woppi
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posted November 02, 2007 02:41 AM
stock rods ----- carrillo rods ---change bolts ???
a big question ????????????? had some debate with my buddys !!!
" kawasaki zx12r "
if you open your stock rods --- and build them again together ---- should i change the stock bolts ??
if i open carrillo rods ---- and build them again together -- whats about these bolts ???
change ore not ????
please give you argument
thanks
woppi
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Y2KZX12R
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posted November 02, 2007 02:53 AM
 Edited By: Y2KZX12R on 2 Nov 2007 04:12
It's more important to make sure your rod caps are mated properly. I have reused the bolts 3 times on a 1375 stroker and still get proper stretch. ANYONE who puts engines together should have a stretch gauge.
Have a shop that knows how to resize rods check them, particularly the cap parting line alignment. And give them the new bearings and the crankshaft if possible or at least the very accurate journal sizes so they can size the rods properly for good clearance. Run the bearings on the loose side to provide plenty of oil flow (rod and crank cooling). Typically .0028". Karl, isn't that what we set all of yours too?
And don't run thick oil. All it does is reduce cooling. If your oil pressure at an idle is low never use a thick oil to boost it. Turn up the idle speed instead. Bearing wear doesn't happen at an idle when the compression and rod bearing load is almost zero.
These stock bike rods align with the bolts are don't align well. Kawi will tell you to change the bolts. But if you check rod bolt stretch (you should) you can see a bolt that doesn't stretch properly long before it will give you trouble. Even a new bolt can be bad and stretch too much or not enough.
Carillos are less prone to cap shift due to the dowels but they still should be checked and honed if needed. I've resized several sets of Carillos and have seen oval and misaligned caps.
This cap shift it the main reason people are snapping rods off and if there lucky just spinning rod bearings.
Check them. Every time!!!!!
And throw out that plasigauge. That stuff is crap.
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entropy
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posted November 02, 2007 03:42 AM
Edited By: entropy on 2 Nov 2007 09:00
warning: entropy doesn't know what he is talking about, and often doesn't listen carefully to people who do.
*********************************************************************************
with that said...
I try to set my rods up loose, like Jim says at .0028 or so and run 50W full syn. This last build i could only get .0022-ish and am running 40W.
I know i am kidding myself with oil weight/rod clearance, but doing this makes me feel like an expert so i do it 
Like jim says throw away the plastigage, it never gave me reproducible results and doesn't even taste good.
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posted November 02, 2007 07:44 AM
Karl, correct that....... .0028" !!! add a zero!!! 
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entropy
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posted November 02, 2007 08:01 AM
Edited By: entropy on 3 Nov 2007 00:38
quote:
Karl, correct that....... .0028" !!! add a zero!!!
oh shit!
you mean bearings are NOT supposed to have 28thou clearance???
maybe that's why my motors don't last???
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madmike
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posted November 02, 2007 11:53 AM
your supposed to check that stuff???
hey if you dont mind me asking, what should the bolts stretch too? and I have always used 20W/50W or 15/50... why should I switch to a lower rate oil? I just thought the thicker oil would be better protection in general...
Thanks!
MM
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Y2KZX12R
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posted November 03, 2007 04:01 AM
Typically you want .007" per inch of bolt length. So you should see about .013" of stretch.
So what I do is torque the bolt to the recommended 16 ft lbs. and mark or note the nuts clock position. Then tighten the nut the 120 degrees (two flats) the book wants and check the stretch. If the stretch is above about .016" or so it's stretching too much and the bolt has lost some of its tensile strength and should be replaced. You want to make sure the threads and friction surfaces are clean and oiled before doing this.
Again if you replace a bolt you then need to start all over and recheck the cap alignment with the bearing in and the rod torque. So you really need to torque the bolts twice anyways just to build the engine so the one time torque that kawi tells you are imposable anyways.
Now you can see why its a PITA to get this stuff 100% correct and why so many people are blowing up "strokers".
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woppi
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posted November 03, 2007 02:24 PM
thank you for your arguments !!!
but sorry i understand nothing !!!!!!!!!!!!!!!!!!!!!!!!!!!!
woppi
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ninja12
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posted November 04, 2007 12:35 AM
Edited By: ninja12 on 4 Nov 2007 01:36
You must torque the rod to check clearance, then you must torgue for the final assembly.
