tear it down too the bare frame, there are alot of tabs and things you can cut off of it to save alot of weight. if you dont have alot of FAB skills, get an aluminum or bolt on chromoly sub frame.
what size motor are you looking for? if you still want stock cylinders, get a 4 mill crank and get ur cylinders ported to match the crank and pistons.
adda cool head of some sort, i have a D&D racing head, but there are ALOT of good ones out there.
get an override tranny, prolly 2-5 with manual 6th gear.
aftermarket swingarm, alot of SPONSORS on here that make amazing parts, look through the sponsors list before checking ebay (ebay is a last resort for a drag build)
lightweight set of a-arms and some lightweight short shocks.
lightweight narrow axle
either hoosier or american racing tires on douglas blue label rims
while you build all of this back together, start throwing alot of the stock parts and things over your shoulder as alot of what YAMAHA put on the bike is not needed for a drag bike..