I am getting MX 22 inch tires for my X. I am going to go from a 13 tooth in the front to a 14 for better top end. I also want to get a smaller rear sprocket. (38 or lower) but Rockymountain, ebay, and denniskirk all have no rear sprockets besides the 40 tooth ones. Should i find like a 250x rear sprocket or something that keeps the 520 chain and just buy a 38 tooth or spend LOTS of cash that i DO NOT have on sidewinder custom sprockets? My X does 65 now with this gearing how fast will it be with the 14/38 gearing? Also i am going to be putting a 400ex carb (once i get one real cheap of eBay) i have a 450r silencer(as of today). You think i can hit about 70? Thanks! Cragster