there is few drum rear wheels for 85 kx125 on ebay right now. my first motocross bike was a 85 125, currently restoring it, must have owned 10 different 80's era kx125 when i was younger. i remember just about every one i owned had powervalves not in right. not sure of any must do's, but all of mine really took to port work, and head work. i just remember 84-87 had vm 34 mikuni that had no air screw. i had to tap the thing and rob parts from yamaha models to make work. usually went leaner on everything in carb. if you need any parts, i have alot of 125 stuff i won't need for my build.