I have used water wetter in my past track bikes and will use it again when my RC 390 becomes a track only bike. It is basically a surfactant that lowers the surface tension between the walls of the cooling passages and the cooling water. This gives better (faster) heat transfer between the two. There is something most of you are missing on this thread. Internal combustion engines are very thermally inefficient. Most of the energy generated during combustion escapes out the exhaust after pushing the piston down. But as the piston is moving down under expansion, energy is also transferring to the cylinder walls, heating them up. This heat transfer takes energy away from pushing the piston down, robing power. Modern engines are designed to run hot, well above the boiling point of water at atmospheric pressure. This high operating temperature slows the heat transfer from the expanding gas to the cylinder walls, leaving a bit more energy to push the piston down. It is a small improvement, 1-2% but on a small motor like the RC's it makes a difference. So your goal should not be to get the bike to run cooler but to get the bike to work at the temperature it was designed to operate at with out puking its coolant all over the place. That is why the best upgrade is a higher release pressure radiator cap and running a coolant mixture that is mostly water and less antifreeze. If you have a lot of slow or stop and go riding you need to look at getting the radiator to get rid of waste heat better, but keep the ability to run as hot as possible when you want the most power from your bike.