Even if EVERTHING is right that's 2. what happens if it tight when you check? 3?
What if you want to verify your numbers? 4?
That's a little extra for one time use bolts.
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Y2KZX12R
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posted November 04, 2007 04:40 AM
They are not really one time use bolts.
These bolts can be re-torqued several times as long as you check the stretch vs angle. If the stretch is good then the bolts are fine.
As I said before the reason for most bottom end failures is typically poor rod cap alignment creating tight clearances at the parting line causing excessive heat buildup causing rod bearing and or rod failure.
Only replacing the rod bolts with new ones and plasti-gauging the oil clearance (top and bottom) is a sure fire way to blow it up.
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tcchin
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posted November 04, 2007 09:04 PM
Y2K - Is measuring elastic deformation sufficient for quantifying the bolt's condition in terms of all potential failure modes? Even fatigue? Do you have any tensile stress numbers to which .007"/in equates? Isn't stretch vs. angle dictated by bolt thread pitch, making it almost irrelevant? I thought stretch was used to verify tensile preload in the bolt and to verify preload from an applied torque.
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posted November 05, 2007 03:56 AM
Your just using stretch to verrify the bolt is still good. Your varrifying that the bolt is still stretching the same as kawi wanted it to. A bad bolt will not stretch properly, telling you its bad and needs to be replaced. Its not that complicated.
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tcchin
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posted November 05, 2007 12:32 PM
quote:
These bolts can be re-torqued several times as long as you check the stretch vs angle. If the stretch is good then the bolts are fine.
My point was that stretch vs angle doesn't tell you anything because the thread pitch determines stretch vs angle in the same way that adjusting your drive chain the same number of flats on both sides maintains your wheel alignment. From my experience, the reason you measure stretch is to verify that the tensile preload applied to the bolt is appropriate for the amount of torque that was applied to the head.
Stretch vs torque will verify the yield strength of the material, as well as verifying that there is no necking-down the in bolt. This test will not verify that the bolt will not fail from fatigue loading. Fatigue loading is cumulative, so even if a used bolt passes elasticity, x-ray and magnaflux tests, there is no guarantee that it isn't approaching its lifecycle limit.
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posted November 05, 2007 02:05 PM
I see what your saying. But there is no torque spec for the rod bolts on a zx12r.
These bolts are torque to yield. Its 16 ft lbs + 120 degrees of rotation. Thats the spec.
You could use a torqometer type torque wrench and read the dial when you get to the 120 degrees and aquire a torque reading that way I suppose.
The main thing is to see the proper stretch.
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ninja12
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posted November 06, 2007 02:58 PM
What tool are you using to measure stretch?
Where can it be purchased and how much?
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Y2KZX12R
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posted November 06, 2007 06:12 PM
Heres a few from Jegs. the cheeper one will work just fine. You need to drill a tiny dimple on both ends of the rod bolt with a 1/16" drill bit. Just enough to get repeatable measurements.
http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_762354_-1_10783
http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_753951_-1_10783
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MadMike
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posted November 07, 2007 05:07 PM
can you expand a little more on the oil issue?
thanks...
MM
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posted November 08, 2007 10:05 AM
Sure Mike, the oil flow thru and past the bearing surfaces cools the crank and rods. Without enough oil flow the crank and rods heat up and eventually will spin a bearing or worse.
Thats why running thicker oil isnt always (and rarely is) better. Contrairy to popular internet myths thicker oil doesnt provide any better protection from metal to metal contact unless you run extremely high oil temps. But it does flow less thru the bearings for cooling, thats why you see oil pressure rise with thicker oils and or a cold engine.
If you want to bring up the oil pressure at an idle, turn up the idle speed. Using thicker oil just pushes more out the relief valve and less out thru the bearings for cooling all while you see a higher indicated oil pressure. So it makes you feal good but doesnt help your engine.
Believe it or not the engineers know what weight oil is best for the oiling system to do its job best. I know that sounds crazy, but they realy do know a thing or two.
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posted November 08, 2007 02:08 PM
Just read on Brocks site he like 5w-30 up to something like 225hp then 10w-30 up to 500hp. Hp numbers may be off a few , but the principle is the same light oil works.
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KZScott
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posted November 08, 2007 11:16 PM
I learn something cool every time i log into this place....gotta love it
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