I put a new chain & sprocket kit on my old (1985) FZ750 the other month and decided to put a new locking washer & nut on at the same time,I just phoned Granby Yamaha and they posted it.
They know their Yamahas, I had to order 15 shims a few weeks prior to that £75!

.With a bike of that age the local dealers were'nt any use but Granbys got me sorted,they're about 120 miles from me so it was all done over the phone.