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She go poof.
Posted: Mon Jul 12, 2010 12:33 pm
by cbmanx
Some good advice required. My 79 CBX has died. On removal of the engine and strip down I have found the bearing shells have all turned in the big ends and the number 4 is completely shot. It would appear that the previous owner has had some very poor repairs done to a "knocking" engine and although the main journals appear to be standard, the big ends appear to have been ground and shells that "fit" have been fitted. Is this now a junk bottom end? What are the standard journals sizes so I have somewhere to start from? My service manual has some very complex sums to do for oil clearances but no starting point sizes.
Thanks for any help in advance.
Re: She go poof.
Posted: Tue Jul 20, 2010 7:27 pm
by alimey4u2
Crank bearing areas can be built up, as long as the mains are OK... but one must consider also the cost of a used ( in good shape) crank compared to a rebuild....
Give us the data on the crank, the crankcase, rods & we can decode it for you.... As long as regrinds have been logged. If not, a micrometer must be used...
First question...Anything spun in the alloy ???
Re: She go poof.
Posted: Mon Jul 26, 2010 3:47 pm
by cbmanx
Nothing has spun in the alloy. The best journals are 35.92mm, the worst are 35.6mm. According to the book the smallest should be 35.976mm.
the rods are gone. 39.80mm says to me that they have been bored out to suit the new shells. I do have another engine with the same wear on the crank but good rods. Would it be better for me to find a better engine or stick with these two and make one good one? Is it worth rebuilding the crank and where to get it done?
Re: She go poof.
Posted: Tue Aug 03, 2010 4:21 am
by alimey4u2
cbmanx wrote:Nothing has spun in the alloy. The best journals are 35.92mm, the worst are 35.6mm. According to the book the smallest should be 35.976mm.
the rods are gone. 39.80mm says to me that they have been bored out to suit the new shells. I do have another engine with the same wear on the crank but good rods. Would it be better for me to find a better engine or stick with these two and make one good one? Is it worth rebuilding the crank and where to get it done?
Sorry for the delay in reply, the sun has been out....
My feelings are the two engines you know (as you've been inside.) It may be less costly to make the two ... one. As for crank building, Falicon in the States are superb. Not sure about these shores but let me see what I can come up with...
Re: She go poof.
Posted: Tue Aug 03, 2010 4:37 am
by alimey4u2