That is a very good question, I suppose if there is a bush in there it can be removed and another put in, I don't recall seeing any mention about this anywhere but will start looking as it is relevant to us all.

A bush does sound unlikely as the loading at that point is not great, Honda's trick of running it in the casting would do but does that bit get any lubrication.

As I've not seen in there I can't say but just about everyone else in this forum will have had the valve out I would think.

Cheers D.