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Discussion Starter #1
Does anyone know the sizes of the different colored main journal bearings? And I would appreciate if anyone could give a good description on how to get the correct size. Thanks
 

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Why are you checking bearings? Fry the engine? are the cases screwed like mine were? You may be in for a lot of money....

SEARCH online or maybe someone here has the service manual...I believe there are black brown green and possibly other bearing codes.....have to check the code on the cases as well and mic the crank/rod journals....

I believe they recommend 0.0012-0.0019 for clearance...

Start with the service manual.
 

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First off you should have the factory manual if you are this deep into the motor. Actually the ideal combo is Hondas general service manual, the RC51 factory manual and maybe a aftermarket manual to translate the "Honda Way" for those unfamiliar. That being said, I'm here to help. Main journal code ( numbers 1,2 or 3) is found on the crank weight. the crankcase bearing codes are on the left side of the upper crankcase. Will be an A,B or C. Refer to chart on page 12-5 for selection of yellow, green, brown, black or blue bearing. After you clean the bearing area, use Plastiguage to check the oil clearance. Main journal clearance is .0008" to .0015".
 

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I bought an engine for my track bike and I pulled it apart just to see how it works. The main bearing codes are 3,3 and the crankcase bearing code is C,B. I downloaded the service manual, but I'm still confused on how to use the codes.
 

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O.k if you downloaded the factory manual at the bottom of 12-5 there is a chart. The 3 bearing support id codes are displayed horizontally A, B, C. Then you see the 3 main journal O.D. codes vertically from top to bottom, 1,2,3. Looking across the 3 row you find the black bearing under the row B. Under the row C you find the blue bearing. Also I didn't state on my previous post that the code on the left crank weight will be for the left crank bearing and first letter code on crankcase is left code and so on.
 
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