Wr 400 Overheating!!!

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.

A couple of options here:

-The coolant is not the right mix. Maybe the previous owner just added water instead of a mix of water and ethylene/glycol. Just drain it all and replace it.

-The circuit needs pressure to work, so if you have a leak, it will not cool properly. this also would explain why the coolant is'nt flowing back from the overflow tank (you need a closed circuit and under pressure for that). leakage could be at the radiator, the hoses, the cap, or inside the engine. If it's the radiator or hoses, you would see water dripping when you stop riding. The radiator cap being no longer functional you would hear a hiss when the engine get's hot (before taking off the cap). Finally, if the leak is in the engine, in most cases you get a white smoke coming out of the exhaust, or water in the oil when you drain the engine of it's oil (milky oil). Dealers have a special tool/pump to test both the cap and the circuit pressure.

-Last but not least, the water pump might be broken. If you don't have any of the symptoms above, this would be the most obvious reason. What I would do (not sure this is the right way) is drain the liquid, remove the water pump housing, and check the bearing, shaft and impeller for damage. Move the kick starter slowlt to see whether it turns OK.

Most of these problems are easy and cheap to fix, except if the leak is in the engine or the impeller shaft needs replacement. In these cases you need to take the engine apart. A leaking radiator you can either replace (expensive) or have it welded (cheap)

Hope this helps...

Hi mate I have a 2000 model wr 400 and it gets real hot. Especially if your in low gears bashing up the snotty hills. It gets hot when you cake up the radiators with mud. if you just idle for a few minutes without moving it gets real hot. Every time I take the radiator cap off you cant see the coolant unless you tip the bike on its side. But its always been like that. Ive got used to shutting it off when waiting for mates to catch up or stuck on a hill.

Replace the coolant to be sure you have the right mix, there are also higher boiling coolants that you can try, but I have no problems with my 400 unless really slow going on really hot days (which I avoid doing anyway). If you have suction on removing the radiator cap, probably no leaks, but you should check the hose going back to the overflow bottle, may be pinched. Happens easily. Good luck

I had a '98 YZ400 that would boil over on long rides. Turned out it had a blown head gasket and the head was warped.... I would suggest pressure testing the cooling system before throwing money at it anywhere else.....

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now