entropy
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posted August 08, 2006 07:18 AM
measuring stuff: bearings
As my 2nd motor, AKA the "Senior Science Fair" project continues, I am in the mode of measuring everything (twice, at least).
So I measured the thickness (not ID when mounted) of some rod & main bearings and guess what??
new blue rod bearing: .0009" thinner at the split than at the middle
new brown #3 main bearing: .0006" thinner at the split than at the middle
Y2K and some others prolly knew this, but I sure didn't.
Just thought I'd pass on this exciting "fact" 
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Y2KZX12R
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posted August 08, 2006 07:50 AM
Yep, a taper is normal. When the bearings are in the rod and crushed there is "oil clearance" and "side clearance". Oil clearance is top and bottom and side clearance is at the parting line. side clearance in an x pattern just above the parting line should be the same. If not then you have cap alignment issues. This cap alignment is best checked on a rod machine without the bearing halves in and the rod nuts torqued to spec.
The taper of the bearing insert varries depending on how much oil flow the engineer wants to cool the rod journal.
This is why when you take your bearing/rod ID assembled measurements you need to measure the "oil clearance" top to bottom.
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entropy
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posted August 08, 2006 08:38 AM
I just KNEW that you knew this stuff!!!
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Y2KZX12R
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posted August 08, 2006 08:44 AM
 Edited By: Y2KZX12R on 8 Aug 2006 09:51
Oh, another reason is to compensate for "pinching". Rods big end underload go egg shape and they pinch in at the cap parting line.
I was checking out another set of zx12r rods the other day and measured some cap shift on those as well. Not as severe as my set was but they were "younger" rods. They wernt blackened from metal transfer on the ID of the big end like mine were from 18,000 miles on the street.
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entropy
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posted August 08, 2006 09:29 AM
cool
another fun fact which Y2K knows full well, but i never appreciated is that the difference in spec thickness of blue vs brown is less than .0002" .
Compare that with the taper of .0006-.0009".
pretty cool. gotta be careful how you measure bearing ID for matching the "right" color bearing with that shiny newly ground crank, eh?
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osti33
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posted August 08, 2006 09:30 AM
quote:
Oh, another reason is to compensate for "pinching". Rods big end underload go egg shape and they pinch in at the cap parting line.
I was checking out another set of zx12r rods the other day and measured some cap shift on those as well. Not as severe as my set was but they were "younger" rods. They wernt blackened from metal transfer on the ID of the big end like mine were from 18,000 miles on the street.
Hmm. I wonder where the second set of rods came from. 
Good thread guys. 
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entropy
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posted August 08, 2006 09:56 AM
give a man a hi quality digital micrometer and he'll start measuring everything that doesn't require unzipping to get at.
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Y2KZX12R
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posted August 08, 2006 10:30 AM
Ryan, I'll be at Bills tonight. Hopefully your good to go.
Karl, I didnt know the two different bearings had a different taper.... See, we all learn somthing.
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entropy
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posted August 08, 2006 11:21 AM
Jim,
rods and mains might have different tapers or i might have been mixing Bud Lite and Mitutoyo
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osti33
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posted August 08, 2006 03:19 PM
quote:
Ryan, I'll be at Bills tonight. Hopefully your good to go.
Karl, I didnt know the two different bearings had a different taper.... See, we all learn somthing.
Cool. Let me know what you guys find out.
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Y2KZX12R
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posted August 16, 2006 03:30 PM
Edited By: Y2KZX12R on 16 Aug 2006 16:36
Karl, are you still measuring? 
Ryan, you should see your stuff friday maybe?
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osti33
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posted August 16, 2006 03:47 PM
Jim,
I got the parts today. Everything looks great!!
Thanks,
Ryan
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ninja12
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posted August 17, 2006 07:01 AM
Edited By: ninja12 on 17 Aug 2006 08:03
Could wear explain why Y2k had a round bore with old bearings, and not with new?
I would expect more wear in the top and bottom than the sides.
Y2k what did the new bore numbers look like after resizing?
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Y2KZX12R
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posted August 17, 2006 11:03 AM
quote:
Could wear explain why Y2k had a round bore with old bearings, and not with new?
Actually the rod big ends were still round. New or old bearings doesnt make any difference. When you measure the rod bore of the big ends its always without bearings in the rods. I didnt measure the ID of the old bearings in the rods, just the rods without bearings.
But yea, what you are saying is true. The bearings will eventually wear in at the tight spots.
But if you sustain high revs with tight spots at the bearings your going to build up heat and your asking to blow up the engine.
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ninja12
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posted August 17, 2006 02:48 PM
quote:
quote:
Could wear explain why Y2k had a round bore with old bearings, and not with new?
Actually the rod big ends were still round. New or old bearings doesnt make any difference. When you measure the rod bore of the big ends its always without bearings in the rods. I didnt measure the ID of the old bearings in the rods, just the rods without bearings.
But yea, what you are saying is true. The bearings will eventually wear in at the tight spots.
