2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

rotor bearing ? how much copper is bad?pic inside

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Old Apr 8, 2012 | 04:01 PM
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RI rotor bearing ? how much copper is bad?pic inside

before starting putting my motor back together i want to make sure this rotor bearing is still good . its from a 88 turbo 2 with 42k on it . my old ones have 92k on them . let me know if u guys think i should change them . i dont have the special tool to do it . theres no rough feeling on it at all . all the other rotors are perfectly fine just this one.
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Old Apr 8, 2012 | 04:17 PM
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Originally Posted by bmwrx7man
before starting putting my motor back together i want to make sure this rotor bearing is still good . its from a 88 turbo 2 with 42k on it . my old ones have 92k on them . let me know if u guys think i should change them . i dont have the special tool to do it . theres no rough feeling on it at all . all the other rotors are perfectly fine just this one.
What's the clearance against the eccentric shaft? What are you running for an oil pump and regulator?

The "copper showing means replacement" ideology is a myth. The babbit surface is there only to lubricate during dry starts; when the engine is running, the surfaces of the bearing and the eccentric shaft are completely separated by a film of oil, so it deosn't matter if the rotor surface is babbit, copper, or iron.

On race engines with high oil pressure and oil flow, I've completely removed the babbit surface with no ill effects.

This doesn't mean its ok to run; you still need to check the clearance. But you can go ahead and ignore the colour of the bearing.
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Old Apr 8, 2012 | 06:31 PM
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i guess im running everything stock the motor always had high oilpressuse . never leaked or anything . but since these rotors were off a "42k" turbo 2 they should be fine. the other rotor looks mint they both do . so im wondering how to check the clearence to the shaft then
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Old Apr 9, 2012 | 10:38 AM
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anyone else??
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Old Apr 9, 2012 | 12:16 PM
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Get a factory service manual for the rebuild.
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Old Apr 9, 2012 | 12:56 PM
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i have the rebuild video . but i dont have them tools to mesure that clearence .
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Old Apr 9, 2012 | 01:27 PM
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Looks fine, industry standard is like 20% of copper showing IIRC. I would go ahead and reuse that bearing. But definitely check rotor to eshaft oil clearance.
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Old Apr 9, 2012 | 02:19 PM
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you'll want to check all your clearences as per the FSM tear down or rebuild DVD. You are going to need feeler gauges, a micrometer, and caliper. a height gauge would be useful as well but are expensive. Mayb you can rent the tools form your local equipment rental place or an auto parts store. here's aaron cake's rebuild of a 6 port engine but a 4 port block is the same, just use appropriate gaskets for your engine. 13b blocks are virtually all the same at bare block level when assembling.

<iframe width="420" height="315" src="http://www.youtube.com/embed/ijJeUk_GqiI" frameborder="0" allowfullscreen></iframe>

and to emphasize, do check all your clearences for housings, bearings, etc. else whats the point in rebuilding it?
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Old Apr 9, 2012 | 04:57 PM
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i did check most of it . most the parts i brought came from a good running t2 only thing i really messed up was one rotor and housing on my old motor . i have a feeling that motor that was in my car was a reman or something everything looked to clean and came apart easy
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Old Apr 11, 2012 | 12:08 PM
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any 1 else? im gonna put it on the eshaft later and see
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Old Apr 11, 2012 | 12:27 PM
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I personally would not use them, all the regular piston engines and even my first rotary got all new bearings no matter what.I think of it like this,would you reuse the water jacket seals?
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Old Apr 11, 2012 | 01:19 PM
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nope i wanted to get new ones . a local rotary guy says if there fine you dont need em . personally i wanted todo them myself .but that tool to press em out isnt cheap . but i might just have todo it since i didnt cheap out on anything else . but since i seen him build alot of motors himself nothing wrong with any of them i took his word for it
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Old Apr 11, 2012 | 01:40 PM
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Its really coming down to a matter of opinion. Industry says that passes, i would reuse it. No doubt that wouldnt affect oil pressure at all, unless the clearance is excessive. But by the looks of it just a bit of the babbitt is gone. Should be okay, if your paranoid abouy it just replace it.
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