You don't really need a 225 cylinder, you can also use a 225 sleeve in your 200 cylinder.
You can keep your clutch. 5 disks are good for 225ccm.
- 225 crank
- 225 piston (70mm is std, available up to 73mm)
- 225 cylinder or sleeve
- gaskets (foot and head is minimum)
- bigger case opening
And don't forget to rejet the carb.