if there was no antifreeze in the cooloing ststem it will most certainly do that and can even crack the barrel or crankcase or head in half.if they ahve it in bits gt them to leave the thermostat out they cause endless problems on these bikes and end up ruining them,it may just take a minute longer to warm up when its cold but it will save you £ in the summer when it stops opening up.trust me seen it many time before.
adam bike doctor(of milton keynes motorcycle centre)
January 2011