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Help with bearings

Old 01-29-2006, 05:19 PM
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Help with bearings

Hi everyone.

I am rebuilding my engine at the moment and have found that the bearing shells for the conrod big ends are different from front to rear. The rear conrod bearing set has a larger oil hole in it than the front conrod bearing set by about 20 thou. The smaller set is actually smaller than the oil gallery hole in the conrod, and will restrict the flow. Honda in Aust are not able to tell me if this is correct or not, which I think is pretty hopeless. We are a small country though I guess.

Can anyone who has done a rebuild tell me if this is correct? I am concerned I may have a wrong bearing set.

My bike had a stuffed engine when I bought it, and the problem was a stuffed conrod bearing, so I am a bit worried! Do these engines ever normally suffer from bearing failure?

I have also found that with the new transmission shaft splined bushes that I have, that the oil hole in them does not line up perfectly with the oil hole in the shaft. Half of it is off centre. One of the old ones I took out is the same, but the other two old ones were ok. It seems that these Honda parts are all a bit different. Is this something that needs to be perfect? If it is production tolerances that are to blame and they are not perfect, should I drill the holes to a lerger size so the oil is not restricted?

Cheers,
Shayne
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Old 01-30-2006, 02:06 PM
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Re: Help with bearings

I finally found someone at Honda who could answer this.

The bearings are OK. Front and rear cylinders are supposed to be different. Both big ends are fed from the same main bearing oil galery and the oil holes in the bearing shells are a different size to equalize the oil pressure for each rod.

Transmission shaft bushes are only a secondary oil feed, as most lubrication is done by splash, so as long as part of the hole is open it is ok. Rounding out the holes will not hurt however.
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