this sounds to me like the pressure cap is knackered,, water boils at a much higher temperature when under pressure so if you are losing the coolant through the overflow but not seeing bubbles in the coolant then i reckon your pressure cap is either not seated correctly or is knackered.
i had a gpz900r that i bought really cheap because the head gasket had gone. i changed the pressure cap and it was absolutely fine 8)
any chance you could borrow a cap off anyone? just to see if its this? where are you at?
if you're close you can borrow mine to test it
i had a gpz900r that i bought really cheap because the head gasket had gone. i changed the pressure cap and it was absolutely fine 8)
any chance you could borrow a cap off anyone? just to see if its this? where are you at?
if you're close you can borrow mine to test it