The seat is securing by two bolts, and the seat latch.
The seat bolts are a 5mm hex head bolt on the bolt
side, and 10mm on the nut side. Avoid overtightening
or the seat will not be able to be lifted easily.
The headset bolt is a 12mm on the bolt side, and 14mm on
the nut side. Turn the handlebars to either side to be able to
gain access to the nut side.