losing coolant

my buddies kfx450 is losing a lot of coolant and fast. there's nothing smoking and cant find a leak anywhere. at this point he's added so much that if it were dumping into the motor that the motor would have been locked up by now. anyone else had this probelm? any ideas?

Thanks

I Have seen this before as well. The KFX does not have a mechanical thermostat in the head and NEEDS to be filled and burped for air pockets in the engine. if you have any air in the coolant system you can blow a ton of coolant out of the overflow. Fill the radiator to the top then lift the bike up by the bumper and bounce it up and down and you will see the coolant bubble air out of it if you lift it high enough.Add more coolant and repeat this untill you can not see any more air and the radiator is full. that should help. thanks. Jeff @Walsh RC.

thanks man! this info came just in time, we have a xc race tommorow. we'll give this a shot tonite and see how it goes.

blown head gasket is a possibility