I just bought a 2007 WR450F and wanted to start buying parts a little here, and a little there so I can have all the parts ready when I need them, and so I don't have to buy it all at once. My question(s) is: 1) What parts do I need for a top end? I know I will need piston kit for sure. I also will probably do SS valves (with the SS specific springs) swap at that time. What about spring retainers, stems, seats, lifters (buckets) etc... 2) Is there any special process to swap in SS valves/springs? If so, is it the lapping process? I think those are my major questions right now. Thank you.