400 seems truly exotic. Can't find a single one (for sale or show) in the neighbourhood. Guess finding 400 specific spares would be a nightmare. Pity, since it sounds like perfect bike - just a bit lighter than 600, probably less thirsty and lower taxes. BTW, this spill check rally works!
Just came accross this when searchinghttp://www.ebay.co.uk/itm/Yamaha-FZ-400-4YR1-96-EBC-CK2371-Clutch-Kit-/150696962004?pt=UK_Motorcycle_Parts&hash=item23163d27d4