Be sure to put some wax or something on that chrome so the oxide doesn't bloom up again!
Did you rebuild the coaster hub? I recently started mechanically refurbishing a '74 Schwinn Stingray a friend sold me, and it's quite difficult to pedal. The hub is the last thing I have to regrease on the bike, so I'm wondering if you might have a similar problem.
Or it could just be the single speed
