my rst never really gets that hot,never more than half.it seems to be workin fine.However sumtimes after i stop and switch it off it bubbles up through the header tank . ive been told its because its got a standard header but runs bout 200bhp,is this is?or is it serious?

 

It do sound like its getting prety hot try changing thermostat might help its not any thing to do with what header tank you have.