SOHC.co.uk Forums > CB750

New Main and Big End Bearing Shells

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adriangsmith:
Hi OddJob,
K is the heaviest weight and this is an F2 engine.
according to the chart i have the mains should be a letter/letter combination as shown here:
http://www.hondachopper.com/engine/diagrams/images/crank.parts2.gif
where the conrods shoud be a number/number combination as shown here:
http://www.hondachopper.com/engine/diagrams/images/crank.parts1.gif
Please correct me if im reading this wrong.

So mains would have been all greens
And big ends would have been all greens also

Based on the wear measured on the journals should i replace them all with blacks?

Trigger:
From the pictures the crank looks finished on the first picture but, hard to tell unless up close and personal.

Trigger:

--- Quote from: Oddjob on May 23, 2016, 07:30:25 PM ---As Trig says it is hard to make a determination on the state of the crank from pics. However try this and see what you think.

The centre mark in the main journals is where the oil groove runs, you'll see on the shell that it has a recess there to allow oil to spread across the shell, as this part doesn't touch the crank journal it doesn't wear it so if that centre section is higher than the rest that shows the crank is quite worn. Just because they are shiny doesn't mean they are worn, run a fingernail across the journal and if there is a ridge where it meets the oil groove then you'll have to think about a replacement crank.

--- End quote ---

Zoom in Ken and tell me if my eye sight is going but, I see more pits than a teenager getting over acne

adriangsmith:
Thanks all,
No pits on the crank shaft just the faint score lines.
I'll give it a wipe over and take some more shots.
Big thanks for the service bullitins Ash, very informative.
Adrian

adriangsmith:
cleaned and checked. no obvious ridges on the mains but they feel a little rougher than i would expect.
Also included an image of the old main shells, all of them worn pretty much the same as these.

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