whitehendrix
Zone Head
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Posts: 757
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posted September 08, 2009 04:05 PM
 Edited By: whitehendrix on 9 Sep 2009 00:06
main bearing shell/journal madness
ok. calling all engine builders..
i have an 05 636 in surgery. kid wiped out on a wheelie and ran it home with a cracked case.. therefore, no oil. killed #4 big end, but i suspect some main damage now..
i put new greens in the rods and they're perfect and in spec now, which i think is .0015''-.0023''. i'm at .0018" across all of them. my problem lies on the mains however.
what i need to know is is there a smaller O.D. than the blues?
they're calling for .0004-0015 for the mains. the plastigage is showing .0015 and up. says that wit hthe "#1" satamped on the crank and this blank and that makred and so on that the blues are the shells to use.
thing is, i am .001" too large.
i threw my digital sorta-cheapo (non Karl quality) calipers ( that were certified/calibrated when i was a machinist a year ago) and i'm getting 2.2185-2.2180".
the tolerance is 2.2190-2.220. so, i think thaeres my thousandth of an inch.
so, my thing is i'd like to close that .001 up with another bearing size (color) but am unaware of if theres anything more undersized than the blues.
i really do NOT wanna assemble it with .001 slop in the mains, and i doubt the boys wants to frop $800 on a new crank.
so, is there another set of shells that will allow me to close in towards .0004? i'd be happy with an overall of .001. thats about center of the tolerance.
if not, should i suggest to the kid getting a new crank? can this crank possibly be saved?
thanks!!
-Jim
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
  
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tcchin
Zone Head
Posts: 867
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posted September 08, 2009 04:19 PM
First of all, did you clean up the crank journals to make sure they're smooth and uniform? That's a good idea if the motor has lunched a bearing. Cleaning out the oil passages goes without saying.
Secondly, you should use micrometers for those measurements, as calipers just don't have the accuracy.
Thirdly, .0015" is not all that excessive for main bearing clearance. The journals are what, 35mm on that motor? Using one thousandth per inch of journal diameter would be .0014", so you're right in the ballpark.
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whitehendrix
Zone Head
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Posts: 757
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posted September 08, 2009 05:03 PM
yes sir, i spent a few hours at the tank cleaning and perfecting the cases. the journals have probably the same quality finish as they did when they left the factory. the bearings weren't spun at least.
my thing is, i don't have a mic that reads to .xxxxx or even .xxxx. 
thus why i used calipers.. then again, i've never had problems geetting accurate reading s with them.. the tolerances we were required to hold where i was a machinist at were retarded mil-spec numbers. it was a D.O.D. conrtracted shop..
my thing is i know some guys will build "loose" motors and run a higher flow oil pump to ensure float and oil presence, but thats not an option here.. i'm not sure if there would be enough oil flow to comp for the extra .001" spread across 5 journals in all.
i just really wanted to stay within the factory tolerance and not exceed .0015". the plastigage indicates .0015 -.0018. i hate being at the upper end of the tolerance.
thank you for your reply tim!
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
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dougmeyer
Needs a job
moderated
Posts: 2713
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posted September 08, 2009 06:35 PM
Nothing wrong with .0015 - .002, I wouldn't sweat that at all. Ditch the calipers and the plasti-gage. You really don't know WHAT you've got. Check Ebay for mic and bore guages. there are a lot of measuring tools on there, pretty cheap. At a minimum find somebody with some micrometer setting guages and check your calipers against them and find out how accurate they are.
Doug
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It's not that I think you're dumb, it's just that so much of what you know isn't true....
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whitehendrix
Zone Head
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Posts: 757
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posted September 08, 2009 06:47 PM
i have a set of telescoping bore gauges.. or did you have something else in mind?
i wasn't real sure how much importance .001 made on these being they're caling out down to .0004 for a low-end tolerance.. haha.
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
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icarus
Expert Class
Posts: 344
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posted September 11, 2009 01:02 PM
Whitey, I have a barely used set of 0-6 mics that read to .0001. They are an import brand
(china) and come in a wooden box with calibration pins. If you are interested send me a pm
on Weldingweb.com my screen name is bart. Later...
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tcchin
Zone Head
Posts: 867
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posted September 11, 2009 02:45 PM
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94873
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=98485
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95918
I prefer digital micrometers to analog, because reading the number directly off the display is always easier than interpreting the number off the scale and the barrel. The digital ones also switch between in/mm and will zero anywhere so you can do differential measurements or use accessory anvils with ease. You can find a lot of used mics on Ebay, as Doug pointed out, but the 1-2" range ones are harder to find than the 0-1" ones.
Telescoping gauges require some technique to use accurately. If you can use them, all you'll need is a mic and a mic stand, and you're in business.
.001" makes a huge difference if you're using it as a tolerance. In this case, you've changed the basic dimension from .001" to .0015" and changed the tolerance from +/-.0005" to +/-.0001". If you were to use .0015" +/- .001", I might have to drop by your place and hit you with my purse.
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whitehendrix
Zone Head
fails!
Posts: 757
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posted September 11, 2009 07:41 PM
thanks icauus! i'll hit ya up when i get a chance. much appreciated.
Mr. Chin, i assure you i try to operate on a "no tolerance" mindset.. lol the last thing i want is the Purse of Justice to be utilized.
like i said, they called for .0004-.0015". i really wanted to fall in between that. no more than the most, no less than the least. i was coming in at .0015 and over.
many people since then have said they'd throw it together as-is and not even sweat that extra .0005 i'm seeing.
i do like the digital shit as well. parralax is a bitch. 
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
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