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Cylinder bore assessment

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daz-j:
Hi all, I'd be grateful for a little advice please on assessing the condition of the cylinders, as I have no previous experience of this.  I've measured all 4 bores, each in 4 positions.  Each one sizes up the same, slightly oval at 51.03-51.05mm - so to my understanding that's within the service limit.

All have what I would say is light scoring, which can be felt with fingernail - the photo below is probably the worst case.

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Would this be regarded as acceptable condition, a candidate for re-honing, or even reboring?
Thank you.

Nurse Julie:
If you can feel the scuffs with your fingernail, it needs a rebore. You should not be able to feel anything at all with your nail.

Bryanj:
I have seen worse run but its not ideal, re ring with ade glaze would probably get you about 80% compression after settling in, to be a "good" job needs oversize kits and rebore which costs, its your money and time so your choice, personally i would bore it

Skoti:
Yep,

agree with what's been said above, but here's another option available to you.

Low mileage second hand barrels and pistons here:-
https://www.ebay.de/itm/Cylinder-Compl-With-Piston-And-Rings-Cylinder-Piston-Rings-Honda-CB400F-Used/265053325887?hash=ite

I can recommend this place, they are sort of like the German version of DS, but they also import low mileage bikes from the states and dismantle them for spares.

I bought CB750 barrels and pistons from them which were in excellent condition and ready to fit with new piston circlips.

They speak perfect English, so you could contact them and ask for close up photos of the cylinders etc.

 
 
 

philward:
You can get a set of quality oversize piston/rings from Cruzinimage for about £120 plus the rebore cost - much cheaper than SH set

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