are clearly a swell guy....

I agree with that also

steell wrote:

74cb750 wrote:

Hey Ronjones,
What are you talking about "what he has listed is not..."?
I have at least 2 kz750 twins here...
michel

He was talking about a link you posted (I think it was you anyway) to an eBay seller that had some shims. I checked the Link out and couldn't find any 750 twin shims either.

He wasn't saying you don't have any 750 twins

Unfortunately, those are the larger sizes which are more readily available. They are still kinda rare though, and you are clearly a swell guy....

I agree with that also

Yeah, 74cb750, What Steell and Toast said:). Why would I say you don't have the bikes you say you have? The shims the ebay seller was selling were not 32mm diameter shims and I didn't find any 32's in his store, either.
BTW, those shims you took out of yours are the same sizes I took out of mine.
Kind of funny I couldn't remember what I wrote that you were calling me on:). Thanks, Steell and Toast,
for reminding me.
RonJ

FWIW, gas nitriding is a surface hardening treatment that results in a dull grey color... (and lapping would result in a flatter, smoother finish than grinding, in general)--though nitrided surfaces are generally not re-surfaced, rather replaced, when worn.

These days, I believe there are other, more hi-tech surface hardening treatments out there, but which might have any appropriate application in this instance, or not, I really have no idea about...

I think at this point we need a metallurgist to step into the conversation