[Boring]Yup, it would appear that as they're OEM forks the shim that allows the oil through slowly to give the rebound damping is nylon rather than metal, and has disintegrated. No problem, TF sell metal ones for £3, on further inspection it turns out that the reason the cartridge appeared 'siezed' was that the previous owner had wound the damping up (post failure I suspect) enough to destroy the nylon valve assembly inside the cartridge, rendering any repair useless! AAAAAARGH!!![/Boring]
David, is the manual you have the proper workshop one, or the one that comes with the forks? As the workshop one has exploded diagrams and part numbers in it for the internals, which the supplied one doesn't (I have 3 sets of z1s from 2003 to 2005 :wink:)