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No, you need to identify the colour used, there are 5 colours for the 400, black, green, brown, yellow and the 400 has a blue that most don't have.As I previously said, see if any remnant of the old colours are still on the edge of the shell, green shows up pretty well for instance. Check the crank journals for scoring, with the state of that bearing I'd be worried about the journals, run a fingernail across it and see if you can feel anything.
Buy the shells from Yamiya Ted if you can't find them locally. You don't have cranks ground on these engines just to make shells fit. This isn't a Ford Anglia 😁😁😁PS What's a Ford Anglia is it like Ford Prefect.
You need to be able to measure accurately to at least 2 decimal places in metric(0.01mm=0.4thou) so not within verineer acuracy im afraid. May be cheaper to get in done by somebody used to micrometers as the acuracy "feel" is an aquired art
TED CMS still sell most of the main bearings, I was wrong as well, there appears to be a Red bearing as well, no blues or blacks but do have Brown, Green and Red. Brown and Green are the most common colours. Click on a bearing and you can see the colours on the edge of the bearing so you know where to look.https://www.cmsnl.com/honda-cb400f-england_model14639/partslist/E01.html#.YFcwHVX7SUnNo 42 for mains, No 40 for conrods.
Whatever you do Ted don't mix the shells or forget where they came from.As Julie says that definitely a green, so that journal requires a green pair of shells. You could use the back of the shell markings and see if the one you've identified is the same as the rest. They tended to use the same marks for the same colour for the same production run, so if any other shells match that marking it's reasonable to assume that's a green shell as well. The conrod shells use the same method so check the side of those for colours as well.