[Mike Mason]

Just removed the valve guides from my 1960 Super Meteor and there is a bush fitted in the heads to take the guides. Is this standard? I`ve just measured the guides at about 0.610 which is a lot smaller than the standard size. I will re-measure with a digital vernier but I cant be that far out.

[Dantheman]

This would not be standard, the valve guides would just be a direct interference fit into the cylinder heads originally. The aluminium in the head can wear over time as the guides are fitted in and out, and usually an oversize guide would be fitted to resolve this, all though with your engine it sounds like a previous owner has used another method to get around this.

Workshop manuals are now available as a free of charge download, within this you will find the specifications which might be of some use:
https://accessories.hitchcocksmotorcycles.com/Workshop-Manuals-To-Download