The nightmare after Christmas.
Back to the K3 build now its warm enough to go back in the garage. Assembled the clutch and along with the clutch components is a spacer 25mm ID, 4mm wide, 1.4mm thick. I assumed this sat on the clutch shaft but doing a dry build it obviously doesn't.
Had a quick look in the parts book and the only spacer I can see that looks anything similar is 28112-323-000 spacer 25mm on the primary shaft. I have no reason to believe it has been missed out of the engine build but any other possible location suggestions very welcome.