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Author Topic: Do crankshaft bearing tolerances need to match?  (Read 637 times)

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Offline Plzhalpimlost

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Do crankshaft bearing tolerances need to match?
« on: April 07, 2020, 07:54:10 PM »
Hi all,
I've tried to find an answer in the previous threads about bearings, but can't seem to find an answer.

I've got a Cycle X crankshaft and a BBBBB case, not that it matters much at this point.
Here are my bearing tolerance, with NEW bearings.

Points Side
.0017 BLACK
.0016 BLACK
.0016 GREEN
.0015 BROWN
.0015 BROWN
Stator Side

Seems like these, while pretty mixed up color-wise, are good tolerances. My OCD does hate that .0017 though, but I'm running a black shell already.

Do I need to loosen up the others to get closer to .0017 everywhere (since I can't tighten the black one obviously), or are these alright to run?

Thanks
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Offline 754

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Re: Do crankshaft bearing tolerances need to match?
« Reply #1 on: April 07, 2020, 10:32:39 PM »
I think you mean clearance,  not tolerance. What is the Spec in the manual ?
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Offline bryanj

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Re: Do crankshaft bearing tolerances need to match?
« Reply #2 on: April 07, 2020, 11:46:08 PM »
Simple answer NO
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Offline Plzhalpimlost

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Re: Do crankshaft bearing tolerances need to match?
« Reply #3 on: April 08, 2020, 10:05:38 AM »
Yes, CLEARANCE, not tolerance. Thanks.
Between .0008” and .0024”.

Also, I did this via plastigauge so these are rough numbers but they are definitely all between .0015” and .0020”.

Does anyone have concern over all the different bearing colors?


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Offline jakec

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Re: Do crankshaft bearing tolerances need to match?
« Reply #4 on: April 08, 2020, 10:15:54 AM »
the point of the different shells is to bring the clearances close together, so it shouldn't matter how random the assortment is if the clearances are close together. Also, with plastigauge you're measuring by eye so if you really wanted to you could measure that 0.017 and get 0.016  ;)
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Offline 754

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Re: Do crankshaft bearing tolerances need to match?
« Reply #5 on: April 08, 2020, 10:37:14 AM »
 So you are fretting over 2 TENTHS  of a THOU..
 Do you realize that is less than a tenth the thickness of a hair..
 It's within spec, move on..
« Last Edit: April 08, 2020, 03:21:19 PM by 754 »
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Offline Plzhalpimlost

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Re: Do crankshaft bearing tolerances need to match?
« Reply #6 on: April 08, 2020, 12:56:54 PM »
Quote from: 754 on April 08, 2020, 10:37:14 AM
So you are forgetting over 2 TENTHS  of a THOU..
 Do you realize that is less than a tenth the thickness of a hair..
 It's within spec, move on..
Ha! I appreciate the directness. Moving on. Cheers


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Offline 754

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Re: Do crankshaft bearing tolerances need to match?
« Reply #7 on: April 08, 2020, 03:22:19 PM »
 I fixed the typo, yes you are all good to go.
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My next bike will be a ..ANFOB.....

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Lost quite a few CB 750's along the way

Offline HondaMan

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Re: Do crankshaft bearing tolerances need to match?
« Reply #8 on: April 08, 2020, 05:32:58 PM »
Those numbers are actually closer than most of the engines I work on, so they will be great!
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Offline Plzhalpimlost

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Re: Do crankshaft bearing tolerances need to match?
« Reply #9 on: April 08, 2020, 10:23:20 PM »
Quote from: HondaMan on April 08, 2020, 05:32:58 PM
Those numbers are actually closer than most of the engines I work on, so they will be great!
Thanks Hondaman! I appreciate the reassurance.


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