In case you´re still looking: The ´83 CX650 Custom didn´t have a key for releasing the seat. The seat is held on with the forward pair of bolts that mount the rear grab bar. The bolts then go through "spacers", the fender, and the seat brackets, and on into the frame. Don´t lose those spacers, they are no longer available. The key should fit the helmet lock, gas tank lid, and the document box attached to the rear grab bar. I had a key made from the lock on the grab bar box, but you´d have to break that to get the lock out; you ought to be able to get the number from the helmet lock without breaking anything.