SOHC.co.uk Forums > CB350/400

400 - “elasticity” in headnuts

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royhall:
We're back to this oil don't oil the threads debate. If you did a full rebuild the threads would be dry on assembly, if you did the head on a bike that's run all the threads will be oiled and there's not much you can do to remove it. What's the correct torque for oiled threads because I suspect we are all doing it wrong on repairs?

Erwin83:

--- Quote from: Rob62 on July 08, 2020, 11:55:39 PM ---I just don’t get why you would torque the bolts in the “correct order” but to the wrong spec? If you’re going to use a torque wrench surely you need to check what value to set it to....otherwise why bother, you might just as well use any old spanner.... ::)

--- End quote ---

You never make mistakes?
I only have a workshop manual of a 350f, so for the 400 I searched and found a torque spec of 29 Nm. Must have been the wrong bike or the wrong source.  :-X

royhall:
Your not the only one, I make mistakes constantly. Sometimes repeating the same mistakes over and over. It's the price I pay for getting older, just have to check and double check everything I do. Mistakes happen to everybody at some point.

Bryanj:
An old bosses saying was

" Him what don't make a mistake don't do bugger all"

K2-K6:
"The studs obviously work the same, but I’ve never actually seen it like this.
By the way, going from 25 Nm to 30 Nm is not even 1/8 of a turn of the nut. The ‘stretching’ of the stud is therefore pretty minimal, should that come into play."

It's difficult to feel any changes this small, but if you pull this type of thing on a test rig they start a very benign stretch first,  followed by a big bang as failure comes fast, you just can't separate the phases as its such a small dimensional change.

It's that angle change multiplied by the thread pitch that gives more elongation as the stud top travels away from it's base fixing point.  The change is distributed over the entire length though (as Honda designed it properly with waisted central section) but we don't know a yeald figure at which point the material stretches beyond elasticity, making it a guess as to how close you got. 

I'd try them again after running for a while exactly as you've done now "see if they turn at the correct maximum torque rating" and not release/ reset them. If they are still holding torque ok (you can't separate gasket squish from torque release to clearly see) then they should be ok to leave alone.

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