99 recon 250 rebuild

What do you guys recommend replacing or checking? We’ve had it for maybe two years and done just the basics. Started smoking real bad on Halloween, so it’s big maintenance time. I already have half of the motor torn apart and plan to do the valves, piston, and rings, rebuild the carburetor, new brakes, and rear bearings. As far as I know, everything on this is 20 year old originals.