Bleeding air from cooling system

Mar 25, 2001
I am in the process of rebuilding a 99 kx 250 for a friend and i have the motor all together and i was wondering how to bleed the air out of the cooling system when i poor the coolant in. I know on my KDX that there is a screw at the top of the head but this doesn't seem to be the case on this bike. I was wondering if i should just pour it in, run it, then top it off, or if i should fill it then take out one of the drain plugs until coolant starts to come out then put the plug back in and top it off. any help is apreciated and i need info my tomorrow morning cuz it will be running then one way or the other.thanks


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Sep 3, 2001
I've always just filled it up, let it run a bit, then checked and topped off as needed.  Some times if you tip the bike around a bit, away from the side the cap is on, it will gurgle a bit allowing more to be added.

As long as the pump has a supply of coolant, it should force any air out of the system and up to the top of the radiator.