Guys, Got to the track on the w/e, noticed the coolant was a little low on the YZ450F (2008), so decided to top up with tap water (nothing else around), about 250ml (cooling system has a 1 litre capacity) and rode for about 2.5 hours without any boiling/overheating. Level stayed constant throughout. Should I now flush the coolant and replace with de-mineralized water? The manual states a coolant/water ratio of 50/50. Shops also sell pre-mixed coolant (ie. http://www.supercheapauto.com.au/online-store/products/Tectaloy-60-Plus-inhibitor-5-Litre.aspx?pid=1053#Description). Would this stuff contain the right mixing ratio? Or is it best to buy some demineralized water and some of this stuff: http://www.supercheapauto.com.au/online-store/products/Calibre-Anti-Freeze-Anti-Boil-Concentrate-1-Litre.aspx?pid=155034#Description and mix it myself? Also out of curiousity, how long does tap water take to start corroding the internals? When flushing the radiator, is it just a matter of draining, and pouring tap water into the radiator until it's fully flushed out of the drain bolt? (clear water coming through), then topping up accordingly?