When I fill the expansion tank the coolant goes into the system and after a long run it is spurting out of the overflow. The system requires filling again but there is no sign of a leak even when the bike is stood still. I am just the messenger on this one, it is my son who has the bike.

Les, July 2011

head gasket mate these kawasakis always blow gaskets i bet it piss's out just after you have parked it up and leaves a nice ltle wet patch on the floor,it does this because the air that leaks past the heads combusion chamber part of the gasket goes into the water jacket and raises the pressure and pushes the excess water out into the header tank its this pressure and raised volume due to the air(leaking burnt gases) that psuh it out.i have done loads of them on zx6's zx7's zx9's and zxr750's and zxr400's they all suffer from it its a kawasaki thing.

adam bike doctor(of milton keynes motorcycle centre), July 2011

Hi Les, are you topping up with the correct coolant/anti-freeze mixture using de-ionised water? if not i'd drain the system and refill with the correct coolant mix. sorry i don't know what the ZX takes but could be something like a 50/50 water/coolant,anti-freeze mix. If that doesn't do it your son may have to take the bike to the bike shop for a coolant system pressure test.all the best.

Ted, July 2011

SD.
Maybe I should have been more explicit and not used the word fill, topped up to the mark would be more appropriate, common sense dictates that if you fill anything then it will expand and vent itself.

Les, July 2011

Just a thought, I am not an expert on bikes.
You say expansion tank. If you fill an expansion tank, it has nowhere to go when it expands, due to heat, so it would come out. I would suggest a read of instructions, as to what needs filling to what.

SD, July 2011