Big engine/small cooling system. You can't keep a 1.7 liter engine cool with a two quart cooling system. There is no magical additive that's going to make a noticeable difference on the bike.
Once you stop moving the cooling system is quickly overwhelmed and you feel the radiated heat. If someone could design air deflectors that mount to the side of the bike which could redirect the air flowing around the bike towards the engine and rider that would help.
2010 Voyager 1700 ABS with heated seats, Grasshopper backrest, Kuryakyn highway pegs and an Ipod because the radio reception fades in and out. Also has a gear whine, fuel gauge that fluctuates too much and a pathetic cooling system.