I think this was addressed quit a while ago, but I couldn't find it in the archives. The last two rides I've started loosing radiator fluid. I'll fill the reservoir to the full line and by the end of a 30-50 mile run it will be at or below the add line. My riding area and habits have not changed. I drained the oil but could not tell if there was any coolant in it. I've not noticed any change in the bikes performace nor fluid leaking from the bike (other than the normal oil coming from the breather tube). I don't know if this will help, but here are some specs on my bike and riding habits: RIDING HABITS - 1 to 2 times a week in the Arizona desert. About 4,000 miles on bike now. Was at Baja with Richard in March (see the "Stories" section) BIKE - '99wr400, air box lid off, FMF mega MaxII (uncorked), modified throttle stop, IMS tank&seat combo, applied top triple, Scotts Damper, maintained well (valves,linkage, oil changes, etc.) Thanks for your help with this one.