Hey guys. I just bought a 2000 WR400F and just started riding as well. When I ride, the bike gets real hot. So hot the coolant boils. Also, the coolant does not return to the engine from the overflow tank when it cools down? I don't know why this is. The radiator cap makes a suction/popping sound when I pull it off after the bike has cooled down, maybe I need a new one. I have a White Bros pipe with the jetting at a 168 main and a 48 pilot. I have a JD needle (blue tip), third position down. 2 1/2 turns out on the fuel screw. Right now, the TPS is disconnected until I can replace it with a new one. I don't have cash to just buy a brand new bike like some of my riding buddies are suggesting. I want to ride, but I don't want to blow up my bike either. Kind of a catch 22. One of my buds suggested using coolant with a higher boiling temp. Does anyone know of any? I ride around 4000-8000'. Any help would be killer.