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Offline Jonny Hotnuts

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bearing question
« on: February 04, 2009, 08:29:34 PM »
I have a shiny spot on one of my crank bearings. It is perfectly smooth to the touch.
There is no mark on the journal. Should I replace the bearing?

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Offline Milwaukee Midget

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Re: bearing question
« Reply #1 on: February 04, 2009, 08:50:33 PM »
It bugs me that it's on the top side.  Jonny, refresh my memory, what engine are we looking at?  No other problems with the rest of the mains?

You got it apart, so yes.  It could simply be an out-of-round bearing insert.

But I'd also check the crank for straightness, and maybe polish the crank journal, but I'm real picky on this kind of thing.

How are your clearances?

Are we looking at the front or back of the engine?  Front - check harmonic balancer.  You running any accessories (alternator, oil pump)?  If it's on the rear, check flywheel/clutch assembly for balance and make sure your pilot bushing is centered.
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Offline fredvance

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Re: bearing question
« Reply #2 on: February 04, 2009, 08:54:05 PM »
Its a busa motor.
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Offline Jonny Hotnuts

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Re: bearing question
« Reply #3 on: February 04, 2009, 09:12:25 PM »
It is on the top side, outboard bearing on the cam chain side. The rest of the bearings looked as if they were off the shelf including the bottom side bearing mate of this one.

Could excessive cam chain tension cause this?
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"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline Stainless1

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Re: bearing question
« Reply #4 on: February 04, 2009, 09:30:57 PM »
Put a new insert pair in there and check it next year about this time...

No Cam chain tension won't cause it.  I vote for just a faulty bearing half if the crank looks good. 
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Offline interested bystander

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Re: bearing question
« Reply #5 on: February 04, 2009, 11:49:12 PM »
Noonan, Yacoucci, where are you? on this one.

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Offline 1212FBGS

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Re: bearing question
« Reply #6 on: February 05, 2009, 02:04:16 AM »
Quote from: Jonny Hotnuts on February 04, 2009, 08:29:34 PM
Should I replace the bearing?



Jonny please.... you see damage to a critical part of a high performance engine!  you ask if you should replace an $18 bearing shell?... do yourself a favor... don't cheep out!...
Kent
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Offline RidgeRunner

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Re: bearing question
« Reply #7 on: February 05, 2009, 07:58:02 AM »
     When I started out I would seek the advice of one of the best general mechanics/welders in town when I was in doubt on something.  Answers were usually "You'll never be any closer" and/or "Why is it you never have time to do it right the first time but always have time to do it a second time?".  They have served me well and continue to hold true for my experiences after nearly 50 years.

                  Ed Purinton
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Offline floydjer

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Re: bearing question
« Reply #8 on: February 05, 2009, 08:57:13 AM »
I know ZERO about bike engines , But,..Wouldn`t chain tension tend to draw the crank and cam towards one another? Seems like if it were tight the crank would move up/over. J.B.
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Offline Dean Los Angeles

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Re: bearing question
« Reply #9 on: February 05, 2009, 09:02:50 AM »
If you have gone to that much work to get that picture, then change the bearing. You aren't planning to take it back apart any time soon, so get it all done now.

There is no positive outcome to leaving it alone.
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Offline Rex Schimmer

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Re: bearing question
« Reply #10 on: February 05, 2009, 10:36:10 AM »
Dean,
I love your quote: "There is not positive outcome to leaving it alone." I'm going to use it!!

Jonny, I agree with everyone, you are there, polish the crank, check for straightness and replace the bearings. If you don't you will worry about them until you have the engine apart next year, that is if it doesn't come apart by it's self! and you are viewing the crank thru the new "viewing port" in the case.

Rex
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Offline Stainless1

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Re: bearing question
« Reply #11 on: February 05, 2009, 11:00:34 AM »
Jnuts, although this was not a "we didn't replace a bearing" deal, it is a Busa gone bad... rod failure on one of the made way too big motors.  They don't fail often but when they do....
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Offline Jonny Hotnuts

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Re: bearing question
« Reply #12 on: February 05, 2009, 11:55:25 AM »
I can assure you all that I ask if this is OK to leave this bearing in the motor not because I want to save money. I could see something like cam chain tension causing the crank to touch the bearing when the motor was not running and could polish the bearing during start up, like shown in the pic, before oil pressure comes up. I could see this happening without causing damage and being completely normal and would look like this 10 minutes after starting for the first time.

With that being said I understand that this in fact may not be the cause and will change the bearing, but I would like to know if I should change the entire set if the rest look perfect or is changing the one OK. Again this is not because I am trying to save money its merely due to not knowing if by normal use the bearings change stock tolerances or will they remain the same as a stock bearing.


ALSO....

Will be using the good rods.
(those look like stock rods in the pics stainless!)

 :wink:
« Last Edit: February 05, 2009, 11:57:37 AM by Jonny Hotnuts »
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"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline Harold Bettes

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Re: bearing question
« Reply #13 on: February 05, 2009, 12:17:58 PM »
JHN, :-D

I know very little about this particular engine, but I have a pretty reliable working knowledge of bearings and scary things that rotate in them. :-o

The pic shows an odd wear pattern that is opposite an oil hole. My guess is that the bearing is loaded more there but the oil wedge must not be up to the task of supporting the crank like it should. :roll: Perhaps one should take a look at the oil pump and make sure that the clearances there are correct. 8-)

Bearings are built with pretty good control of the diameters and thickness, but there are normal variations that are just part of manufacturing tolerance. The only way to assure that a new bearing has correct clearance is to MEASURE the parts involved. :?

Since cost is not the issue, simply try and re-fit a fresh bearing into service. If the clearances all turn out correctly, you won't have any problems with it. 8-)

Best of Luck with the project. :wink:

Regards,
HB2 :-)

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Offline Stainless1

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Re: bearing question
« Reply #14 on: February 05, 2009, 12:27:24 PM »
That set was Carrillo, three good ones left.... The next year we used Falicon, one of the soft plugs in the head popped that time, similar result, windowed the block in the middle.  Look at your head and consider modifying it to screw in plugs.... water is a poor lube at 9000 RPM
We quit running 2 liter class...
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