All I have to add that others haven't already is if you don't like the price or how the bike runs on castor 927 I highly recommend Amsoil Dominator. Its good stuff and half the price of 927 that's what I run in all my 2 strokes.
I like foam filters but I am in mud/dirt/dust not sand and I think that's where K&N are better? Not sure.
For bottom end oil I use ATF type F and others will suggest it too. You need to change it more frequently though.
Powder coating is WAY more durable and looks nicer but also cost more$$$.