But if you sustain high revs with tight spots at the bearings your going to build up heat and your asking to blow up the engine.
Is this a normal conditions when the rod bolts are replaced?
How does resizing effect the bearing selection?
If it is changes (probably) are the changes documented or it it up to the builder to find the new size?
Maybe this explains why the 2000s had a extended breakin.
It would be interesting to see if the 2002 up suffer the same faith
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Y2KZX12R
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posted August 18, 2006 02:15 AM
quote:
Is this a normal conditions when the rod bolts are replaced?
How does resizing effect the bearing selection?
If it is changes (probably) are the changes documented or it it up to the builder to find the new size?
Maybe this explains why the 2000s had a extended breakin.
It would be interesting to see if the 2002 up suffer the same faith
Is it normal? Well I saw cap shift on my 4 rods and Ryans rods also. I'd have to say its common at this point. But the cap shift was there even before the bolts were replaced, thou not as bad. Remember the rod bolt shank are what actually aligns the cap.
Resizing, if done properly, doesnt effect the bearing selection. You would use the same size bearing you used before as long as the crank journal size hasnt changed. The big end bore is actually still the same size (can even be smaller) than before resizing. But if your rods were the bigger bore to start with then you would still use the bigger rod bearing.
I'm not sure if you could actually bring a big bore rod down to the small end of the spec without changing the center to center too much thus lowering the deck height.
As far as extended breakin? I'm sure the rods were concentric right off the sizing machine, so I wouldnt think it was an issue but you never know. We did use one rod with a newer part# to replace one bent older rod and it actually had more cap shift than the other 3 rods. But it actually had more blackening in the big end bore from heat transfer than the other 3 older par# rods. So thats what makes me think that the cap mis alignment issue is a cumulative effect over time and miles.
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ninja12
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posted August 18, 2006 07:16 AM
Might be a reason to just replacing all the rods with new when during a rebuild.
Ron Ayers has rods for $100 , resizing is $25 plus 20 for new rod bolts and nuts.
If you had crank damage you are probably replacing one anyway.
In the interest of time and comfort level for those who don't have all the tool and
knowledge to check everything it could be a real option to just replace all 4 new.
An extra $200 for insurance is not much in this game. $1000 for carrillo.
How much of a problem do you think the cap shift would be on a street bike that would
get the 1000 mile breakin again?
Doug Meyer stated that the rod bolts could be reused, what is your opinon on that?
Newer part number rod? 2000 and 2001 used the same rods, correct?
2002 up rod? If so are the the same weight?
Did you do anything to help oiling, especially the #3 rod?
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Y2KZX12R
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posted August 18, 2006 12:58 PM
Is that what new ones are? $100 each? Not too bad.
I think I paid more than $20 thou for bolts and nuts. Cant remember now what they were.
I'm not sure on the break in thing and what actually causes the cap shift.
Is it excessive heat? A lot of high RPM use? The splines on the bolts wearing?
Yea the rod bolts can be reused if you check the stretch, which you should do anyways.
I'm thinking that they want you to replace the bolts because the splines get loose and dont align the caps good anymore, and not for tensile strength. but i'm guessing on that. I retorqued a few of mine several times with the old bolts to see what happened and they pulled torque and had the same stretch after 3-4 times so I dont know.
I'm not sure what year the other part # rod is from. But the weight was within 1 gram total and the big end was within 2 grams.
The small ends were off a little on mine. Had to balance them all to dead nutz just the way i like things.
I didnt do anything to alter the oiling. I didnt see any problem with any of the bearings when I took it apart. I havent heard anything on a #3 oiling problem on the 12r, just on the zx11 engines.
Whats the deal with #3 on the 12r?
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osti33
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posted August 18, 2006 04:24 PM
New rod bolts and nuts are a LOT more than 20 dollars. Depending on where you buy them they are 80-100 dollars for 8 bolts and nuts.
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ninja12
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posted August 18, 2006 06:00 PM
$20 per rod = $80 for all 4.
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osti33
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posted August 18, 2006 06:20 PM
quote:
$20 per rod = $80 for all 4.
Ah. Now I get it. Thanks for clearing that up.
Also on another note. If you do decide to buy new rods they come with new nuts and bolts already installed.
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ninja12
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posted August 18, 2006 07:00 PM
Whats the deal with #3 on the 12r?
Nothing i can prove, but out of the 10-12 2000 zx12s in my area all but 1 has blown atleast once.
almost everyone of them died with #3. The other 3 (if i remember right) had center bearing
problems which took out the cases. Every combo From bone stock to stroker.
I have had 2 stock bottom ends go with #3 one took the cases, both less than 8k miles.
I have a set 02 cases now. lets hope this will stop the knocks.
Maybe you can find some info on WHY things changed.
cases changed in 2001 and 2002. (KMC claimed 01 change was for larger oil view window)
crank changed in 02
rods and bearings changed in 02
clutch basket changed in 02(nothing to do with blown engines maybe)
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