hi kenny,
welcome to uhe. the 99 fe400 is generally a solid bike with few issues. if the fe400e with elec start, it will have a counterbalancer that on occasion causes problems. it will sound louder than the fe400 without it. the kickstart and the estart model bothhave the sem ignition that periodically eats stators (expensive fix). wouldn't hurt to pull the mag cover to see if things look clean, not corroded. all the dellorto carbs tended to wear the needle and needle jet which made them run poorly at 1/4 throttle and above, especially at throttle changes. (easy fix). other issues are the same as any used dirt bike. mostly these bikes give you alot of bang per buck.