I rather like to watch old Seinfeld episodes once in a while and noticed yesterday in a shot where he was standing close to the bike (the one hanging in his hall) that it actually didn't have a chain on! I think this episode was titled 'The Seven' (or maybe the one before?) and for some reason looked at the timer and it was around 6m30s into the episode.

If you search around you'll find various stories about Seinfeld's bikes, but I don't think anyone noticed this before