You're really kind of guessing as to whether you have all the water out of the system or not, but there are various ways to do it including steaming it out (be very careful with this option). The prep fluid they sell is probably the best & safest alternative for most folks, but I've never used it. I simply drained everything I could out, tipped the bike every which way, blew my system out with compressed air and let it sit open for a weeks or so to let anything else evaporate and then installed my NPG+. Another option that I've used for a friends KX250 & another XR650R was to drain as much of the coolant out as possible via the drain screw in the pump housing with the help of radically tiling the bike over, etc. Then I let it sit for a day with the cooling system open in hopes some more water may evaporate. Then I filled it with Evans NPG+ and ran the bike for 20 minutes to get it good and hot and drained as much of the NPG+ coolant I could. I figured this would greatly increase my chances of removing most if not all the old water/coolant and then I refilled again with the remaining new NPG+. The bike has run solid for a few years now except for my brother-in-law bending it to pieces I should also note that I'm on the west coast (warmer climate) and that I do not run a T-Stat in my bikes. The 650R t-stats are known to stick open anyway (as mine was). The NPG+ is definitely more vicious than something like HP Cool. This higher viscosity can be a problem with some applications (certain automobiles), but I've never found it to be an issue with the XR650R or some of the other bikes I've used it in. I woudln't go so far as to say it works well in all bikes because I've not personally tested it in a YZF or KTM, etc, but I've read reports from others who have. I would still use the overflow bottle and fill it half full. I keep it there as my spare NPG+ incase I ever get low It may be great for a SM application, but if you're racing it on a track, you'll need to make sure the coolant you're using complies to your tracks requirements.