@Foosa
I might be wrong but as per my info in oil cooled systems oil is always fed from Sump to Oil cooler & cooled oil is fed to head so it shudnt be possible to fill water instead of oil. In these engines the oil working as a coolant is same which is used for engine lubrication no extra or diffent oil is used for cooling system.
@Stylishkiller
Which model of CBR 250 u r talking about is it Aero Or RR?